compost use in florida - florida department of environmental

Compost Use In Florida

Produced by the Florida Center for Solid and HazardousWaste Management for the Florida Department ofEnvironmental Protection, December, 1998

Printed on recycled paper ~~~

Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Figures and Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

IntroductionBeyond the Backyard Compost Pile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Part I: The BasicsChapter 1: Compost and Waste Management in Florida.. . . . . . . . . . . . ~ . . . .9

Mitch Kessler and Allison SearccyChapter 2: What Is Compost? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Margie Lynn Stratton and Jack E. RechciglChapter 3: Developing a Market for Compost Products . . . . . . . . . . . . . . . . 15

Aziz Shiralipour

Part II: Regulatory and Quality Assurance IssuesChapter 4: Regulations Affecting Compost Production and Use . . . .18

Francine Joyal

Chapter 5: Compost and Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

George E. FitzpatrickChapter 6: How to Produce High Quality Compost . . . . . . . . . . . . . . . . . . . . . .24

Patrick D. Byers

Part Ill: Agricultural Uses for Compost in FloridaChapter 7: The Effects of Compost on Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Aziz Shiralipour

Chapter 8: The Benefits of MSW Composts in South Florida . . . . . . . .30Dean Richardson

Chapter 9: How Compost Benefits Citrus Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

J.H. GrahamChapter 10: Growing Field Crops with Compost . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

R.N. Gallaher

Chapter 11: Use of Composts on Florida’s Vegetable Crops . . . . . . . . . . ..39Monica P. Ozores-Hampton and Thomas A. Obreza

Chapter 12: Compost Uses for the Landscape andNursery Industries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

George E. Fitzpatrick and Dennis B. McConnell

Chapter 13: Use of Compost on Turfgrasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45

John L. Cisar and George H. SnyderChapter 14: Compost Use on Forest Lands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48

H. Reikerk

Chapter 15: Reclamation of Phosphate Mine Landswith Compost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

James Ragsdale

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

C O M P O S T U S E I N F L O R I D A 3

.Patrick Byers iSolid Waste Authority :.of Palm Beach ....County, West Palm !Beach, Fla.

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.Thomas A. Obreza !.University of Florida, iInstitute of Food and :.Agricultural Sciences, iSou thwes t F lo r ida i..Research and

...i Education Center, Immokalee, Fla. i

John L. CisarUniversity of Florida,Fort LauderdaleResearch andEducation Center,Fort Lauderdale, Fla.

George E.Fitzpatrick

...University of Florida, i.Fort Lauderdale :Research and ..E d u c a t i o n C e n t e r , [

Fort Lauderdale, Fla.

Monica P. Ozores-Hampton ....University of Florida, iInstitute of Food and :Agricultural Sciences, !Southwest Florida i

Research and Education Center,Immokalee, Fla.

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...Andrew S. Pike (not pictured)Sun-Ray and Southern Farms,Lake Placid, Fla.

:..; R.N. Gallaher ;

~ Department of i.Agronomy,

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University of Florida, :Gainesville, Fla. :..

James RagsdaleSanitationDepartment,City of St.Petersburg, iSt. Petersburg, Fla. i

......J.H. Graham .University of Florida, iCitrus Research and i.E d u c a t i o n C e n t e r , :Lake Alfred, Fla. i......

Jack E. Rechcigl /University of Florida, !Institute of Food and i

Research and

Agricultural Sciences, iRange Cattle

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.Joyal i

Florida Department i..o f E n v i r o n m e n t a l i..Protection,

.....Tallahassee, Fla. i....

Mitch Kessler (not pictured)TIA Solid Waste ManagementConsultants, Inc., Tampa, Fla.

.Dennis B. McConnell iUniversity of Florida, i.Environmental ..Horticulture

....Department,Gainesville, Fla. i.

H. Reikerk....

School of Forest i.Resources and iConservation,University of Florida, iGainesville, Fla. i.

.Dean Richardson i.Reuter Recycling of iFlorida, Pembroke /Pines, Fla. and /.Tropical Treescapes, i.\Miami, Fla. .

Searcy (not pictured)TIA Solid Waste ManagementConsultants, Inc., Tampa, Fla.

Aziz ShiralipourUniversity of Florida,Center for Biomass

Gainesville, Fla.

George H. Snyder (not pictured)University of Florida,Everglades Research and EducationCenter, Belle Glade, Fla.

Margie Lynn Stratton (not pictured)University of Florida, Institute ofFood and Agricultural Sciences,Range Cattle Research and EducationCenter, Ona, Fla.

Produced by the Florida Centerfor Solid and Hazardous WasteManagement, University ofFlorida, College of Engineering,Gainesville, Fla.

Executive Director, John Schert

Technical Editor, Diana Tonnessen

Graphic Design, Production Ink


COMPOST USE IN FLORIDA 6a

ACKNOWLEDGMENT

The Center for Biomass Programs, of the University of Florida's Institute of Food andAgricultural Sciences coordinated the development of the guide by identifying contributors,editing the papers, obtaining illustrative photographs and served as the general liaison withthe authors in developing their papers. Specifically, we would like to note the day-to-dayefforts of Dr. Aziz Shiralipour and Ms. Sharon Thurlow, staff of the Center for BiomassPrograms.

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Figure l-l:

Figure 2- 1:

Figure 5- 1:

Figure 9- 1:

Figure 9-2:

Figure 1 l-l:

Figure 1 l-2:

Figure 12- 1:

Figure 12-2:

Figure 14-1:

Table 3-l:

Table 4- 1:

Table 4-2:

Table 10- 1: Compost Use and Corn Silage Yield . . . . . . . . . . . . . . . . . . . . .38

Table 1 l-l: Physical Properties of Compost used in ..Vegetable Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

Table 13-1:

Table 13-2:

Composition of Florida’s Waste Stream.. . . . . . . . . . . . . . . . . 10

Food Web of the Compost Pile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 ;...Compost Used as a Growing Medium with

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Container Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 ..

Increased Growth of Compost-Treated Tangelo......

Trees.

35.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Applying Compost to Citrus Trees . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Watermelon Grown in Sandy Soil With and ...Without Compost Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 ;..

Compost Application Eliminates Ashy Stem Blight :in Bush Beans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 ;

Compost Used as a Growing Medium forContainer-Grown Dwarf Oleanders.. . . . . . . . . . . . . . . . . . . . . . .44

.Compost Used as a Growing Medium forContainer-Grown West Indian Mahogany . . . . . . . . . . . . . .44

Compost Applied as a Topdressing Between Tree iRows in a Slash Pine Forest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 ;

Steps for Successful Compost Market ..Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 !...Quality Limits for Compost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 !..Classification of Compost Made from

...Solid Waste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 ;..

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Effects of Compost on Nutrients in Turfgrass . . . . . . ..46

Relationship Between Turfgrass TopdressingRates and Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 ;

6COMPOST U S E I N F L O R I D A

PART I: THE BASICS/INTRODUCTION

Beyond the BackyardCompost PileThe use of compost is proving to be an environmentally-

friendly, potentially profitable business for Florida 3cl

agricultural interests.

I n 1992, to address the problemof decreasing space in Florida’slandfills, the State of Florida

...........prohibited the disposal of grass iclippings and other yard refuse in :lined landfills. However, the ban i.also gave rise to a promising :.industry based on a natural ..process as old as life itself: i.cornposting. Compost, a mixture iconsisting largely of decayed iorganic material, occurs naturally !.every time trees shed their

...autumn leaves. As the dead leaves :decompose, they protect and !.enrich the soil underneath. Now ithis simple, natural process is ibeing transformed into a sophisti- :cated science, one that extends far ibeyond the backyard compost ;heap and that offers numerous ibenefits for Florida’s agricultural !.interests and the environment. [

Given Florida’s year-round !.growing season and porous, :

....sandy soils, the humus-likesubstance which results fromcornposting has numerouspractical applications in the state.These include field crops andvegetables, landscaping and

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horticulture, citrus groves, golf [courses, forest lands, and

.....phosphate mine reclamation. i

Florida now has 12 permitted i.cornposting facilities and dozens iof mulching facilities, which help ito recycle more than 1.3 million i

tons of urban plant debrisannually. And solid wastemanagers are targeting otherorganic materials as potentialcandidates for cornposting,

......including food, liquid, and animal iresidues. ....

William Hinkley, ct

THE BUREAU OF SOLID AND HAZARDOUS WASTE

FLORIDADEPARTMENTOF

ENVIRONMENTALPROTECTION

TALLAHASSEE$?LORIDA

JOHND.SCHERT,EXEC~TI~DIRECTOR

FLORIDACENTERFORSOLIDAND

HAZARDOUSWASTEMANAGEMENT

UNIVERMTYOF~ORIDA

GAINESVILLE,FLORIDA

This guide presents anoverview of some of the benefi-cial uses of composts in Floridaand discusses the factors thatinfluence the production, quality,and use of compost. Included arethe results of 10 scientific studiesby researchers at the Institute ofFood and Agricultural Sciences(IFAS), demonstrating howcompost can have a positiveimpact on agricultural operationsin Florida. The information isintended to help agriculturalinterests, regulatory agencies andthe general public better under-stand cornposting and the use ofcompost products, and its greatpotential in improving Florida’ssoils and environment. 0

.

WILLIAM HINKLEY JOHND. SCHERT


PART I: THE BASICS/CHAPTER 1

Compost and WasteManagement in FloridaFlorida’s growing population, year-round growing season,and large agricultural industry provide a uniqueenvironment for the development of organic recycling/composting programs.

MIT~HKESSLERANDALLI~~N S~mcy

Wfwm MANAGEMENTCONSULTANTSIN~.TIASOLIDTAMPA,FLORIDA

F lorida is the fourth mostpopulous state and one ofthe fastest-growing in the

United States. Its mild climateand year-round sunshine attracthundreds of new residents to thestate every day and over 40million tourists each year. ForFlorida’s solid waste managers,this booming population, plus theload from tourists, translates intoa growing waste stream. In 1995,Florida’s population was morethan 14 million, and the totalmunicipal solid waste (MSW)generated that same year wasclose to 23 million tons - awaste generation rate of approxi-mately 9 pounds per person perday. These figures are approxi-mately twice the national averageof about 4.3 pounds per personper day.

next decade. They continue toexpand their programs to targetnew materials and to exploreother sources for the recovery ofadditional materials. To maximizerecovery rates, solid waste profes-sionals have turned their attentionto materials which have beenrelatively neglected. These includepaper, comprising 26.3 percent ofall municipal solid waste (Figurel-l), and construction anddemolition debris, comprising22.6 percent of the waste stream.

With Florida’s warm climateand lush subtropical landscapes,urban plant debris (UPD) presentsthe most interesting potential forincreased recycling in the state.As Figure l-l indicates, UPDrepresent 14.4 percent ofFlorida’s MSW stream. In 1992,to encourage recycling of thisvaluable organic material, theFlorida Legislature passed a lawprohibiting the disposal of UPDin landfills designed to acceptmunicipal solid waste. Inresponse, the majority ofFlorida’s counties have imple-mented source-separated UPDcollection systems. Researchersestimated that by 1995 more than3.3 million tons of UPD weregenerated in Florida every year.Yet studies indicated that onlyapproximately 53 percent of theseorganics were recycled.

serve as disposal facilities for non- recovered materi .als.

In an effort to maximize therecovery of valuable materials ifrom the waste stream, in 1988, :the Florida legislature enacted the [Solid Waste Management Act i.that mandated a 30 percentrecycling goal for Florida ..counties. The impact of this ;legislative initiative has been i..impressive. In response, counties ihave implemented curbside and idrop-off recycling programs, i.encouraged recycling participa- ition within the commercial sector, iand developed a variety of urban iplant debris mulching andcornposting programs. Today,Florida has more than 300curbside recycling programs, 12 ipermitted cornposting facilities, iand numerous other mulching ifacilities. According to Florida iDepartment of Environmental iProtection (FDEP) statistics, :more than half of Florida’s 52 i

Keeping Pace With aGrowing Population

To manage this burgeoningwaste stream, Florida relies on avariety of methods, includingwaste reduction and recycling,landfilling, and combustion.Waste reduction programs aredesigned to limit the productionof waste, reducing the need tomanage it. Recycling programsrecover valuable materials fromthe waste stream so that thematerials can be reused. Landfills

counties have achieved recycling /rates of 25 percent or higher. :

...Expanding the Focus i

From 1989 to present, the /amount and percentage of .

materials recycled in Florida has !increased steadily. Despite the :success of existing recycling iprograms, Florida’s solid waste imanagers have their eyes on the :.


CHAPTER I: COMPOST AND WASTE MANAGEMENT IN FLORIDA

Office Paper 0th:; itPer. 0 Food WasteCorrugated Paper I 5.4%

White Goods0.9% TiresA An,

C & d Debris22.6%

Figure l-l: Composition of Florida’s Waste Stream (Jan. 1, 1995-Dec. 31, 1995)

Undeniably, there was room forimprovement.

That improvement began in1995, when the FDEP approvedthe deregulation of UPD com-posting, a move that cleared theway for industry expansion. Atthe same time, cornposters havebegun focusing their efforts onestablishing consistent productdefinitions, quality controlstandards, and uniform testing.If Florida’s emerging compostindustry is to flourish economi-cally, buyers of compostedorganic material need to knowexactly what they are buying andbe assured that each product’squality is consistent.

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....At the same time, researchers

have focused their attention onevaluating the composting processand exploring opportunities forexpanding its use. The commer- icial marketing of compostproducts has been encouraging. i

’Compost has found one niche inagricultural applications in the ;cattle and citrus industries.Additionally, favorable govern- !ment purchasing policies havehelped to expand markets. For

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example, the Florida Department !of Transportation has adopted ispecifications for composted imaterials and mulches made from :urban plant debris, and has ..demonstrated the cost effective- iness and superior performance of iorganic compost materials in its :Right-of-Way landscaping and :maintenance programs. In this isupportive environment, Florida :can expect to experience contin- :ued growth in urban plant debris iprocessing and cornposting. i

Anticipating Future Trends iFlorida’s growing resident i

and non-resident population, !year-round growing season, and !large agricultural industry /combine to provide a unique ienvironment for the development !of other organic recycling/ icomposting programs. In addition ito UPD, other organic materials !are gaining notice as potentially irecoverable portions of the waste istream. This renewed interest in iorganics has spawned a variety of iinnovative research and develop- :ment projects, including MSW icomposting and vermi-

composting projects.Other recent projects have

moved beyond traditional urbanplant debris processing andcomposting to target otherorganic materials, including food,liquid, and animal residuals.Florida’s organic recyclingprograms continue to expandwith the support of innovations incollection methods (especiallyco-collection of organics in splitcollection vehicles), and increasedon-site processing.

For organics recycling tooccur, compost safety standardsmust be defined, and safe, eco-nomically sound uses for compostmust be identified through coordi-nated research programs. Such amarket development researcheffort is under way through apartnership involving the FloridaDepartment of EnvironmentalProtection, the Florida Center forSolid and Hazardous WasteManagement, and the Universityof Florida’s Institute of Food andAgricultural Sciences.

Perhaps the most importantfactor influencing developmentsin Florida’s solid waste manage-ment practices is the increasingpressure to improve the efficiencyand accountability of municipalsolid waste managementprograms. Variable rate collectionprograms are expected to grow,driven by the push for greaterreduction in sources, and anincrease in return on investment.In Florida’s present economic,legislative and regulatory environ-ment, the future for recyclingorganics looks particularly bright.In sum, Florida’s compostingindustry is like a sleeping giantabout to awaken to a comingdecade of healthy growth andenergetic activity, when recyclingof organics will play an increas-ingly important role in managingFlorida’s MSW stream. 0

l()COMPOST U S E I N F L O R I D A

CHAPTER I: COMPOST AND WASTE MANAGEMENT IN FLORIDA



What is Compost?Once considered waste products, composted urban plantdebris and other organic materials have the potential tobreathe new li fe into Florida’s sandy, nutrient-poor soils.

MAJXGIE LYNN STRATTON AND JACK E. RECHCIGL

UNIWWTY OF FLORIDA/INSTITUTE OF F OOD AND

AGRICULTURAL SCIENCES

RANGE CATTLE RESEARCH AND EDUCATION CENTER

ONA, FLORIDA

C omposting is a biologicalprocess in which microor-ganisms convert organic

matter into a stabilized, humus-like substance. Many of theorganic materials used for com-posting are inappropriate in theirraw form for use on land oraround living organisms becauseof the presence of odors, weedseeds, human pathogens, andstorage and handling constraints.Cornposting helps to break downorganic residues, stabilizenutrients, destroy weed seeds, andcontrol possible toxins or diseases(Barker, 1997; Stratton et al.,1995; Hoitink and Keener, 1993;Haug, 1993). The resulting com-post has numerous horticulturaland agronomic benefits and isenvironmentally safe for use onsoils around plants, humans, andanimals (Stratton et al., 1995;Barker, 1997).

Controlled decompositionoccurs as the result of the activi-ties of naturally occurring macro-and microorganisms (Figure 2- 1).Bacteria, actinomyces, and fungiare the primary microorganismsinvolved in decomposition. Togrow and multiply, these micro-organisms require carbon as anenergy source, nitrogen to buildproteins, moisture, and oxygen.Enzymes, the active proteins, areproduced by bacteria and assist in

IZCOMPOST U S E I N F L O R I D A

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breaking down complex carbohy- idrates into simpler forms, which /bacteria can use for food. The !nutrients that become availableduring decomposition remain in !the compost within the bodies of inew microorganisms and as .humus. Not all decomposition is !microbial; in fact, it starts with :macroorganisms, including earth- /worms, grubs, millipedes, spring itails, and centipedes, which assist i.in the process by digging,

..

chewing, and mixing compostable i.materials.

...The cornposting process does i

not stop at a specific point but icontinues until the remaining inutrients are consumed by the last iremaining organisms and until imost of the carbon is converted iinto carbon dioxide and water(Rynk, 1992).

Compost has many beneficial iuses. Compost improves soil !aeration, soil drainage, the water- iholding capacity of sandy soils, /.the percentage of organic ...materials in soils, and the ability iof soils to absorb and holdnutrients.

Cornposting Past andPresent

The simplest form of corn- 1 The first recorded method ofposting - the decomposition of : cornposting community wastesplant materials where they fall - ihas been occurring naturally for i

was developed in India by SirAlbert Howard in 1925. This

millions of years. In naturalsettings, such as under forestcanopies, cornposting occurs asleaf litter decomposes intohumus. With the advent of cropcultivation and animal husbandry,the resulting plant residues andanimal manures were sometimesdecomposed by gathering theminto mounds or piles to allowcornposting to occur.

Farmers, greenhouseoperators, nursery crop managers,landscapers, orchardists, backyardand organic gardeners have beenmaking small compost heapsinformally for decades, oftensimply to save the cost oftransporting and disposing thematerials. During the past fewdecades, cornposting has becomea sophisticated and somewhatwell-researched science. Andwhile cornposting is still practicedon a backyard or small-farm scale,more and more often, it is nowcarried out on a large scale as partof local municipal waste manage-ment programs. On a municipallevel, cornposting operationsusually require sophisticatedmachinery and engineering(Stratton et al., 1995; Hoitink andKeener, 1993; Haug, 1993).

CHAPTER 2: WHAT IS COMPOST?

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method, called the Bangalore or !Indore system, simply involved ialternate layering of wastes in :trenches. Over time, as the scope i.and scale of cornposting

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increased with the amounts and itypes of waste products handled,innovative methods were devisedto speed or ease the process. Thelayers were mounded, spread,aerated with forced air, turned,enclosed, exposed, chopped,ground, dried, wet, sifted,dumped from platforms, conveyed i.up belts, or separated at the

..source, for example. For the most ipart, the various processes were :named for the company or ..inventor involved with the latest iinnovation and are summarized iin a review article by Stratton et ial. (1995).

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In the United States during a irecent 5 year period, cornposting ifacilities have increased from !2,200 to almost 3,500 .(Christopher and Asher, 1994; i

Figure 2-1: Food Web of the Compost Pile

Ken McEntree personal commu-nication). During the 14 yearsprior to 1997, biosolids com-posting facilities have increasedfrom 90 total projects nationwide(61 operating facilities) to 332total projects (262 operatingfacilities) as reported by Goldsteinand Block (1997’0). Seven statesreported a decrease in biosolidscornposting from 1996 to 1997(Goldstein and Block, 1997b).

Compost MaterialsAny number of materials, or

feedstocks, can be composted,including grass clippings andother types of urban plant debris,biosolids (commonly known assewage sludge), and otherorganic materials. Recently, therehas been an increased interest incornposting municipal, industrial,and agricultural by-products(Stratton and Rechcigl, 1998).Municipal solid waste, commonlycalled trash or garbage, has been

.; composted and applied to manyi crops, including forage pastures,.; with improved yields and otheri benefits (Shiralipour et al., 1992a;i Stratton and Rechcigl, 1997).i Coal bottom and fly ash, cement.i kiln dust, biosolids, water treat-.i ment sludges, food processingi by-products, animal and planti residues, by-products from metali smelting, paper and wood indus-i tries by-products, tannery sludges,i textiles production by-products,i rock dusts, chemical and drugi production by-products have alli been composted and land-appliedi (Stratton and Rechcigl, 1998).

Unfortunately, not everythingi that can be composted is com-i posted. Barker (1997) estimatesi that 827 million tons of com-: postable materials are producedi each year, largely by agriculture,.: municipalities, and industry.i However, only 140 million tons,i or 17 percent, of those are.i collected for cornposting.

umers

Source: Dr. Daniel Dindal, cited in Michigan Department of Natural Resources (1989). Yard Waste Composting Guide


CHAPTER 2: WHAT IS COMPOST?

.Cornposting Methods :

Currently, some of the best i.processes for cornposting

...municipal solid waste or biosolids iinclude separating the source :materials at their point of origin :(source separation), reducing the [.size of the materials (sizereduction), and carefully mixing,aerating, and curing the compostfor a few to several months toensure compost maturity and istability.

The composition and method iof processing compost varies :greatly with the feedstock icomposted (Stratton et al., 1995; [Barker, 1997). If two or more imaterials are composted together,a method known as co-composting,the cornposting process may be iaccelerated and the composition iof the final product may be

...greatly enhanced as a soil amend- i.ment and conditioner (Stratton iand Rechcigl, 1997). For example, itwo materials composted together imay include one high in carbon, :such as woody plant materials, iand one high in nitrogen, such as i

biosolids. With proper mixingand ratios, and attention toaeration, particle size, moisturecontent and other engineeringconsiderations, the resultingcarbon-to-nitrogen ratio helps tospeed and enhance the compost-ing process while also producinga high quality end product(Stratton et al., 1995; Haug, 1993;Barker, 1997). In Florida, thePalm Beach County Solid WasteAuthority’s cornposter is such afacility.

For each combination ofmaterials, compost mixes andratios of feedstocks, as well asmethodology and processes, arespecifically engineered for thematerials being composted andmay be site-specific (Haug, 1993).Much research is currentlydirected at cornposting ofpreviously disposed resources andby-products of several industries(Stratton and Rechcigl, 1998).

Compost maturity has beendetermined in a number of waysby a number of differentresearchers. In general, maturity

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refers to properties of thecompost that include, but are notlimited to

n lack of plant toxins, suchas acetic acid, phenols, andammonia

n stabilization (temporaryimmobilization) of nutrients suchas nitrate-N, phosphorus, iron orother elements which couldotherwise enrich ground orsurface waters

n the absence of detrimentalbacteria, fungi and noxious odors

n the presence of desirablemicroorganisms, and

n a noticeable reduction ofheating upon rewetting (Strattonet al., 1995).

Several quick bioassays havebeen developed to check compostmaturity. An easy method is aseed germination test on compostextract. (A. Shiralipour,University of Florida, personalcommunication). Others prefercarbon dioxide release (Graetz,1996) or oxygen uptakemeasurements. 0



Developing a Marketfor Compost ProductsThe potential market for compost products in Florida isgreat. The challenge is convincing the consumer to usecompost.

AZIZ sHIRALIPouRCENTERFOR B IOMASS PROGRAM S

UNIVERsITYOF~ORIDA

GAINESVILLE,~?LORIDA

T he growth of the compostindustry in the United Statesand Florida is being driven

by the increasing cost of land-filling waste, public support forresource conservation, andlegislative mandates for wastediversion - not by demand forcompost products. Yet if compostis to become a valuable resourceto be managed for profit, newmarkets for its use must bedeveloped.

How Much Compost CanFlorida Handle?

In 1996, about 23 milliontons of MSW were collected inFlorida (FDEP, 1997).Researchers estimate that, if theorganic fraction of this wastestream were to be biologicallydecomposed, about 5.5 milliontons of compost would begenerated. But key questionsremain. Specifically, is the marketcapacity in Florida sufficient touse the compost produced? Whatis the present market capacity forcomposted products? And howcan Florida build markets forcomposted products?

According to one study(Slivka et al., 1992), the state’sagricultural industry alone coulduse more than 20 million tons ofcompost each year. And

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statewide, as many as 42 million itons of compost could be used iannually within a 50-mile radius [of urban centers with populations iof more than 100,000. The ..researchers imposed the distance iconstraint of a 50-mile radius !based on the perceived limited ieconomic viability of shipping ifarther than 50 miles. In other iwords, the potential use forcomposted products in Florida is imore than 7.5 times the amount iof compost that could be ..produced each year. .

In 1992, the average annual :rate of compost penetration in iU.S. markets was less than 2% of iits potential uses (Slivka et al., i1992). If the rate of compost ipenetration in the Florida market ifollows the national trend, i.compost use in the state is only iabout 840,000 tons a year.Clearly, Florida has a market [development challenge, not a lack [of market. .

Developing a ViableMarket

For any type of compost to ibe marketable, regardless of i.origin, it must pass minimum :product standards for protection :of public health and the environ- iment. And commercial compost i.must consistently meet the .

requirements of end uses, whichmay vary widely. Many commu-nities are finding it necessary tomeet or exceed all the require-ments, and then put additionalefforts into marketing strategiesthat involve education and marketdevelopment.

The long-term feasibility ofcommercial cornposting dependslargely upon building a market bydemonstrating safe use and estab-lishing benefits, both practical andfinancial. Table 3-l outlines thesteps recommended for successfulcompost market development.

Establishing MarketNiches and OvercomingBarriers

New commercial cornpostersare discovering that not all com-post users are created equal. Eachrequires a specific product, andthe range of quality may varywidely. For example, high-valueend-uses, such as a growingmedium for landscape nurseries,require refined, mature, highquality composts. On the otherhand, lower-value end-uses,including use as a landfill cover orin reclamation of surface mines,can accept any class of general-use compost. Experienced com-post marketers have discoveredthat a low-quality compost will


CHAPTER 3: DEVELOPING A MARKET FOR COMPOST PRODUCTS

Table 3-1.

not be marketed successfully tohigh-value end-users, nor will alow-value end-user pay thepremium price for high qualitycompost. Yet both groups willrequire a safe and reliableproduct.

Easing Concerns OverCompost Quality

Quality is a function of the iphysical, chemical, and biological :characteristics of compost. .

Desirable physical characteristics i

...of compost include a dark color, :uniform particle size, a pleasant i.earthy odor, the absence of

....physical contaminants (such as iglass or plastics), consistency, iand moisture content of approxi- imately 50%. Desirable chemical /characteristics include balanced inutrient levels (nitrogen-phosphorus-potassium, and other ielements) and low levels of heavy imetals, PCBs, pesticides and salts. [In terms of desirable biological i.characteristics, the compost must i.

be mature, with high organic-mat-ter content, and be free ofpathogens and weed seeds.

One of the most importantsteps in improving compostquality is minimizing the presenceof hazardous materials such asheavy metals. The highest qualitycompost with the lowest levels ofpotentially harmful contaminants- particularly heavy metals andphysical contaminants - isderived from source-separatedorganic materials that were notmixed with other materials duringcollection or cornposting.Following the trend in Europe,the United States is beginning tomove away from mixed MSWand toward source-separatedorganic cornposting. (For more onquality assurance of compost, seepage 21.)

Meeting the Needs of theConsumer

As with all successfulproducts in the marketplace,compost must meet therequirements of the end-user.Three factors are of particularimportance to compost users:availability, cost, and quality.

’Compost must be consistentlyavailable for end-users when theyneed it. If they choose to haul itthemselves, it must be in an easilyaccessible location. The cost ofcompost is a composite of thecosts of the product, its trans-portation and its application.Although availability and costare important factors in thedevelopment of compost markets,it appears that quality may be thedecisive factor. It is often statedthat high-quality compost willalways find a market.

Teaching Consumers toTrust Compost

Communities with commer-cial cornposting facilities havediscovered that producing the

IGCOMPOST U S E I N F L O R I D A

CHAPTER 3: DEVELOPING A MARKET FOR COMPOST PRODUCTS

..finest product and making it iconveniently available are not ienough to entice some potential i

’consumers to try compost. Asolid educational program isnecessary in order to substantiatethe benefits of using the product.Fortunately, scientists and educa-tors at the Institute of Food andAgricultural Sciences at theUniversity of Florida (Smith and iShiralipour, 1997) have done ;much work in communities to ibuild convincing arguments that icommercial composts are safe iand can be used beneficially /

(Gallaher 1995b). First, the IFAS iteam designed a set of projects to idemonstrate the absence of pesti- i.cides in commercial composts iand is now studying the process /for biological remediation during icornposting. Additionally, the iscientists proved that they could /measure compost maturity and istability and indicate nitrogen [availability. Next, they demon- istrated low levels of compost itoxic metal contents and the low ilevels of these metals in crop iparts. Finally, they established ithat applying compost improved i

physical and chemical propertiesof soils for vegetable crops,assisted in retention of water andnutrients in turfgrass soils, andhelped establish woody ornamen-tals in landscape beds. Throughthe efforts of IFAS scientists,communities now have the educa-tional tools they need to convincepotential consumers that applyingmature compost is a beneficialand economically viablealternative to conventional soiltreatments. Q+


PART 2: REGULATORY AND QUALITY ASSURANCE ISSUES/CHAPTER 4

Regulations AffectingCompost Production and UseFederal and state regulations focus on safety of compostproducts.

R egulations affecting compostand its use address bothproduct procurement

provisions and environmentalrequirements. Procurementprovisions are aimed atencouraging markets for recycledproducts. Environmentalregulations set limits needed toclassify compost so it can be usedsafely. Both federal and stateregulations address these issues.

Federal Regulations forProduct Procurement

The EnvironmentalProtection Agency (EPA) guide-lines for procurement of compostare contained in Title 40 of theCode of Federal Regulations, Part247. Only one provision specifi-cally mentions compost -Section 247.15, which concernslandscaping products. Thisprovision includes compost“made from yard trimmings,leaves, and/or grass clippings foruse in landscaping, seeding orgrass or other plants on roadsidesand embankments, as a nutritiousmulch under trees and shrubs,and in erosion control and soilreclamation.” This section alsoincludes hydraulic mulch productscontaining recovered wood usedfor hydroseeding and as anover-spray for straw mulch in

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landscaping, erosion control, and ;soil reclamation. Title 40regulations can be accessed at the iEPA web site ath t t p : //www.epa.gov/epacfr40/ i(Environmental Protection CFR i..Pilot).

...The EPA has also developed :..

a series of fact sheets for its.....

“Buy-Recycled” program. The i.fact sheet for landscaping

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p r o d u c t s , EPA530-F-97-034, iand other information, including ia list of manufacturers, may be /.accessed at

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http://www.epa.gov/epaoswer/ i.non-hw/procure. htm.

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Federal Regulations forEnvironmentalRequirements

The two federal regulations :concerning compost are 40 CFR iPart 257 and Part 503. Section :257.3-5 contains provisions for i.the application of municipal solid [waste to land used for growing ifood-chain crops. This section i.appears to need revisions toreflect adoption of federalbiosolids regulations.

40 CFR Part 503 addressesbiosolids (also known as sewagesludge or domestic wastewaterresiduals). These regulations canbe accessed at the EPA web sitementioned above.

FRANCINEJOYAL

FLORIDADEPARTMENT OF

ENVIRONMENTALPROTECTION

TALLAHASSEE,~?LORIDA

State Requirements forProduct Procurement

Florida recognizes thatcompost is an importantcomponent of recycling. Section403.7065, Florida Statute (ES.),requires state agencies, as well asothers who use state funds, toprocure products or materialswith recycled content where theyare reasonably available. Notethat the definition of “recycledcontent” includes compostedmaterials. Further, specificprovisions for state procurementof compost are found in Section403.714, ES. This sectionspecifies that state agencies must“procure compost products whenthey can be substituted for, andcost no more than, regular soilamendment products, providedthe compost products meet allapplicable state standards,specifications, and regulations.”This provision further requires thedevelopment of uniform productspecifications for procurementand use of compost by all stateagencies. Copies of thesespecifications may be obtained bycontacting the FloridaDepartment of ManagementServices, Division of Purchasingat 4050 Esplanade Way,Tallahassee, Florida 32399-0950.


CHAPTER 4: REGULATIONS AFFECTING COMPOST PRODUCTION AND USE

State EnvironmentalRequirements

Two Department ofEnvironmental Protection (DEP)regulations specifically addresscompost use in Florida, depend-ing on the feedstock processedinto the compost product. Theseare Chapter 62-709 (Criteria forthe Production and Use ofCompost Made from SolidWaste) and Chapter 62-640(Domestic Wastewater Residuals),Florida Administrative Code(F.A.C.). Copies of these rulescan be obtained from theDepartment’s web site at:http://www.dep.state.fl.us orfrom one of the DEP DistrictOffices.

Solid wasteState regulations governing

the use of compost made fromsolid waste are found in Chapter62-709, F.A.C. The majority ofthis chapter contains requirementsfor the compost-producing facilityitself. However, this rule also con-tains a classification scheme anduse restrictions based on the typeof compost produced.

Compost made from solidwaste is classified based on thetype of waste processed, compostmaturity/stability, the presence offoreign matter, the size of holes inthe sieve used to screen the com-post, the organic matter content,and the concentration of heavymetals. The concentration codesused in the classification schemeare identified in Table 4- 1. Thevalues for “Exceptional Quality”limits specified in the federal reg-ulation are included in this tablefor comparison.

Table 4-2 illustrates the classi-fication scheme for compostedmaterials. The requirements forType Y and Type YM are identi-cal. However, a classification for“yard trash only” was mandatedby the Florida legislature.

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TABLE 4-1Quality Limits for Compost

TABLE 4-2Classification of Compost made from Solid Waste

Types of CompostMade from Solid Waste

<10mm;; organic matter >25% (fine)

* This material may not contain any foreign matter, such as glass or metal shards, ofa size and shape that can cause injury.

Compost maturity, for purposes i use by commercial, agricultural,of this regulation, is determined i institutional or governmental.by whether the compost will i operations. In other words, thereheat to more than 20 degrees .Centigrade (36 degrees

...Fahrenheit) above ambient

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temperature and the percent ..reduction in organic matter.

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Classification of a compost ..made from solid waste affectshow it can be used. Only suchcomposts classified as Y, YM or

......A have unrestricted distribution.

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.Types B and C are restricted to

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only restriction placed on Types Band C is that they cannot bedistributed for use by the generalpublic. Further, only Type B canbe used in situations, such as in apark, where contact with thegeneral public is likely. Compostclassified as Type D can only beused at landfills or land reclama-tion projects where contact withthe general public is not likely.


CHAPTER 4: REGULATIONS AFFECTING COMPOST PRODUCTION AND USE.

Finally, any solid waste compost iclassified as Type E must be !disposed of in a landfill unless it ican be demonstrated that its use :will not harm the public or the ienvironment. Most compost iproducts made from solid waste ihave been classified as Types Y, i.YM or A.

There are also restrictions :regarding the total amount of iheavy metal that can be applied to isoils. These restrictions, expressed /as pounds per acre, are cadmium i- 4.45; nickel and copper - 111; izinc - 222; and lead -- 445. As ithese values are based on the i.most restrictive soil cation .....exchange, the rule also contains a :provision that allows a user to i.demonstrate, through an analysis i.of the cation-exchange capacity iand other physical and chemical icharacteristics of the receiving isoil, that a higher application rate :would still provide an equal i.degree of protection. ....

While this section discusses :.the current requirements, the :concentrations for heavy metals iin the classification scheme were iestablished in 1989 and were :based on the criteria used to i.regulate biosolids prior to

....adoption of 40 CFR Part 503 by ithe Environmental Protection iAgency. These EPA standards i

.were also used in the DER's !Residuals Rule, Chapter 62-640, iF.A.C. Further, not only are the i.classification concentrations in !the Solid Waste Compost Rule iout-of-date, they are also based on idifferent risk assumptions and :methods of calculation than are ithe Soil Cleanup Target Levels i.used for other reuse-type ...decisions within the Division of /Waste Management. Given that iRule 62-709.600(8), F.A.C., istipulates that “compost shall not ibe used in any manner that will iendanger public health andwelfare and the environment,” !and given the need forconsistency within the Division [for approving reuse projects, it is ianticipated that rule development [will be initiated to update this irule and to incorporate the Soil iCleanup Target Levels for heavy i..metals in compost. ...

....Biosolids ....

State of Florida regulations :governing the use of biosolids are :contained in Chapter 62-640, iF.A.C. The DEP Division of iWater Facilities provided a isummary of regulations affecting iresiduals use in Biosolids

...Management in Florida: Beneficial i..Use of Domestic Wastewater

....Residuals (DEP May 1997).* i

Chapter 2 of that document“Regulations Affecting theBeneficial Use of Residuals,”addresses residuals classified as“Class A” or “Class B" underboth state and federal regulations,and residuals classified as “ClassAA” under state regulations.

In summary, only biosolidsthat have received the highestdegree of treatment for pathogenreduction and that also meet themost stringent pollutant limitsspecified in the regulation aredesignated as Class AA. Most orall of the biosolid compostcurrently produced in Floridameets the Class AA requirements.These residuals are subject to the“Exceptional Quality” limitsspecified in the federal regulationsand the Class AA limits listed inthe state rule. While use ofbiosolids meeting these criteriadoes not require an AgriculturalUse Plan, nutrient contentinformation and recommendedapplication rates must beprovided to the user.

A Matter of SafetyIt is important to remember

that the criteria established in theenvironmental regulations addressproduct safety and not therequirements of a particularend-user. 0

*Copies are available free of charge from the DEP's Bureau of Water Facilities, 2600 Blair Stone Road,Tallahassee, FL 32399.



Compost and QualityAssuranceCompost products made with an emphasis on quality andconsistency will have no shortage of uses or users.

GEORGEE.FITZPATRICK

UNIVERSTYOFFLORIDA

FORTLAIJDERDALERESEARCHANDEDUCATIONCENTER

FORTLAUDERDALEJLORIDA

C omposts are made from a ;changing assemblage of iorganic feedstocks. For this i.

reason, there can be a great deal !of variation in the chemical and [physical parameters of compost. iThe quality of the compost can :.influence the soil’s pH, soluble !salt levels, exchange capacity, :aeration, particle size distribution, ibulk density and water-holding i..capacity. Consequently, thehighest quality compost products ifrequently compare favorably with ipeat and other high value organic i.substrates. The low quality

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compost materials may retard iplant growth, and, in extreme !.cases, may contribute to plantmortality.

Plant producers should beaware that certain qualityparameters can make thedifference between successful andunsuccessful use of compostproducts.

Assessing Compost Quality i..Parameters

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Compost products are used in ifour general ways: (1) as a stand- i.alone container growing medium, !(2) as a component in a container /growing medium mixture, (3) as ian organic top dressing, and i.(4) as an incorporated soil

......amendment.

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Although there is no perfect i

growing medium for all crops ;.under all growing conditions, inumerous authors have described igeneral recommendations. For :example, for container grown ifoliage crops, Joiner (198 1) irecommends the following .general parameters: bulk density: /0.30 grams per centimeter cubed :(g/cm3) (dry), 0.60-1.20 g/cm3

.i

(wet); percent pore space: 5-30%; ipercent water-holding capacity: i20-60%; pH: 5.5-6.5; soluble isalts: 400-l ,000 ppm; cation- iexchange capacity: 1 O-l 00 imeq/ 100 cm3.

.

A variety of plant species are :.sensitive to high salt concentra- itions. Salts in the growth medium idisrupt water uptake or directly iaffect the physical functions of iplants. If these types of plants are iexposed to high salt concentra- :tions, their growth might be :suppressed or seized. Therefore, i.composts with high salt

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concentrations could cause...

toxicity in sensitive plant species. iEven a high rate of compost iapplication with low salt content [might cause injury in such plants. /Thus, a high quality compost !physically may be low quality if /the salt concentration is high. !

Of the four general uses for i.compost, the stand-alone

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container growing medium ..category requires the highest :

quality compost. When compostproducts are used as componentsin growing medium mixtures orare applied directly to agriculturalsoils, a lower quality of compostproduct may be acceptable. Forexample, Rynk et al. (1992)indicate that a soluble saltconcentration of less than 2.5decisiemen per meter (dS/m) isnecessary for a stand-alonecontainer medium, but a value ofless than 6.0 (dS/m is acceptablewhen the compost product is tobe used as a component in agrowing medium mixture, and avalue of less than 20 dS/m isacceptable when the compostproduct is to be used as anincorporated soil amendment. Ifsalt levels are a concern, it is wiseto wait until a rain or otherwatering event occurs to dilutethe salts.

Numerous factors caninfluence the likelihood that anycompost product will havesufficient quality as a rootingmedium. These include the parentmaterial from which the compostproduct was made, the pre-processing and postprocessingprocedures to which the substratewas subjected, the amount oftime of active cornposting and thematurity of the compost product,the amount of inert material inthe compost product, the


CHAPTER 5: COMPOST AND QUALITY ASSURANCE

concentration of regulatedelements (heavy metals), andthe presence of pathologicalmicrobiological organisms. .

Parent Material .The composition of the !

parent material can sometimes [influence the quality of the ..compost product. The parent /material may affect the particle isize, nutrient content and soluble isalts in the final product. Very ifine composts tend to separate i.and block drainage in pots, while :a compost with coarse, fibrous iproperties creates a porous medi- iurn that facilitates drainage. For /example, a compost made from ibiosolids (sewage sludge) supports :.more rapid growth in container- igrown viburnum (Viburnum /suspensum) than do composts :made from nitrogen-poormaterials such as garbage, urban i.plant debris, and stable sweepings(Fitzpatrick and Verkade, 199 1).

Preprocessing andPostprocessing

Procedures employed at thecornposting facility before and iafter the active cornposting period :can sometimes influence compost iquality. For example, sludges ifrequently are stabilized and iconditioned prior to cornposting. iIf a sludge is stabilized by treat- iment with ferric chloride and :lime, a common practice in many i.wastewater treatment facilities, ithe level of soluble salts in the ifinished compost product may be :significantly higher than incompost made from sludge that [had been stabilized using a wet- i.air oxidation process. When corn- iposts made from sludges treated i.with stabilization and ......conditioning preprocessing

..procedures were used to grow the !non-salt-tolerant container crops iSpathiphyllum ‘Mauna Loa' and iSchefflera arboricola, plants grown i.

in the compost with higher solu- ible salt levels were significantly i.smaller than plants grown in

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composts with lower soluble salts(Figure 5-l). However, both

40% peat, 50% pine bark and 10%sand (Fitzpatrick, 1986).

....Other processing procedures, i

such as screening, can influence !the physical quality of the corn- ipost products by making themmore homogenous and, conse-quently, easier for the grower tomix and apply. Smaller plantsusually require composts thathave passed through small diame-ter screens. Plants grown in largetubs or in soil with incorporatedcomposts may do well with

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coarser material.

Active Cornposting Timeand Compost Product

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Maturity .

The earliest references on !cornposting time published in the /modern era (e.g., Howard and iWad, 193 1) indicate an optimum ‘i..cornposting time of approxi- ....mately 6 months for mixtures !containing 25% of high nitrogen !.material, such as animal manure, iand 75% of high carbon material, i.such as plant debris. Many ....current commercial compostproducers promise a stabilizedend product in a much shorterperiod because of the capabilityfor preprocessing, mixing,aerating and managing moisture [content. Producers may feel a istrong economic incentive to i.accelerate active cornposting into [the shortest possible time period. :If the processing time is too short, i.an immature compost may result. iCommercial plant producers who ipurchase compost products from isuch sources must be mindful of :the negative effects associated

Figure 5-1: Spathiphyllum ‘Mauna Loa'grown in a compost product that had anaverage electrical conductivity of 3.9dS/m (left) attained an average size of1.39 times the control. Plants grown incompost with 7.5 dS/m conductivity(middle) attained an average size of 1.19times the control. Control mediumconductivity averages 3.5 dS/m(Fitzpatrick, I 986).

with immature composts. Theseinclude biological blockage ofnitrogen uptake (nitrogen-rob),deformity or death of plant partsby phytotoxic chemicals in imma-ture composts, increased mobilityof certain toxic elements in thesoil, and similar effects (Jimenezand Garcia, 1989). Many growerswho use compost products storenewly delivered material for 6-12months, allowing it to decomposefurther, as insurance againstpossible phytotoxic effects.

Inert Material ContentCertain types of parent

materials are often likely tocontain noncompostable sub-stances, such as particles of glass,plastic, and metal objects. Thesematerials may be unsightly andhazardous, particularly if theinert materials have sharp edges.If a compost is made exclusivelyfrom materials such as yard trim-mings, leaves, or other plantdebris, inert material usually isnot a problem. If, however, acompost is made from municipalsolid waste, inert materials mightcause problems, particularly if theparent materials had not beensubjected to sufficient preprocess-ing to segregate inert materials.Some states have passed environ-mental regulations limiting the


CHAPTER 5: COMPOST AND QUALITY ASSURANCE

amount of inert materials allowed iin compost products. In Florida, :state regulations mandate that iinert materials may not exceed i2%, by weight, in compost prod- iucts marketed for unrestricted ihorticultural uses. In other areas, i.compost producers and brokers ihave developed self-regulation iprograms. For example, compost !producers in Ohio will not sell a icompost product for nursery use iif the inert material level exceeds ;OS%, by weight (Tyler, 1993). i

;Regulated Elements i

One of the almost universal iconcerns related to compost use is :the question of regulated ele- iments. The U.S. Environmental :Protection Agency has issuedrecommendations for themaximum permissible levels of :10 heavy metals in compost iproducts: arsenic, cadmium, !.chromium, copper, lead, mercury, imolybdenum, nickel, selenium iand zinc. Many states have passed itheir own regulations, using the ifederal recommendations as iguidelines. While there can be i.substantial differences in heavy !metal concentrations between idifferent types of compost !products that may be attributable ito the parent material and the irelative level of preprocessing, ;the overwhelming majority of icompost products available at the :present time fall well within ifederal and state guidelines i.(Chaney and Ryan, 1993). In fact, icommercial composts in Florida iare required to meet these guide- ;lines.

....The safety of compost i

products is further assured by the ’reduction of toxic heavy metals inwaste streams brought about bythe implementation of industrialpretreatment programs, as well asby quality control programs

practiced by commercial compostproducers and monitored bygovernmental regulatoryauthorities.

Biological StatusA common concern held by

many people relative to compostuse is the possible presence ofpathogenic organisms. The hightemperatures reached duringactive cornposting (from 130 to140 degrees Fahrenheit) havebeen shown to reduce to insignifi-cant levels any pathogens thatmight have been present in theparent material (Burge, 1983;Haug, 1993). However, sincecommercial cornposting isfrequently conducted on a largescale, involving hundreds of tonsper day, questions have beenraised about whether cool spotsexist in places within active com-post piles and whether pathogenicorganisms could reinoculate thefinal product. These issues arenormally addressed by examiningrepresentative samples ofcompost products and conductingmicrobiological screenings.Usually, the pathogens themselvesare not cultured. Rather, thecompost samples are tested forthe presence of indicatororganisms, such as fecal coliformbacteria. Indicator organism testsare simple, reliable and arerequired by both federal and stateregulations. They serve as anadditional safeguard to insure themaintenance of compost quality Iand safety.

Another microbiological issueof concern is the presence of theubiquitous thermo-tolerant fungusAspergillus fumigatus, a saprophytefrequently found in decayingorganic materials. A. fumigatus isone of the relatively few fungithat can be pathogenic tohumans, since the human body

temperature, 37 degrees C, is theoptimum temperature for itsgrowth (Oliver, 1994). However,the relatively small number ofconfirmed cases of aspergillosis,coupled with the ubiquity of A.fumigatus in the environment,implies that the susceptibility ofhumans is rather low. A recentreview of the literature indicatesthat humans with suppressedimmune systems may become illafter only minimal exposure to A.fumigatus. But healthy individualsfrom the general populationappear to show no significanthealth impacts from exposure tothis fungus (Maritato et al., 1992).Moreover, the average horticul-tural worker is exposed to manysubstrates containing A. fumigatus,such as soil, peat, sawdust, woodchips, and other products. Ifhorticultural workers do notexperience any aspergillosissymptoms from contact withthese kinds of products, it is notany more likely that they wouldexperience symptoms as a resultfrom exposure to compostproducts.

Weed seeds are also aconcern. Shiralipour (1990) andMcConnell placed weed seeds inplastic mesh bags, which werethen placed in cornposting piles.Exposure of the weed seeds totemperatures of 150 degreesFahrenheit for only a few hourswas adequate to kill the weeds.

Growing Possibilities forQuality Compost

The potential for usingcompost by agricultural interestsis great. If compost products aremade with an emphasis onquality and consistency, it is likelythat use of these materials willcontinue to expand in cropproduction. 0



How to Produce HighQuality CompostThe right mix of raw materials combined with state-of-the-art technology yields a high quality end product.

PATRICK D. BYERS

SOLID W a AUTHORITY OF PALM BEACH COUNTY

WESTPALMBEACHJLORIDA

A compost recipe usually is a icombination of organic :materials, or feedstocks, /

capable of producing a balanced iend product, one that is nontoxic ito plants, people, and animals and i.that improves soil quality.

...Common fodder for cornposting iincludes tree bark, manure, leaves, icardboard, food waste, soiled ipaper, wastewater residuals :(biosolids), grass clippings, tree itrimmings - in effect, just about !anything organic and biodegrad- !able in nature. A balanced recipe !.must also factor in such parame- iters as proper moisture levels, :carbon-to-nitrogen ratio, particle /size, and porosity of the final imix.

..:Sometimes, it is necessary to i

analyze the physical and chemical icharacteristics of individual ...organic sources to help develop irecipes. Certain organic materials, !for instance, may contain contam- i.ination from sources such as ..heavy metals, pesticides, plastics, ior salts. Care must be taken to ilimit the contamination of raw i.materials.

After the raw materials havebeen selected, they must be i.combined prior to cornposting. !Mixing can be done in special iunits designed for this purpose or iby front end bucket loaders that ipick up and toss materials into a i.

homogenous mix. Many combi- i.nations can be tried and mixes ican be changed often, based on [the availability and uniformity of ithe raw materials and the needs of ’the market.

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Common CornpostingSystems

Cornposting technology canbe as simple as using a pitchforkand people power, or as sophisti-cated as computer-controlled,state-of-the-art machines willallow. Generally speaking, thebetter the technology that is used,the higher is the quality of thecompost. Three types of composttechnologies currently are themost widely used:

Windrow composting, the leastsophisticated of the three,involves placing a mixture oforganic waste materials into long,narrow piles approximately sixfeet high by twelve feet wide andas long as is necessary. Thecompost process is accelerated byfrequent turning of the windrowwith a front-end loader or customdesigned machinery built for thispurpose. Turning fluffs the pileand increases porosity of themixture, which helps to improvethe introduction of ambient airinto the windrow.

Aerated static pile compostingprovides for mechanical

introduction of ambient air andrequires no turning of the organicmixture once the pile is formed.By controlling air mechanically,this process allows the use oflarger piles. When cornpostingwith this method, an air plenumis constructed and the organicmixture is placed in piles on topof the air plenum. Piles are builtas high as equipment allows,normally eight to twelve feet.Air is either pushed into or pulledfrom the pile by a blowerconnected to the air plenumsystem. Aerated static piles can beconstructed individually or inextended piles. Individual piles,constructed all at once, allow theprocessing to occur in batches.Extended piles consist of a seriesof cells created over the course ofmany days and stacked againsteach other to form one longrectangular pile. A temperaturesensor placed within the pileworks in conjunction with theblower to control temperature andoxygen concentrations within thepile.

In-vessel composting involvesconfining the compost process toa variety of containers or vessels.Different in-vessel systems use avariety of methods to enhanceand accelerate the compostprocess. However, each systemusually includes some method for


CHAPTER 6: HOW TO PRODUCE HIGH QUALITY COMPOST

aeration, mixing, compost processtemperature control, and contain-ment of odors. In-vessel systemsgenerally are the most costly ofthe three major technologiesbecause of high capital construc-tion costs. Most are proprietarysystems that require greateroperation and maintenanceexpenses and a higher skill levelto operate.

Once a recipe has beenestablished, the mixture will beincorporated into the composttechnology chosen, eitherwindrow, aerated static pile, orin-vessel cornposting. Thesetechnologies were designed toaccelerate the decompositionprocess of organic materials. Howthese processes are managed willeither speed up or slow down thedecomposition process, ultimatelyinfluencing the quality and cost ofthe product.

DigestionDuring the cornposting

process, microorganisms occur-ring naturally in organic materialstransform them into compostthrough digestion. That is, themicroorganisms break down thevarious organic materials intosimple compounds that are moreuniform and biologically lessactive. In order to accelerate thecornposting process, theseorganisms need an environmentthat allows them to flourish.

The main aspects for propermanagement in the cornpostingprocess include temperature,aeration, and moisture control.Low temperatures are indicativeof reduced microorganismactivity and could indicate a lackof oxygen or inadequate moistureconditions. Most often, lowtemperatures are the result of lackof oxygen.

Once the cornposting processis believed to be complete, testingshould be performed to ensurethat the cornposting goals have

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been met and the desired compostproduced. Common test methodsmeasure the carbon-to-nitrogenratio, respiration rate, moisture,pH, and weed seeds. Additionaltests are run based on regulatory,environmental, or end-userequirements.

CuringThe curing process further

assures that a uniform and well-digested compost is produced.The length of the curing perioddepends on how well the organicmaterials were decomposedduring the digestion process andon the ultimate end-use of thecompost.

During the curing period, thecompost continues to decomposebut at a slower rate than thatwhich occurs during digestion.This continued decompositionimproves the compost characteris-tics and is an important part ofthe overall cornposting processquality control program.

Maintaining aerobic condi-tions in curing piles is usuallydifficult to achieve. Anaerobicconditions can develop whichmay lead to odors and thedevelopment of compounds thatcould be detrimental to plants. Ifcompost is to be distributed fromcuring piles, it should be turnedtwo to three times to releaseodors and reintroduce aerobicconditions prior to distribution.

Curing can occur outside orunder-cover. Under-coveroperations usually have fewerproblems because rainfall doesnot factor into the curing process.When curing outside, considera-tion should be given to the effectsof rainfall, which can be eitherbeneficial or detrimental,depending on the moisturecontent of the compost. Gooddrainage, a solid base forequipment operations, and largeblock curing stockpiles willmaintain compost quality. (For

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more on block stockpiling, seepage 26.)

FinishingFinishing, or post-processing,

is usually undertaken to provide auniform and customized productthat is acceptable and marketableto customers. Considerationsinclude particle size, moisturecontent, carbon-to-nitrogen ratio,color, texture, removal of contam-inants, and nutrient and bacterialcontent. Finishing can includescreening, blending, introducingadditional nutrients and bacteria,drying, and bagging.

The most common finishingpractice is screening, which cansignificantly improve the valueand quality of compost to be dis-tributed. Screening can improvethe appearance, texture, nutrientcontent, and carbon-to-nitrogenratio of the compost, as well asremove unwanted materials.Screening also creates fractionsfor specific end uses.

The economics of finishingalso should be considered. Thecosts of finishing should beevaluated along with the valueand demand for the product.

StorageMaintaining some inventory

of finished compost products isusually inevitable. Storage ofcompost materials may also beaccomplished throughout thecuring, finishing, and distributionprocesses.

Storage of materials can beunder-cover, in containers, oroutside. Under-cover andcontainer storage will helpprevent the effect of weatherconditions on materials.Container storage will also allowthe potential for control of odors,if necessary. Outside storageusually is the least costly but canbe the most problematic. Outsidestorage considerations include thetype of storage pad, stormwater


CHAPTER 6: HOW TO PRODUCE HIGH QUALITY COMPOST

drainage and collection, odor i use of block stockpiling. Blockpotential, and Mother Nature. An iimproved area that manages

..stormwater to reduce the effects ion the materials is essential.

....Movement of materials when the iwind direction is away fromhomes, businesses, or other ireceptors is important.

Sizing of stockpiles to !prevent weather conditions from iaffecting materials includes the i

i materials, higher heat levels arealso maintained within thestorage pile to prevent thereintroduction of weed seeds andhuman disease-causing bacteria.

stockpiling is the process of....

making piles as high as possible iwithout running equipment up on _the sides of stockpiles, and as :long and wide as possible, taking :into consideration fire prevention ineeds. Block stockpiling reduces [the surface exposure of materials ito outside weather conditions. :.Because of the insulatingcharacteristics of compost ..

Typically, the heat generatedfrom the cornposting process willalso prevent rainfall fromaffecting the compost. Mostmoisture that falls on the blockstockpile will evaporate within afew days. (I)


PART 3: AGRICULTURAL USES FOR COMPOST IN FLORIDA/CHAPTER 7

The Effects of Composton SoilWhen used as a soil amendment, compost can improve soilquality, help conserve watev, and may reduce the need forfertilizers and pesticides.

AZIZ sH.IRALIPouRCENTERFOR BIOMASS PROGRAMS

thIWRZI-YOF~ORIDA

GAINESVILLE,FLORIDA

W hen used in sufficient :.amounts, compost has ;both an immediate and i.

long-term positive impact on soil :properties. Compost products :provide a more stabilized form of /organic matter than raw wastes !and can improve such physical iproperties as water-holding icapacity, water infiltration, water /content, aeration and permeabili- ;ty, soil aggregation and rooting !.depth. Compost products alsodecrease soil crusting, bulkdensity, runoff, and erosion. The ichemical properties of soils that :have been treated with compost iare often improved, as well, as are i.soil biological activities. .

Water-Holding Capacity :The application of compost :.

products can markedly increase ithe water-holding capacity of !soils. The increase is attributed to iimproved pore size distribution i(Pagliai et al., 1981). Pores in the irange of OS-50 micromillimeters i(mm), called storage pores, hold iwater necessary for growth of iplants and microorganisms. i

Most mineral soils used for :an agricultural purpose should ireceive compost rates of 10 to 15 i.tons/acre to increase water- iholding capacity by five to 10 ipercent. When 146 tons/acre of :MSW compost was applied, the i

water-holding capacity increasedby 43 percent (McConnell et al.,1993). In Gallaher’s usage ofcompost in a corn crop, thecompost treatment increased soilwater storage by an amountequivalent to two acre-inches ofrainfall or irrigation (Gallaherand McSorley, 1994).

In sandy soils of Florida withlow water retention, both thefrequency of irrigation inagricultural farms and energyconsumption resulting from waterpumping should decrease as aresult of compost application.

Soil Bulk DensityThe use of heavy equipment

for crop planting and harvestingincreases soil bulk density ofagricultural soils due tocompaction. This causeslimitation of pore spaces, whichdecreases the aeration and water-holding capacity of soils. Theincorporation of compostproducts in compacted soils, onthe other hand, decreases bulkdensity and increases porevolume, the rate of waterinfiltration and the volume of airin the soil medium (McConnell etal., 1993). The reduction in bulkdensity of mineral soils dependson the rates of compostapplication, the soil type, andthe degree of soil compaction.

Soil ErosionCompost plays an important

role in control of erosion by bothwater and wind. The degree ofsoil erosion by water depends onthe strength of soil aggregates towithstand raindrop impact andsurface flow. Composts with highorganic matter content performwell for controlling erosion bywater.

For controlling wind erosion,long-term research has shownthat use of normal-size MSWcompost is more effective than thevery fine variety’ Small particlesize and lightweight compostproducts are susceptible to winderosion under arid conditions.

Soil pHSoil pH affects the availability

and absorption of nutrients byplants, particularly micronutri-ents. Most compost products havea near neutral or slightly alkalinepH with a high buffering capacity.Elevation of pH by compostapplication can bring about strongabsorption of and, in some cases,precipitation of cadmium (Cd),manganese (Mn), lead (Pb), andzinc (Zn) in soil particles, result-ing in lower accumulations ofthese elements in plant tissues.

Most agronomic crops growwell when the soil pH is between6.0 and 7.0. Addition of compost


CHAPTER 7: THE EFFECTS OF COMPOST ON SOIL

to acid soils and subsequent pHelevation reduces or eliminatesaluminum (Al) or manganese(Mn) toxicity, which can occurwhen soil pH is below 5.5.(Hernando et al., 1989).

The change in pH values ofmineral soils by compost applica-tion depends upon the compostedmaterial and the initial soil pHpHand the soil’s buffering capacity.Incorporation of compost at ratesof 10 to 20 tons/acre usuallyincreases pH by 0.5 to 1 .O pHunit in acid soils (Hernando et al.,1989).

Cation-Exchange CapacityCation-exchange capacity

(CEC) is the sum total exchange-able cations that soil can absorb.Cation-exchange capacity of soilsis important in retaining nutrientsagainst leaching by irrigationwater or rainfall. Sandy soils tendto show the greatest increase inCEC by compost application. In aFlorida sandy soil, a compostapplication rate of 15 tons/acreincreased CEC by about 10%(Hortenstine and Rothwell, 1973).High rates of compost application(more than 10 tons/acre)increased soil CEC, while lowrates (less than 10 tons/acre) didnot change or had minimal effecton CEC. Research results indicatethat application rates of 15 to 30tons/ acre would increase theCEC of most mineral soils usedfor agricultural purposes by aminimum of 10% (McConnell etal., 1993).

Nutrient ContentAlthough compost products

contain a considerable quantity ofmacro and microelements, thenutrient content of compost prod-ucts is lower than commonly usedchemical fertilizers. And althoughnitrogen (N) and phosphorus (P)contents of compost are higherthan most agricultural soils, theavailabilities of these nutrients are


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low. One reason is that release ofnitrogen from an organic sourcesuch as compost is in a mineralform that is unavailable to plantroots. Compost nitrogen is avaluable slow released nitrogensource. The rate of microbialmineralization and release ofavailable nitrogen from structuralforms in the compost depend onthe local climate and the soil type.The first year rate may vary from5% to more than 75% (Sommersand Giordano, 1984).

Because of the warm andhumid climate and sandy soils inFlorida, the rate of nitrogenmineralization is very high; there-fore, plant response to compostnitrogen is much quicker than incold regions of the U.S., such asthe northeast, with lower annualrainfall and heavier soils.

Incorporation of composttypes with high carbon-to-nitrogen ratios will elevate thecarbon-to-nitrogen ratios of soils.A soil carbon-to-nitrogen ratioabove 30 causes nitrogenimmobilization, or nitrogen-rob,and nitrogen deficiency in plants.Nitrogen-rob occurs when micro-organisms consume the availableplant nitrogen in the soil in orderto decompose the compost.Application of nitrogen as amineral fertilizer usually correctsthis type of nitrogen deficiency.Alternatively, if cropping can bedelayed a few months, thecompost will stabilize in the soil,correcting the problem.

Application of compost as asoil amendment reduces nitrogenleaching from soil. Therefore,utilization of compost as a soilamendment could reduce theamount of commercial nitrogenfertilizer applied and decrease thepossibility of nitrate groundwatercontamination (Shiralipour et al.,1992b).

The nitrogen content of acomposted product depends onthe feedstock and processing

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technology used to produce thecompost. The nitrogen-phosphorous-potassium (N-P-K)ratio of most composted MSW issuch that application to soils at arate selected to satisfy thenitrogen needs of a crop mightresult in excess additions ofphosphorus and insufficient levelsof potassium. Consequently, theuse of supplemental fertilizersmay be required to bring thenutrient levels in balance withcrop demand. As with all fertil-ization practices, the amounts ofnitrogen, phosphorus andpotassium required for cropproduction are best determinedby soil testing.

The quantity of other macroand microelements in compostproducts depends on the feed-stock’s type and origin and themethod of compost production.Their availability is alsocontrolled by mineralization orcompost decomposition rate.Nevertheless, keep in mind thatcomposts are seldom used asfertilizer but as an overall soilconditioner.

Soil MicroorganismsThe activity of soil micro-

organisms is affected by compostapplication. Microorganisms playan important role in decomposi-tion of soil organic matter, whichleads to formation of humus andavailable plant nutrients. An in-crease in soil organic matter con-tent through compost applicationcan promote root activity, as spe-cific fungi function symbioticallywith roots, assisting them in theextraction of nutrients from soils.

EarthwormsThe population of earth-

worms is also increased by theaddition of sufficient levels ofcompost products. The soilmovements and tunneling by theearthworms results in enhancedaeration and water infiltration.

CHAPTER 7: THE EFFECTS OF COMPOST ON SOIL

.Soil-Borne Plant Pathogens

Application of compost hasbeen advocated by “organic”farmers for many years as a wayto reduce or eliminate the use ofpesticides and soil fumigants.Indeed, suppression of soil-borne iplant pathogens by organics has :been well documented by some iinvestigators (Hoitink et al., i1993). This occurs through a /

phenomenon known asantagonism or amensalism.Microorganisms that producesubstances toxic to competingpopulations will naturally have acompetitive advantage. Forexample, a species of bacteria [commonly found in compost [produces antifungal volatiles :(Fiddaman and Rossal, 1993). iHoitink et al. (1993) have shown !

that wood waste compost was atleast as effective as fungicides incontrolling Phytophthora root rots.In such cases, it appears thatcomposts increase host vigor andtheir ability to resist infection bypathogens. Thus, compostapplication can eliminate orreduce the use of pesticides. 0



The Benefits of MSWComposts in South FloridaCompost use offers an economical way to enrich thenutrient-poor soils of South Florida.

S outh Florida has a combina-tion of geographical andenvironmental conditions

that make it unique to the conti-nental United States. BecauseSouth Florida is situated on aformerly submerged coral shelf, .

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...........there is very little naturallyoccurring topsoil. In addition, theregion’s subtropical environmentensures a constant, rapid, andcontinuous degradation of anynaturally occurring organicsWith the exception of theEverglades agricultural region,this has prevented an accumula-tion of rich soils preferred byagricultural producers. However,plenty of warmth, sunlight, andwater help compensate for thelack of rich soils. Through theaddition of relatively largeamounts of fertilizers, pesticides,fungicides, and herbicides, bounti-ful good quality crops, includingvegetables, tree crops, ornamen-tals, turf, and landscape materials,can be grown successfully.Researchers are now discoveringthat the addition of composts,especially municipal solid wastecomposts, can be particularlybeneficial in this region.

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Using MSW Compost inSouth Florida

During the 1992-1993 crop iyear, approximately 20,000 tons /

of Second Nature MSW compost, iproduced by Reuter Recycling of iFlorida, was distributed over 315 i.acres of South Florida farmlands [distributed from Florida City to iBoca Raton. Two different icompost rates (20 and 40 tons per iacre, plus a control rate of 0 tons) :were applied at four different ilocations, with diverse soil types, i.ranging from sandy to rocky, that /produced a variety of crops, /including beans, eggplant, pep- ipers, tomatoes, squash, zucchini, iherbs, and others. In the compost itest areas, average crop yield :increases of between 28% and i.44% were experienced in con- !.trolled, large-scale research plots [in the fields. Results alsodemonstrated increased nutrients, !decreased crop water require- !.ments, nematode and pathogen isuppression, a reduction of the i.impact of crop production on igroundwater supplies, and a :reduction in weed populations in icompost-amended areas. There iwere also indications of possible ipest suppression in compost- itreated areas.

...While the crop responses to i.

the compost applications were icrop-specific, a general trend itoward larger plants was observed ifor most crops. There were also icarry-over crop benefits seen

....during the following season, with /

DEANRICHARDSONREUTERRE~YCLINGOFFLORIDA

PEMBROICEPINESJLORIDATROPICAL TREESCAPES

h&AMI,fiORIDA

indications of further carry-overthrough to the third season.Further, the reduction in chemicaldependency for crop productionwill favorably impact both thefarmer and the environment inthe near future. All of theseobservations are consistent withresults recorded throughout thehistory of compost production, ofthe benefits of amending nativesoils with composts.

South Florida is also home toone of the largest ornamentalplant production areas in theUnited States. Tremendousamounts of potting soils andtopsoils used in landscaping andcontainer plant production areconsumed in South Florida eachyear. One of the basic compo-nents of potting soils is peatmoss. The major topsoilcomponent used for landscapingis muck, a highly degraded formof naturally occurring sedge peatfound in limited areas of Florida.The normal function of thismaterial in nature is as a naturalwater filtration medium thatcleanses surface water as itpercolates through the groundinto the underground aquifersthat make up our groundwater.Removal of this sedge peat ormuck surface substrate for usageas a potting media or topsoileffectively removes a like amount


of natural water purificationcapability, thus reducing the water iquality as well as the amount of iclean water available for public iconsumption. Finding a suitable isubstitute for the muck and sedge ipeat fractions of potting medias !.and topsoils is a critical task. It is ibecoming increasingly clear that :MSW composts appear to have

CHAPTER 8: THE BENEFITS OF MSW COMPOSTS IN SOUTH FLORIDA

..the ability to act as that substitute.Research ongoing at theUniversity of Florida has clearlydemonstrated the ability of MSWcompost to replace peat mossone-for-one in potting soils.Demonstration projects at anumber of different commercialnurseries verified the studyresults. Landscape topsoil

production using MSW compostsas one of the major components

i proved to be a successfuli commercial endeavor, with thei end product having already beeni successfully used on numerous

landscape projects. Projecti expansions into turf production; and public works are also

planned. 0

,



How Compost BenefitsCitrus CropsApplying compost to Florida citrus trees may reduce disease,stimulate treegrowth and increase crop yield.

C itrus is the most economi- ically important and widely iplanted crop in Florida, i.

covering about 675,000 acres in iCentral and South Florida. iBetween 1992 and 1994, more !.than 10.3 million new trees were iplanted on sandy soils, mostly ilow in organic matter, and poor [in nutrient exchange and water- iholding capacity. Recent studies ihave demonstrated that compost- /.ed municipal solid waste(CSMW) and composted urban iplant debris (CUPD) may be !beneficial to citrus by reducing /the incidence of root infection, istimulating growth of young [trees, and increasing yield and i.fruit size in Central Florida citrus igroves.

The center of the citrusindustry is within a 100-mileradius of a densely populatedarea of the state, where morethan 7 million people produce 5 ikg of solid waste per person per iday, one that holds the potential ifor providing the citrus industry i..with low-cost compost. ...

Potential Uses of Compost /..in Citrus Groves

....In citrus nurseries and groves, :

Phytophthora nicotianae Breda de

populations of P. nicotianae exceed i.a threshold of 10 to 15 propagules iper cm3 of soil.

...When fungicides are used, /

they usually are applied to the soil ithrough the irrigation system two /to three times over severalseasons. However, soil-applied ipesticides are prone to loss of iefficacy after prolonged use and, /since they are water soluble, have ithe potential to leach into the igroundwater after excessive iirrigation or rainfall (Kookna et ial., 1995). Fungal resistance to /the metalaxyl has been found in iFlorida nurseries, raising concerns :about the long-term usage of this i.

Haan (synonym = P. parasitica : fungicide in citrus grovesDastur) is often an endemic root i (Timmer et al., 1998).pathogen that causes girdling of i An alternative strategy to

the trunk as a result of bark iinfection, and slow decline in /canopy vigor and fruit production /as a result of rotting of fibrous [roots (Graham and Timmer,1992). Applications of fungicides i.control fungal infection of bark /and roots and increase fibrous iroot density (Timmer et al., .1989). Although fungicides sup- ipress the pathogens, which leads ;to increased yields and fruit size iof orange and grapefruit trees on iPhytophthora-susceptible root- !stocks, yield response is often :variable. Therefore, fungicides are :not recommended unless .

J. H. GRAHAM

UNIWR!3ITYOF~ORIDA

CITRUSRESEARCHANDEDUCATIONCENTER

LAKElkFRED,nORIDA

fungicides for sustained control ofsoil-borne diseases is to periodi-cally apply composted organicmaterials as amendments tosuppress fungal root pathogens.Composted bark, when incorpo-rated into potting media, sup-presses soil-borne diseases ofornamental plants (Hoitink andGrebus, 1994). In Australianavocado groves, root rot causedby P. cinnamomi has been effec-tively controlled by intensivemulching with organic amend-ments and applications of gyp-sum (Broadbent and Baker, 1974).

In our studies of citrus,composted waste from differentsources reduced the incidence ofroot infection of citrus seedlingsthrough direct suppression of P..nicotianae in soil (Widmer et al.,1998a). We conducted green-house and field studies toexamine the potential for compostto suppress P. nicotianae andimprove root health.

Responses of Young Treesto Composted MunicipalWaste

Three trials from 1991 to1996 demonstrated that mulchtreatments of compost are highlyeffective for growth stimulation ofyoung citrus trees in newlyestablished groves (Widmer et al.,1996,1998b). Responses were seen


CHAPTER 9: HOW COMPOST BENEFITS CITRUS CROPS

for soils typical of both the ridge :.and flatwoods production areas. i

While greenhouse bioassays :predicted that compost might /suppress the pathogen (Widmer et ial., 1998a), populations of P. inicotianae were either not affected /or even increased by compost. :Despite pathogen activity in :compost-amended soils, the trees [performed nearly as well as those :in noninfested soils and signifi- icantly better than those innonamended soils. Stem diameter :and root mass of young trees !increased 20-30% in response to ipost-plant treatments with surface :.mulches as well as incorporation itreatments at planting. The

....growth response is best explained iby increased tolerance to the idisease rather than pathogen !.suppression. Tolerance is

.....attributed to improvement of /conditions in the root zone for :more efficient water and nutrient [uptake. .

Operationally, the CMSW :and CUPD is most effectively and :efficiently applied with a New iHolland 3000 side-discharge /spreader as a 5- to 10-cm thick ;mulch layer within the tree row to icover about 80% of the root isystem. Although the application irates are quite high, ranging from i150-170 metric tons per hectare, !the mulch lasts up to 2 years ibefore reapplication is necessary. !Reduction of mulch layers to 2-5 /.cm thick decreased the tree ....response and mav reauire vearly ire-application to be effective.Current trials are designed toestablish the optimum rate ofCMSW and CUPD and themechanism for the growthenhancement of young citrus in

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low organic matter sandy soils.Young trees received

adequate fertilizer and scheduled i.irrigation so compost did not isubstantially increase their

...nutrient status. Soil water-holding icapacity was elevated at the

interface between the mulch and i.the mineral soil, as was soil

..temperature. The proposed major ibenefit of CMSW and CUPD, i.increased soil water availability to itree roots, will be further substan- [tiated by measures of soil and :plant water relations. ..Responses of BearingTrees to Compost

Composted municipal waste iapplied as 5- to IO-cm thick imulch layers increased the yield i.and fruit size of Marsh grapefruit :and fruit size of Valencia orange itwo and three years after applica- ition (Widmer et al., 1997). The iresponses occurred in groves with imarginal soils and ill-adapted irootstocks that were predisposed ito damaging populations of P. :nicotianae. The effect of compost ion root density was site-specific. iCompost increased root density of [.the Valencia sweet orange trees :on Carrizo citrange rootstock in a ihigh pH, limestone-rich soil. iHowever, compost decreased root idensity of the Marsh grapefruit i.trees on sour orange rootstock in ia low organic matter sand soil i(depressional sand soak). The i.roots in the organic mulch layer iwere usually lighter in color and :healthier in appearance than :those in the mineral soil below. iThe mulch layer provided a zone iof favorable conditions for growth iand function of fibrous roots. [

The increase in yield of trees :.in very sandy, slightly acid soils !.versus the non-response in ...calcareous, alkaline soils may be [related to the root density effect iof compost at the different sites. iTrees in the very well drained /sand soak soil treated with .

CMSW were more densely ifoliated and showed little sign of i.water stress compared to the istressed, nontreated trees. CMSW iand CUPD have slow mineraliza- :tion rates, due to their moderate ito high carbon-to-nitrogen ratios i

(Eichelberger, 1994), so mulchesdid not increase nitrogen status ofthe tree (Widmer et al., 1997).

The mulches substantiallyimproved moisture-holdingcapacity of the soil, as demon-strated for compost applicationsto other Florida crops in similarsoils (Obreza and Reeder, 1994;Turner et al., 1994). Under morefavorable conditions for wateruptake, apparently fewer rootswere required to take up waterand water mobile nutrients (e.g.nitrogen and potassium), bringingabout a 30% decrease in rootdensity after compost applicationin well-drained sand soak soil.Hence, trees were able to producemore and larger fruit instead ofsupporting the high density ofroots required by a tree in the lowwater- and nutrient- holdingcapacity sand.

In finer textured, high pHcalcareous sand, where rootdensity was 25-35% of that in thesandy soil, compost apparentlyworsened the soil conditions(high calcium and somewhatalkaline pH) that normally limitperformance of certain rootstockslike Carrizo citrange (Castle et al.,1993). Although the mulch layerprovided a favorable site for rootgrowth in calcareous soil, yield oftrees was not increased even after3 years.

Thus, as for young trees, theprincipal effect of the compostwas improvement of soil water-holding capacity. This conditionenhanced pathogen reproductionin the mulches because P.nicotianae was favored by high soilmoisture (Duncan et al., 1993).However, compost appeared toincrease tolerance toPhytophthora root rot. Thebenefits of compost for increasingwater and nutrient availability insoils low in organic matterenhanced root health and uptakeefficiency, and thereby reducedthe impact of fibrous root disease



Observations of Cumposted MunicipalWastes on Florida Citrus

Sun-Ray and Southern farms are citrus grove operations of9,000 acres in Highlands County, Florida. During the past fiveyears, composted wastes have been applied to “sand soak"areas - sandy soils low in organic matter and pour exchangecapacity. The following are sume of the observations from theseapplications.

TimingThese materials are best applied during a period with

frequent rainfall. The summer period,, particularly the month ofAugust, is best. When cumpust is applied during a wet period, a”far better result is acquired,

ProdUcksWe have applied municipal wastes composted with biosolids,

urban plant debris campusted with biusulids, wuud mulchcomposted with biusulids, and various forms of compostedchicken manure. The campusted wood mulch with biosolidsproved to be the must consistent, and the tree response waslunger lasting. Chicken manure proved to be a good short termgreen-up to carry the trees through stress.

PlacementApplications in the tree row seem to give better response than

applications trunk to trunk across the bed, The tree rowapplication should be at a rate of at least twu tans per acre.

EconomicsA consistent cumpust product is required to enable an

efficient application. Suffieient benefit can be achieved if thecompost product can be applied under the tree fur less than $30per ton.

and probably other soil stressesas well.

Current Status ofResearch on Citrus

Some limitations in the use of compost have been encountered.Foremost is the availability of a .high quality source of compost inear the citrus industry that can ibe supplied with minimal delivery :cost. Most of the research has ibeen conducted with a co-composted municipal solid waste i

(approx. 90%) with waste waterresiduals (10%) from Sevierville,Tennessee, supplied byBedminster Bioconversion. Co-composted CMW has a favorablecarbon-to-nitrogen ratio (19: 1)and slow rate of N mineralization(Eichelberger 1994), so nitrogenleaching is not a concern.

The local CMSW (Reuter)tested in the early 1990s is nolonger available because the plantshut down. Evaluation of CUPDfrom another source has only

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recently been initiated. Agrower/cooperator conducted apreliminary trial with CUPD in1996 and reported that the mater-ial was very fibrous, containingpalm branch wastes and othercoarse woody residuals that madespreading difficult. The CUPDmaterial also may have been highin salts. Thus far, residual salts inthe Bedminster CMSW have notbeen a problem for citrus, due tothe very sandy soils that facilitaterapid leaching of salts and to thelong term nature of the responseon perennial citrus trees (at leastone year to detect growthresponses). The CUPD materialspread in 1997 did not share theproblems experienced with the1996 material, but this points outthe need for compost to be consis-tent in quality through time ifthey are to be used commercially.

Another major limitation toproceeding with further trials isthe availability of a commercialapplicator with the New Hollandor equivalent spreader in south-central Florida. Two cooperatorsrepresenting about 25,000 acres ofcommercial grove land are atpresent unable to use compostbecause they are unwilling topurchase a spreader, given thehigh capital cost (approximately$lO,OOO-14,000) and the uncertainavailability of high qualitycompost. Nevertheless, our resultshave stimulated their interest infurther trials of local compostsources, especially in sandy soilswith low organic matter.

Our current evaluation of thebenefits of compost used asmulches focuses on both youngand old groves in sand soak soils,where citrus trees have notresponded to extra water andnutrient inputs and, thus,probably are not manageablewithout soil amendments.Reduced rates of compostproduced by local municipalitiesin close proximity to the citrus



Figure 9-1. Composted municipal waste increased growth of young Orlando Tangelo treeson Cleopatra mandarin rootstock 17% (trees on right) compared to nontreated controls(trees on left) 2.75 years after application to a typical ridge soil (Candler fine sand) at theCitrus Research and Education Center, Lake Alfred.

Figure 9-2. Composted municipal waste (CMW) is applied to bearing citrus trees with aNew Holland 3000 side-discharge spreader as a 5-10cm thick mulch layer within therow to cover about 80% of the root system. The rate at this location ranges from150- I 70 metric tons per hectare of treated soil area.

i industry are now under evalua-i tion to further quantify the.! benefits and costs of compost.i applications. Although the: responses are positive, it isi unlikely that the horticultural.; benefits will offset the high cost.i of production and transport ofi compost. However, if landfilli space becomes a problem in the.i. future, the cost of production and.i transport of compost eventuallyi may be borne by the municipali-.i ties. For example, Los Angelesi County now pays citrus growers.i to accept urban plant debris fori use in their citrus groves (J. A.i Menge, University of California,.i Riverside, personali communication). 0..

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Growing Field Cropswith CompostThe use of urban plant debris compost can increase cropyield and decrease forage cost production.

I n Florida, tropical corn is .better adapted to local soils !than conventional corn .

varieties usually developed for the imidwest. Tropical corn acreage in :the southern United States .

increased from about 1,500 acres iin 1985 to approximately 45,000 :.acres in 1991. Recent estimates :indicate a potential of 150,000 to !200,000 acres of tropical corn ;with the primary use as a late !.season planted silage crop.

....Sorghum [Sorghum bicolor L. i(Moench)] is another valuable isilage crop that is adapted to late isowing conditions. In Florida, :about 18% of the 142,000 acres of /full-season corn and 5% of the42,000 acres of double-crop cornis grown with conservation tillage

....

management. A significantacreage of soybean (Glycine maxL. Merr.), cotton (Gossypiumhirsutum L.), small grains, foragesand other crops, such asvegetables, peanut (Arachishypogaea L.), tobacco (Nicotiana ...tabacum L.) , etc., are also grown ion Florida’s infertile and highly !leachable sandy soils.

...Land on which these crops :

are grown offers an opportunity ito recycle urban plant debris :(UPD, also known as yard waste) i.in a safe and effective manner, iwhile at the same time increasing /crop yield and decreasing cost of i

production. Mulching and addi- i.tion of organic material also may :increase the tolerance of plants to /nematode damage.

.

...Impact of UPD Compost on i..Soil Properties

.....Large applications of UPD ;..

can have a major impact on ....improvement in soil quality, often iassociated with a positive crop iresponse.

Soil nutrients. The UPDused in one study had a carbon- :to-nitrogen ratio of approximately i35: 1 (Gallaher and McSorley, i1995a). In order to alleviate nitro- igen-rob (N-rob) of crops, the icompost needs to be incorporated ;into the soil a minimum of 3.5 to :4 months before planting to allow !equilibration to occur (D.A. :Graetz, Soil and Water Science :Department, University of iFlorida, personal communica-tion). Nitrogen-rob does notappear to be a major problemwhen the UPD is used as a mulchand the required addition ofnitrogen fertilizer is placed belowthe mulch (Gallaher and

.......McSorley, 1995a). ....

The cumulative applications iof UPD totaled 360, 300, and 240 itons/acre for some treatmentsdepending on the experiment iduring a 3-year period. Soil :organic matter more than doubled i

R.N. GALLAHERDEPARTMENT OFAGRONOMY

thIVERSITYOF~ORIDA

GAINESVILLE, FLORIDA

in some treatments over a 3-yearperiod. Significant increases werealso measured in soil pH,extractable plant nutrients, cation-exchange capacity and water-holding capacity. Tests are nowunderway to determine if areduction in the costly input offertilizers and lime may be offsetby the addition of compost.

Soil water storage. UPDcompost applied as a mulchresulted in the greatest amount ofsoil water storage in the top 2 feetof soil in three Florida UPD-treated corn experiments. In oneexperiment, the UPD mulch treat-ment had 2.3 1 acre-inches morewater stored in the top 2 feet thanthe control. The estimated valueof this soil water storage over thecontrol ranged from $23.92/acreto $41.46/acre, depending on thetype of irrigation that would berequired to apply the sameamount of water. Use of UPD asa mulch conserved 6 to 10% moresoil water than the same amountof UPD incorporated, and 40% to75% more stored soil watercompared to no UPD (Gallaherand McSorley, 1994).

Long-term effects. All of thesoil properties, including organicmatter, nitrogen, and cation-exchange capacity, were dramati-cally increased from applicationof UPD, the magnitude of which


CHAPTER 10: GROWING FIELD CROPS WITH COMPOST

was highly correlated with theamount of UPD applied. Organicmatter reached a peak in the thirdyear after UPD application andseemed to be maintained for thenext two years at the highestUPD rates. Soil nitrogenappeared to peak one year afterthe last application of largeamounts of UPD. Extractablenutrients were also increased byapplication of UPD (data notshown). Data seemed to fluctuatesomewhat for phosphorus,perhaps as a result of more thanone mechanism, such as farmerfertilization, soil fixation versusextractable, and crop uptake. It isclear that large quantities ofphosphorus was applied in UPD.

Extractable potassium peakedthe year of the last application ofUPD then declined. This may beconsistent with what would beexpected, since large quantities ofpotassium are taken up by a corncrop, potassium is highly leach-able in a sandy soil, and it issomewhat replaceable onexchange sites even though, inthis case, the cation-exchangecapacity had increased.

Extractable calcium andmagnesium appeared to peak andbe maintained, or in the case ofcalcium, may have even increasedafter the last year of UPDapplications.

The cation-exchange capacityseemed to peak one year after thelast application of large amountsof UPD. Continued soil analysesof these plots in future yearswould be useful in determiningthe duration of the impact thatUPD has on continuing changesin soil variables.

Compost Effects onNematodes

The increased nutrient levelsand water-holding capacity ofsoils amended with compost mayincrease plant tolerance to nema-tode damage (Watson, 1945).

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There is evidence that the addi-tion of certain organic com-pounds may stimulate fungal par-asites of nematodes (Rodriguez-Kabana, 1991). However, themost important effect of organicamendments on plant-parasiticnematodes may be the reductionof populations from toxic byprod-ucts of decomposition. Ammoniaand urea were shown to suppressseveral nematode species in tests,and the decomposition of someforms of organic nitrogen canrelease byproducts which aretoxic to nematodes (Rodriguez-Kabana, 1986). The most effectiveof these amendments are thosewith low carbon-to-nitrogen ratiosthat can release ammonia into thesoil (Rodriguez-Kabana, 1986).

Regardless of the mechanisminvolved, the addition of organicamendments may serve to allevi-ate some of the adverse effects oncrop growth caused by plant-parasitic nematodes. Of theplant-parasitic nematodes foundat some UPD Florida field cornresearch sites, Paratrichodorusminor was significantly decreasedfrom application of UPD(McSorley and Gallaher, 1996).Other nematodes, such asMeloidogyne incognita, were notconsistently affected by compostapplications. Effects of the highcarbon-to-nitrogen-ratio composton these agricultural sites mayprovide beneficial effects onlyafter several years of UPDapplication.

In another study, transplantedseedlings of squash (Cucurbitapepo) and okra (Hibiscus esculentus)and the use of conventionaltillage incorporated UPDappeared to result in best yields(Gallaher and McSorley, 1995b).These results were based on limit-ed data and a limited time for soilproperties to be impacted bycompost and to translate intocrop response. Totally differentresults may be found between

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conventional tillage versus no-tillage after soil properties havebeen enhanced from use of UPD.

From this same study, it wasconcluded that the main benefitof UPD against nematodes didnot appear to be reduction ofnematode populations, butimproved growth and tolerance ofhost plants in nematode-infestedsites. Sweet corn yields wereequal for UPD treatments bothconventional tillage-incorporateand no-tillage-mulch, and bothgave yields superior to the con-ventional tillage control withoutUPD (Gallaher and McSorley,1995b).

Response of Corn toUPD Compost

There was a consistent trendfor corn forage yields to increaseas the cumulative total UPDapplication rate increased. A highcorrelation was found betweencorn forage yield (Table 10-l) andall of the soil property variablespresented. These data also showthat the effects of UPD applica-tion, at the high rates used inthese studies, had a long-termbenefit on soil quality and cropyield, extending well beyond thelast year of UPD application(1994). It has not yet been deter-mined how long these benefitswill persist.

Increased corn forage yieldsfrom use of UPD ranged from 2.5ton/acre to 6 ton/acre, valued at34 / ton (based on 30% drymatter), depending upon theexperiment. Increased yield waspositively correlated with theincreased soil organic matter,improved soil fertility conditions,and greatly increased soil waterstorage capacity. Mulchedno-tillage UPD treatmentsconsistently had greater amountsof stored soil water compared tothe conventional tillage-incorporated UPD treatments(Gallaher and McSorley, 1994).


CHAPTER 10: GROWING FIELD CROPS WITH COMPOST

0

0 t o n YWC/a

120 ton YWC/a

1993 1994 1995 1996 1997Y E A R

Table 10-l: Compost Use and Corn Silage Yield. Corn silage yield from use of yard wastecompost (YWC) on Haufler Farm, Gainesville, Florida (values of YWC are in ton /acrecumulative from applications in 1992, I993 and 1994.

In California, test blocks showedthat when the organic matter levelis raised through large scaleaddition of organic amendments,impressive changes take place(Woolley, 1995). When theorganic matter is doubled to 4%, ithere is a four- to five-fold .

increase in water retention, .resulting in a 10% to 25% .reduction in irrigation required i.in a normal rain year. Further iresearch is required to determine :what periodic level of re-treat- iment with compost will sustain :these benefits. .

Economics of Cornposting iIn 1989, Florida produced an i

average of 16 tons per acre corn isilage on nearly 20,000 acres of icorn silage harvested. Economic ibenefits from reduction of ifertilizer inputs and increased iwater conservation to corn silage !alone could amount to $200 peracre. For example, depending on :the nutrient concentrations and :ratios in composted waste

....materials, a typical net return of i.

$322 per acre (30 tons silage peryear) from double-cropped cornfor silage was reported byGallaher et al. (1991).

If nutrients from biodegrad-able solid waste were used insteadof fertilizer to replenish soilnutrients removed by the cornsilage crops, the net return wouldincrease to $536 per acre, a net$2 14 per acre increase. If UPDprovided these nutrients on 5,000acres of double-cropped cornsilage, a fertilizer savings of over$1 ,000 ,000 would be realized thefirst year alone.

These savings were calculatedbased on the assumption that,because of societal benefits,municipalities wish to recyclebiodegradable solid waste onfarmland and, therefore, therewould be no cost to the farmer formaterials, hauling and spreading.Purchase and transportation costsmight result in no financialadvantage to the farmer fordisposal of or use of UPD onsandy soil farmland, even thoughsoil properties and corn forage

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yields increased. If the cost ofUPD and its transport to the fieldwere to be as much as $2/ton,then the advantages of the UPDessentially disappear, and costwould exceed the price of silageat the farmers storage pit(Hildebrand et al., 1997). Thechallenge for future researchersand policy-makers is to balancesocietal and economic benefits. 0



Use of CompostsVegetable CropsWhen used withcrops a boost.

on Florida’s

care, compost can give Florida’s vegetable

F lorida is a major vegetable- :producing state, with 418,000 :acres under cultivation each i

year (Florida Agricultural..

Statistics Services, 1997). Sandy !soils used to grow Florida

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vegetables have low nativefertility, so they require relatively ihigh fertilizer inputs. However, i.minimizing fertilizer leaching orrunoff has become important as aresult of potential negativeenvironmental impacts. If waterand fertilizer conservation couldbe increased, grower input costsand negative environmental ..effects could potentially decrease. :

In recent years, composts iproduced from a wide range of i.waste materials have become !available in Florida on a large iscale (Smith, 1995). While

...

environmental regulators are :.mainly concerned about trace :metal concentrations in compost, :growers have different interests /once compost has passed .regulatory health and safety istandards (Ozores-Hampton et :al., 1998a). From a commercial [vegetable grower’s point of view, :compost quality is judged by its /moisture and nutrientconcentration, pH, soluble salts, :organic matter concentration, ;carbon-to-nitrogen (C:N) ratio, iwater-holding capacity, bulk :density, cation-exchange capacity, !

MONICAROZORES-HAMPTONANDTHOMASA.OBREZA

UNIVERSITY OFFLORIDA/INSTITIJTEOFFOODANDAGRICULTWULSCIENCES

SOUTHWEST FLORIDARESEARCHANDEDUCATIONCENTER

IMM~KALEEJL~RIDA

particle size, presence of weedseeds, and odor (Ozores-Hampton, et al. 1998a).

Pros and Cons of ApplyingCompost to VegetableCrops

When compost is incor-porated into soil, observedbenefits to crop production havebeen attributed to improved soilphysical properties. Compostusually contains large quantitiesof plant-available micronutrients(Ozores-Hampton et al., 1998a).However, soil improvements aremainly attributed to increasedorganic matter concentrationrather than increased nutrientavailability. (Gallardo-Lara andNogales, 1987). Significantquantities of nutrients(particularly nitrogen, phos-phorus, and micronutrients)become bioavailable with time ascompost decomposes in the soil.Amending soil with compostprovides a slow-release source ofnutrients, as opposed to mineralfertilizer, which is usually water-soluble and is immediatelyavailable to plants.

Crop injury has been linkedto use of poor-quality compost,such as that from early stages ofthe cornposting process (Zucconiet al., 1998a). The type and

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degree of plant injury is directlyrelated to compost maturity andsoluble salt content. Optimumchemical and physical parametersfor composts that might be usedin vegetable crop production arelisted in Table 1 l-l.

In Florida, soil application ofimmature compost consistentlyresulted in “N-immobilization,”where available forms ofinorganic N were converted tounavailable organic N followedby growth inhibition of vegetablecrops such as beans, corn,peppers, tomatoes, and squash(Kostewicz, 1993; Gallaher andMcSorley, 1994; Bryan et al.,1995). When immature compostis applied and a crop is plantedimmediately, growth inhibitionand stunting may be visible for 40to 60 days. When using compostwith C:N ratios higher than 25 or30, N fertilizer should be applied,or planting delayed for 6 to 10weeks to allow the compost tostabilize in the soil (Obreza andReeder, 1994).

Research on vegetablecompost utilization in Floridahas established several potentialapplications: soil amendments,soil-borne disease suppression,biological weed control,alternative to polyethylene mulch,and as a transplant media.


CHAPTER 11: USE OF COMPOSTS ON FLORIDA’S VEGETABLE CROPS

TABLE 11-lPhysical properties of compost used in vegetable production*.

Passes 1 inch screen

Uncomposted materials disseminate weeds

Z FDACS, 1995.YG.I = (% seed germination x root length growth in % of control)/ 100.

Compost as a SoilAmendment .

Amending Florida soils with icomposted materials such as ibiosolids, MSW, and urban plant :debris (UPD) has been reported i

’to increase crop yields of bean,black-eyed pea, okra, tomato,squash, eggplant and bean, water-melon and tomato, corn, and bellpepper (Bryan and Lance, 1991;Ozores-Hampton and Bryan1993a, 1993b; Ozores-Hamptonet al., 1994b; Obreza and Reeder,1994; Gallaher and McSorley,1994). In calcareous soil,application rates of biosolids

.

compost as low as 3 to 6tons/acre resulted in crop yieldincreases for tomatoes, squash,and beans (Bryan and Lance,199 1; Ozores-Hampton et al.,1994b). In sandy and calcareoussoil, MSW compost applicationrates of 40 tons/acre resulted incrop yield increases for bean(Obreza and Reeder, 1994).(Figure 1 1- 1) Contradictory cropresponse results were found whena compost with low nutrientcontent was compared to atraditional fertilizer program.However, combining suchcompost and inorganic fertilizerhas generally been more effectivein producing a positive plant

..

response than separate applica-tion of either material alone.

One concern of usingbiosolids or MSW-basedcomposts is the possible presenceof unwanted elements in thecompost and their uptake bycrops. Compost that does notmeet EPA 503 standards formetals concentration in biosolidscannot be marketed and is thusunavailable to be applied toagricultural land. Research inFlorida on tomatoes and squashgrown on calcareous soil wherebiosolids, MSW, and co-composted biosolids-MS W thatmet the 503 standards wereapplied showed no trace metalaccumulation in the edible plantparts (Ozores-Hampton et al.,1994b and 1997).

If all of Florida’s organicfraction of solid waste wasconverted to compost, it couldeasily be assimilated by theFlorida vegetable industry. If only20 tons/acre of compost (freshweight) were applied to each ofthe 418,000 acres of vegetablesannually grown in Florida, 8.4million tons of compost could berecycled each year (Smith, 1994).The actual rate and frequency ofcompost use should be deter-

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mined by compost properties such i

as nutrient concentration or Nmineralization rate, and soilphysical and chemical properties.

Soil-borne DiseaseSuppression

The colonization of compostby beneficial microorganismsduring the latter stages ofcornposting appears to beresponsible for inducing diseasesuppression. Compost does notkill the pathogens that causedisease as fungicides do. Instead,compost controls the pathogensby keeping the beneficial micro-organisms active and growing.Therefore, pathogenic agentseither will not germinate or willremain inactive (Ozores-Hamptonet al., 1994a).

In Florida, few experimentsin vegetable crop productionunder field conditions haveinvestigated the use of compostin controlling soil-bornepathogens. Municipal solid waste(MSW) was incorporated intocalcareous soil in Dade County at36 and 72 tons/acre andcompared to an untreated control(Ozores-Hampton, et al., 1994a).A two-crop rotation of bushbeans and southern peas wereseeded. Bean emergence and yieldwere improved by 25% in the

40COMPOST USE IN FLORIDA


Figure 11-1: M S W compost application rates of 40 tons/acre (top) as compared with the no compost application (bottom) onwatermelon. Comvost-treated plots yielded 22.35 tons/acre compared with 16.15 tons/acre in control plots with no compost.

.

Hampton et al., 1998b). Weed and the presence of phytotoxicseed germination inhibition by i compounds (fatty acids) in theburial under mulch is due to the i immature compost (Ozores-

compost treatment compared to ithe untreated control. Ashy stem i.blight of bean caused byMacrophomima phasolina was :severe in areas with no compost iapplication, but was almostcompletely eliminated where :MSW compost had been applied i(Figure 1 l-2). MSW compost ireduced the damage by

...Rhizoctonia root rot in southern ipea considerably compared with ithe untreated control. In the areas /with no compost application, !severe infections caused plant istunting and premature death, iwith significant yield reduction. i

Biological Weed Control :Weed growth suppression is i

an important attribute of surface- iapplied mulch. An organic mulch !suppresses weeds by its physical ipresence as a surface cover, or by ithe action of phytotoxic corn- :pounds contained in it (Ozores- i.

lack of growth-promoting factors isuch as light, temperature, or :moisture. Chemical effects of ;phytotoxic compounds (volatile ifatty acids and/or ammonia) in icompost can decrease weed seed :germination. In Florida, a water iextract of 3-week-old UPD and ;immature MSW compost

...decreased germination of several iperennial and annual weeds in ipetri dishes (Shiralipour et al., i1991). Under field conditions, iapplication of immature 4-week- [old MSW compost at 3 inches (45 iton/acre) or greater thickness :.completely inhibited weedgermination and growth for 240 idays after treatment in vegetable icrop row middles. Inhibition of :germination or subsequent weed !growth may be attributed to both ;the physical effect of the mulch i

Figure 11-2: MS W compostapplication rates of 72 tons/acre(front) nearly eliminated ashy stemblight, compared with the no compostapplication (back) on bush beans.



Checklist for Compost :

Utilization on Vegetable Crops1. Use of immature compost can c a u s e detrimental effects on plantgrowth. H&h C:N ratio compost can result in N-immobilization if it isbelow 25:1 to 30:1. We recommend assaying compost for the presence ofphytotoxic compounds using a cress seed germination test. In this test, acompost sample is saturated with water, and the extract is squeezed fromthe sample. A portion of the extract is used to moisten filter paper i n apetri dish, on which mess see& are placed and allowed to stand fur 24hours. The germination index (GI) is measured as GI = [(% cress seedgermination x root length in % of the control)100] . If GI is less than60, allow about 90 days between the time of compost application andplanting of the crop, o r apply nitrogen fertilizer. For example, if cressgermination and root length on compost was 40% and 1 inch, and thecontrol 80% and 2 inches, respectively, therefore we obtained a 50% cressseed germination and 50 % root length as % of the control Thus, theGI = 25, indicating immature compost. An alternative measure is t ocontinue composting the material to maturity before it is applied.

2. Most vegetable crops are sensitive to high soluble salts, especiallywhen they are direct-seeded. We recommend measuring the soluble saltsconcentration of a saturation extract. If the electrical conductivity (EC)is below 6.0 dS/m, no salt toxicity should o c c u r . If the EC is above 6.0dS/m, the amended soil should be leached by rain or irrigation withwater before planting seeds (only a few crops can tolerate this salt level).

3. Lack of equipment to spread cumpust in vegetable fields is a concern.We encourage cumpust facilities to play an active role in developingspreading equipment.

Source: Ozores-Hampton et al., 1998a.

Hampton et al., 1998a). Similarweed reduction was obtained with imature MSW compost (100 itons/acre) in row middles of bell :pepper compared with an .untreated control, but herbicide :provided improved weed control :over mature compost (Roe et al., i1993b).

Alternative to Polyethylene iMulch

Polyethylene mulch regulates :soil temperature and moisture, !reduces weed seed germination :and leaching of inorganicfertilizer, and is a barrier for soil jfumigants. Removal and disposal iof polyethylene mulch has been a :

major production cost to Florida :growers. Therefore, utilization of icomposted waste materials in :combination with living mulches iin a bell pepper productionsystem was investigated (Roe et ial., 1992, and 1993a). Traditional !raised beds were covered with :polyethylene mulch, MSW, wood i.chips, or biosolids-UPD co- .compost (100 tons/acre), and bed :.sides were either planted with a iSt. Augustine grass living mulch /or not planted. Bell pepper yields :were higher on compost mulch iplots than on unmulched plots but ilower than on polyethylene- :mulched beds.

Compost as a TransplantMedium

The vegetable transplantindustry relies on peat moss as amajor ingredient in soilless media(Vavrina and Summerhill, 1992).Peat is an expensive, non-renewable resource. In Florida,alternative soilless media has beeninvestigated to grow tomato,cucumber, bell pepper, and citrusseedlings (Vavrina, 1994; Roe andKostewicz, 1992); Stoffela et al.,1996). Seed emergence andseedling growth was similar totraditional peat:vermiculite mediawhen peat was partially replacedwith compost. Negative growtheffects were reported when themedium was 100% compost,especially when immature,unstable compost was used or thecompost did not have adequatefiber content to assure a desirablebulk density. 0



Compost Uses for thelandscape and NurseryIndustriesHigh quality compost frequently compares favorably withpeat as a growing medium for Florida's nursery andlandscape plants.

GEORGE E. FITZPATRICK AND

DENNISB. MCCONNELL

ENVIRONMENTAL HORTICULTURE DEPARTMENT

thIVERSITY OF FLORIDAGAINESVILLE, FLORIDA

0 f all the different agricul- ;tural uses for compost iproducts, use as a growing :

medium component in orna- !mental crop production frequently ireceives high priority because of ithe relatively high value of

..nursery and greenhouse crops and !the continual cultural requirement ifor organic matter for rooting isubstrates (Slivka et al., 1992; iTyler, 1993; Tyler, 1996). Every /time a container plant is sold, the irooting substrate is sold with it, i.necessitating the need for new ipotting mixtures to start new crop !production cycles. ...

The attractiveness of ....ornamental crops as outlets for icompost product marketing does i.not come without cost, however. iSince the plant’s root system is in idirect and continual contact with ithe compost product, any con- icerns regarding compost quality i.are most acute with container icrops. Plant producers must keep iin mind that the way compost [products should be used is not i.necessarily the same way that nat- iural humus products, such as ipeat, are used. ...

Using Compost for iOrnamental Crop ...Production

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Compost materials have been ;.used successfully to grow a wide i

spectrum of nursery crops, from iflowering annuals (Wootton et al., i1982) to container-grown tropical itrees (Fitzpatrick, 1985). In a idemonstration project conducted !in 1979-1980 at a commercial inursery in southern Florida, anumber of container-grownornamental species grew tomarketable size significantly fasterthan plants grown in a growingmedium composed of 6 peat: 4sawdust: 1 sand, by volume(Fitzpatrick, 198 1). One of thespecies tested, dwarf oleanderNerium oleander, grown in IO-inch idiameter containers for 5 months, !averaged approximately 1.25 :times larger when grown in the /compost mixture as compared to ithe control (Figure 12-1).

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Moreover, compost products have ibeen successfully used in field i.nurseries as soil amendments to :increase productivity in varioustree species (Gouin, 1977 -Gouin and Walker, 1977).

Numerous other researchstudies and reviews have beenpublished on how compostproducts can be used to improve iproduction of nursery crops. iSanderson (1979) reviewed a large inumber of published studies and i.reported significant increases in iproductivity across a wide variety !of nursery crops. More recently, /Shiralipour et al. (1992a) ..

reviewed published studies oncompost use in a wide variety ofcrops, including nursery crops,and reported significant increasesin crop productivity.

Unlike other applications ofcompost in agriculture, the stand-alone container medium categoryrequires the highest quality ofcompost. One example of theinfluence of compost quality oncompost performance as acomponent in a horticulturalgrowing medium is the level oftotal salts in the substrate. Thelevel of soluble salts in compostsmade from sludges stabilized withferric chloride and lime may beconsiderably higher than incompost made from sludge thathas been stabilized using a wet-airoxidation process. One studycompared the use of these twotypes of sludges for growing thenon-salt tolerant container cropsSpathiphyllum Mauna Loa andSchefflera arboricola. The plantsgrown in the compost with highersoluble salt levels were signifi-cantly smaller than plants grownin composts with lower solublesalts. However, both compostproducts resulted in plants thatwere significantly larger thanplants grown in a control mediumconsisting of 40% peat, 50% pinebark and 10% sand (Fitzpatrick,1986).


CHAPTER 12: COMPOST USES FOR THE LANDSCAPE AND NURSERY INDUSTRIES

Figure 12-1. Dwarf oleanders (Nerium oleander) grown in I O-inch diameter containersfor 5 months in a trial conducted at a commercial nursery averaged I.25 times largerthan plants grown in a control growing medium comprised of the nursery’s standardmix of 6 peat:4 sawdust:1 sand, by volume (Fitzpatrick, 1981).

Figure 12-2. West Indian mahogany Swietenia mahagoni grown in compost alone withno fertilization and irrigated with well water (second from right) did not achieve growthcomparable to trees grown in a peat, pine bark and sand medium fertilized at normalnursery crop rates (control [right]). Trees grown in compost medium with no fertilization andirrigated with sewage effluent (secondfiom left) grew larger than trees grown in peat, pinebark and sand medium, with no fertilization and irrigated with secondary effluent. Compostmedium did not supply sufficient nutrients in fast growing tress such as mahogany and schef-flera. In slower growing trees, the compost and effluent supported growth rates comparable tothe rates observed in the control (Fitzpatrick, 1985).

Growers also should be aware i provide all of an ornamental.that while many compost i crop’s requirement. For example,products contain significant levels i in one study in which tropicalof certain plant nutrients, they i trees were grown in containers,rarely contain these nutrients in i the compost products did notsufficient concentrations to i provide sufficient nutrients when

; used without fertilization,.i especially in fast growing trees.i such as schefflera (Brassaia: actinophylla) and West Indian.i mahogany (Swietienia mahagoni)i (Figure 12-2) (Fitzpatrick, 1985).i In this same study, sloweri growing trees, such as pinki tabebuia (Tabebuia pallida) andi pigeon-plum (Coccoloba.i diversifolia), grown in biosolids.i compost and irrigated withi secondary treated sewage effluent,i grew at rates that were noti significantly different from ratesi observed in trees grown in a peat,i pine bark and sand mediumi fertilized at normal nursery crop.i levels. Apparently, the levels of.i nitrogen (N) in the effluent.i (average 6.8 mg/L, SD=5.8) werei sufficient to augment nutrients.i provided by the compost medium.i in the slower growing trees, buti not in the faster growing species.....[ Expanding Horizons

Careful attention to growingi medium characteristics can allow.i faster and more economicali production of ornamental crops.i Since nursery crops have a.i recurring need for a growing.i medium as each growing cycle is.i completed, compost marketers.i have the opportunity to develop.i products that can be very.; attractive to ornamental planti growers. Provided the composti products are made with emphasis.i on quality, it is likely that use ofi compost materials will continuei to expand in nursery crop.i production. 0....

4 4 C O M P O S T U S E I N F L O R I D A


Use of Compost onTurfgrasses

JOHN L. CISAR

Compost may help build better turfgrasses on some UNIVERSITY OF FLORIDA

148,000 acres of golf courses in Florida. FORT LAUDERDALE RESEARCH AND EDUCATION CENTER

FORT LAUDERDALE, FLORIDA

‘here are more than 5 millionhomes with turfgrass lawnsin Florida, and more than

1,300 golf courses, an increase ofmore than 15 percent since 1994,The average Florida golf course is114 acres in size. Thus, more than148,000 acres in Florida are dedi-cated to golf courses. Golf coursemaintenance expenditures average$3,585 per acre annually. Moneygenerally is available and will bespent by golf courses for mainte-nance practices that are proven tobe beneficial.

Beneficial Effects ofComposts on Turfgrassesin Florida

Numerous articles recentlyhave discussed the potential useof compost on golf courses. Mostof these focus on using compostfor topdressing, and some discussthe use of golf course-generatedorganic waste as compost feed-stock. However, there is little doc-umentation of actual compost useon golf courses, other than asmulch around ornamental plant-ings. The use of compost as a soilamendment during golf courseconstruction is rarely discussed.

Because of a lack of scientificstudies aimed specifically at utiliz-ing compost in golf courses inFlorida, discussions on the subjectwill be based upon inferences

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GEORGE H. SNYDER

UNIVERSITY OF FLORIDA

EVERGLADES RESEARCH AND EDUCATION CENTER

BELLE GLADE, FLORIDA

from uses of composts in otherturfgrass situations and fromother regions. Detailed, specific,proven recommendations forcompost use on golf courses inFlorida cannot be given at thistime.

Of the research that has beenconducted on golf courses inFlorida, most has related to usingcompost as a soil amendment toimprove the native sand soilswhich generally are droughty,infertile, and have little capacityto retain nutrients and other agro-chemicals. We have consistentlydemonstrated that overall turf-grass quality, in terms of visualappearance and vegetative density,is improved by the incorporationof composts in the root zone atrates up to approximately 30% byvolume (Cisar and Snyder, 1995;Snyder and Cisar, 1996). In thesestudies, various municipal com-posts were spread over the soilsurface at a depth of approxi-mately two inches and incorporat-ed by rototilling to a depth ofapproximately six inches.

Particularly in the monthsshortly following compost appli-cation, drought resistance hasbeen observed (Cisar and Snyder,1995). The time following a rain-fall or irrigation event until turf-grass wilting was observed to beincreased in those plots that

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received the compost incorpora-tion. In greenhouse studies,leaching of several organophos-phate insecticides was reduced bycompost addition, and theaddition of compost did notincrease leaching of nitrate orphosphorus (Cisar and Snyder,1995).

Compost clearly providesmuch needed plant nutrients forturfgrass growth, which isreflected as increased uptake ofnutrients by turfgrass grown incompost-amended soils (Table 13-1). In one compost source studythat is still underway, the positiveturfgrass growth and visual turf-grass quality effect of compostincorporation has been observablefor more than 2.5 years.

We believe the major nutri-tional benefit of the compost isdue to the quantity of nitrogen itcontains, which is slowly releasedto the turfgrass over time. In thisregard, some sources of compostcontain more nitrogen thanothers. Those that are amendedwith biosolids have analyzedhigher in nitrogen than compostsmade exclusively from urbanplant debris, and turfgrass growthhas been greater in soils amendedwith such materials (Snyder andCisar, 1996). The compostscontain other nutrients as well,but some fertilizer may be needed


CHAPTER 13: USE OF COMPOST ON TURFGRASSES

TABLE 13-1Effects of Compost on Nutrients in Turfgrass

20/5/93

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l **, *, and ns represent P<0.01, 0.05, and P>0. 10, respectively.

T A B L E 1 3 - 2Relationship Between TurfgrassTopdressing Rates and Depth.

Application Applicationrate depth

1.0 I 0.32

to provide a balance of nutrientswith respect to the nitrogencontent of the compost. In thisregard, potassium may berelatively low in some composts.

Potential Uses of CompostAmendments in Golf Turf

A number of articles haveappeared in golf course trademagazines in recent years encour-aging the use of compost on golfcourses. However, in most cases,little information is presented thatspecifically describes the use ofcompost. For example, Wilkinson(1994) listed many benefits of

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using compost on golf courses,but provided few examples of itsuse or specifics about usingcompost on various portions ofthe course. Thus it appears thatthe task still remains to combineexisting data on the benefits ofcompost to turfgrass with a ......consideration of the various ..

possible uses on a golf course in iorder to suggest methods and ;markets for compost uses on golf :courses.

Golf courses can be compart- imentalized into four main sectors: /greens, tees, fairways, and roughs. !On an area basis, fairways and :roughs account for more than 90 i..percent of the golf course.

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Although greens and teesconstitute only a small portion of ithe entire area, they receive a vast :majority of the overall mainte- :nance dollars and effort expended i.on the course.

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Greens Construction iModern greens generally are i

constructed according to rigid ispecifications delineated by the :

United States Golf Association(USGA). The specifications allowfor inclusion of organic matter inthe form of sphagnum peat, butthe use of other materials is notrecommended. It may be possibleto substitute compost for sphag-num peat, but any such mixtureshould be analyzed in the labora-tory before use to confirm adher-ence to USGA-specifications forthe root zone mix. For this rea-son, no blanket recommendationcan be made for the use of com-post in greens construction.

TopdressingRoutine soil application on

the surface of greens (topdressing)to control thatch and increasesurface smoothness and ball rollon mature and new golf coursegreens is an essential golf coursecultural management operation.Topdressing adds a thin layer ofsoil, usually no more than 1/8-inch depth at the surface of theturf, after which it is incorporatedby mechanical and physicalaction with brushes or mats. Atthis rate, approximately 0.4 cubicyards of topdressing per 1000 ft2of surface area are required(Table 13-2). Frequency and ratesof topdressing are based ontargeted use. In Florida, top-dressing is applied to bermuda-grass as often as bi-weekly. Lightrates of topdressing are preferredfor quality greens (Beard, 1982).Topdressing rates range from 0.05yards per thousand square feet forwell-performing greens withminimal thatch to 0.4 cubic yardsper thousand square feet forbermudagrass greens with athatch problem (Beard, 1982).Greens in Florida generallycomprise 6 to 8 thousand squarefeet each.

Topdressing materials shouldclosely match the texture of theexisting soil medium if soil rootzone modification is not the goal.Soil layering should be avoided as


CHAPTER 13: USE OF COMPOST ON TURFGRASSES

this reduces water and air move- ;ment through the profile. Thus, :topdressing may not consist ipurely of compost. Instead, itopdressing materials generally iconsist of sand- and soil-sized :particles, in addition to organic i.materials (Beard, 1982).

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Furthermore, organic matter i.addition to topdressing is an area iof controversy. Some experts irecommend pure sand for top- idressing of greens, as sufficient iorganic matter is found in thatch i(McCarty and Elliott, 1994). On ithe other hand, Adams and Gibbs i(1994) recommend topdressing iapplications with a low amount of ’organic matter to dilute the resid-ual organic matter and to avoidthe increased surface hardnessfrom pure sand applications.

Regardless of the philosophyon the benefits of includingorganic matter in topdressing,many golf course superintendentsroutinely apply topdressings thathave organic matter mixed in asan additive to improve nutrientand water retention. A number oforganic materials have been usedin soil mixtures, with peats beingthe most popular. Composted leafblade materials generated by thecourse also have been used.Following current managementpractices, more compost would beutilized in topdressing for greensthan for any other portion ofcourse, because topdressing is notroutinely used on the remainderof the course. Greens are mowedvery closely, so compost used intopdressing must be very fine, andnot contain fragments of metal,glass, and plastic.

TeesTees probably could be

constructed with 10% by volumecompost, or perhaps somewhatmore, and there would be anagronomic benefit for the grass.Initial “grow-in” likely would befaster, less fertilizer would be

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required for maintenance, andirrigation might be reducedsomewhat.

FairwaysFairways constitute the bulk

of the golf course acreage.Compost probably could be usedbeneficially in fairways duringconstruction, with incorporationin the surface soil at rates of 10 to20% by volume, and up to 30% inwell drained areas. Bunkers andfairway mounds often aredroughty and difficult to manage,and compost use in bunker andmound construction might beespecially valuable. Utilization ofcompost in fairway constructioncould aid in “grow-in” and main-tenance, reducing the requiredamount of fertilizer and possiblywater for at least several years.

RoughsRoughs are second in area

only to fairways. Compostincorporation into areas devotedto roughs could be especiallyuseful, since fertilization andirrigation probably could bereduced. In all but poorly drainedareas, compost incorporation atrates up to 30% by volume shouldbe permissible.

The Role of Compost inDisease Management onGolf Courses

Intensively managed golfgreens are particularly exposed tostresses caused by plant diseases.In recent years, alternativemethods of disease control,including the use of composts andbiological control agents, havebeen suggested (Nelson, 1992).The mechanism of control isthought to be through suppressionof disease by either a direct effectof microorganisms in the composton the pathogen or from morefavorable soil conditions whichencourage soil microfloradiversity, leading to suppression.

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Cornposting Golf CourseWastes

Using golf course leaf bladeclippings and other plant-derivedmaterials as an organic amend-ment to topdressing has been an“in-house” practice of somesuperintendents for a number ofyears. However, there has been lit-tle scientific study to base recom-mendations for using suchmaterials. Potential problemsarising with incorporating organicmatter from such sources includeintroduction of pathogens, weeds,nutrient-rob from poorlycomposted materials, sourceinconsistency, and play interrup-tion from poorly sized organicmaterials. Golf courses may alsobe limited by low storage capacityand availability of compostedtopdressing and labor support toadequately prepare the top-dressing materials. Companiesthat could conduct the compostoperation at the golf course, andvendors who could supplycomposted topdressings, asneeded, could fill this marketplaceniche (Ostmeyer, 1993).

For golf courses that wantto do on-site preparation ofcomposted topdressings, fewguidelines exist. The dry soiltopdressing mix should be sievedto remove large objects and mayrequire fumigation to kill offpathogens, weed seeds, andundesirable vegetative propagules(Beard, 1982). The organic matterfraction portion should be sizedto avoid segregation afterapplication to the turf surface.According to Beard (1982), thefinal preparatory step for thetopdressing mix should becomposted for a period of up toeight to ten months to regeneratesoil flora and fauna. Compostedtopdressing should be stored in awell-ventilated shed and besufficiently dry at the time ofapplication (Beard, 1982). 0



Compost Use on Forest landsUsing compost on Florida’s forest lands may be an acceptablemeans of recycling organic residuals.

H. RIEKERKDEPARTMENT OF FOREST RESOURCES AND CONSERVATION

n he recycling of compostedresiduals through forestlands is generally beneficial

because of increased growth oftimber with a low health risk forthe remote human food-chain.Composted waste utilization onforest lands has been documentednationwide and in Florida as anacceptable alternative for wasterecycling (Cole et al., 1986;Riekerk, 1986; Jokela et al.,1990). Recycling the slow-releasematerials carefully and sparinglyon the highly absorptive porousforest soils maintains acceptableecological conditions and runoffwater quality. The added organicmatter increases the absorptivecapacity and decreases the acidityof Florida’s forest soils. Theseprocesses, in turn, increase theretention of heavy metals againstleaching into the water table(Fiske11 and Pritchett, 1979).

Compost Utilization in aSlash Pine PlantationForest

This project built upon aprevious study of the benefits ofcompost application to a slashpine flatwoods site prior toplanting. In that case, compostedMS W application nearly doubledthe yield of wood without mea-surable adverse effects (Jokela etal., 1990). The main objectives of

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the silvicultural municipal solidwaste (MSW) compost utilizationstudy was to investigate the effectsof composting on water-holdingcapacity, soil chemistry, soil/ground water quality, and treesurvival and growth (Riekerk,1995) and to demonstrateconservation of water byincreasing the soil retentioncapacity with amendments oforganic waste products.

The sites were in the AustinCary Memorial Forest near theUniversity of Florida in a clearedarea of sandy soil with a 3 ft deepwater table, and in a six-year oldslash pine ( P i n u s elliottii) planta-tion forest on poorly-drained soil.This site design was chosen toevaluate the effects of leachingdepth on groundwatercontamination, and of weedcompetition on tree survival.

Five-row plots within eachsite received on average a low(59), medium (96), and high (127)dry ton/acre of compost duringthe fall of 1992. Half-length 50 ftplots received 100 lb mixedfertilizer + 100 lb urea +200 lblime (nutrient-only) or 68 dryton/acre wood chips (carbon-only) to separate their combinedeffects in compost. The nutrientapplication with wood chips aver-aged about 50% of the low com-post rate, and that with fertilizer

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thIVERSITY OF FLORIDAGAINESVILLE, FLORIDA

was about 75%. The carbon-to-nitrogen ratio of the compost onthe seedling site was 30, on theforest site 34, and of wood chips58, while the moisture contentswere 33%, 26% and 45%, respec-tively. The urea had 46% nitrogen,the lime 28% calcium, and themixed fertilizer 10% each ofnitrogen, phosphorus andpotassium. The compost on thecleared site was disked into thesoil and then planted with slashpine seedlings, but that on theforested site was only top-dressedbetween tree rows to avoid rootdamage (Figure 14- 1).

Compost, surface soil,soil/ground water sampling andanalysis lasted only for a year, butperiodic tree measurements werecontinued over 5-l / 2 years.

Water-Holding CapacityThe data from the seedling

site indeed showed reduced soilbulk density, which increasedfield soil water content of alltreatments. The high-rate compostapplication significantly increasedsaturated water-holding capacityin the seedling site.

Similar results were reportedfor MSW compost applicationsup to 20 ton/acre in a youngslash pine plantation (Bengstonand Cornette, 1973).


CHAPTER 14: COMPOST USE ON FOREST LANDS

Soil SurFace Chemistry iThe compost treatments i

increased the pH, mineral and ;’organic matter levels, as could be

expected from the relatively highapplication rates. Similar resultshave been reported by others(Fiske11 and Pritchett, 1979;Fiske11 et al., 1979). Post-treat-ment organic matter analyses ;showed a 1.5-2.0 fold increase in iorganic matter for the high corn- /post treatments with up to 3% iorganic matter in the topdressed iforest soil. ..

The wood chips with the high isoluble phosphorus content

....increase the phosphorus in the :.surface soil as much as it was :expected. The high levels of phos- iphorus in percolating soil water i.suggest significant leaching, but :the lack of a treatment response iof the phosphorus level in ground iwater (at both sites) may have ibeen caused by mineral and !biological fixation in the sodic ihorizon (Fiske11 and Pritchett, i.1979).

Soil and Ground WaterQuality

....All treatments increased :

phosphorus levels in soil water of /the seedling site, including a sig- i

nificant rise in phosphorus by thehigh-rate compost. In contrast,the addition of similar rates ofcompost to agricultural soilsunder laboratory conditionsreduced water-extractable phos-phorus levels by fixation (Graetz,1994).

Because of an unexpectedlyhigh phosphorus level in soilwater from the control plot of theforest site, significantly increasedphosphorus levels could not bedemonstrated for the treatments.However, the phosphorus level insoil water from the control of anearlier study on the site was about0.24 ppm (Burger, 1979) suggest-ing significant increases by thetreatments.

The highly variable nutrientlevels of soil water were increasedmostly by an initial flushingeffect, with the exception ofnitrate-nitrogen in the high-ratecompost and wood chip plots ofthe seedling site. A comparison ofthe average nitrate-nitrogen levelsin water-extracts with those in soilwater showed much lower ratiosunder compost than wood chips,suggesting nitrification of thelarge amount of water-solubleammonium-nitrogen in the com-post. Denitrification apparently

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reduced nitrate-nitrogen levelsunder the wet, organic-rich andneutral pH levels of the high-ratecompost, but significant nitrogenimmobilization may have beenthe dominant process under thewood chips with a very high car-bon/nitrogen ratio of 58 (Graetz,1994). The relatively low nitratenitrogen level in soil water underwood chips of the forest site alsosuggested nitrogen immobiliza-tion, but nitrification is low in theacid soil of this site (Burger,1979).

The high pH and conductivi-ty levels under the compost layerswere generated by the significant-ly increased amounts of potassi-um and calcium in soil water,which in turn were exceeded bythose of water-soluble laboratorycompost extracts. The soil/ground water ratio for copper(Cu) was similar to that in aloamy soil column leaching studywhere the process of Cu mobilitywas associated with the solubleCu supply from compost ratherthan being complexed by dis-solved organic matter that wastrapped by the subsoil(Giusquiani et al., 1992).

The chemistry of soil watermay be important for treenutrition; however, that of groundwater is of environmentalconcern. While soil water underall the compost treatments hadhigher levels of nutrient elementsthan the control, only the high-rate compost applicationgenerated ground water qualitylevels that exceeded acceptedstandards for a significant timeinterval. The main contaminantwas nitrate-nitrogen, as wasexpected from its ionic mobilityand its documentation byprevious studies (Riekerk, 1986).

Tree Survival and GrowthThe addition of nutrient-rich

MSW compost obviously has afertilizer effect on plant growth.


CHAPTER 14: COMPOST USE ON FOREST LANDS

The effect of compost on average- i.tree volume was a 42% increase iby high, 33% by medium and i25% by low applications, while ithat by wood chips was 33% and !fertilizer was 29% after 66 imonths. The latter responses sug- igest that about half of the corn- ipost effect was derived from the iadded organic matter (water-hold-ing capacity) and half fromimproved nutrition. Treemortality in the fertilizer plotcreated a plot volume 63% higherthan that of the control while theothers grouped around 37% more.This compares to about 70 per- icent of biomass weight after 16 iyears in an earlier study, which is ;in part due to increased wood /

density with age (Jokela et al.,1990).

Recommendations forCompost Application onForest Lands

The information from thisstudy suggests that for a large-scale application, better methodsare required for a more evendistribution of the compost overthe site. Top dressing in anexisting pine plantation is feasiblewith a straight-walled live-bottomwagon, but incorporation maydamage the roots. Application ofpaper-mill sludge pellets with acentrifugal fertilizer spreader hasbeen done operationally innortheast Florida.

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Compost application rates fortree growth improvement can beas high as 130 dry ton/acre, buttransport and application costsand increased tree mortalitymakes a medium rate of 100 dryton/acre more effective. Inaddition, established limits ofenvironmental water qualitystandards in Florida restrict theapplication rate for poorly-drained sandy pine flatwoods to400 lbs/acre of nitrogen per year,or about 100 dry ton/acre ofcompost every five years. Earliertrials in a plantation establish-ment showed that optimal growthcould be realized at 100 tons/acreor less. 0



Reclamation of PhosphateMine lands with CompostThe phosphate mining industry annually reclaims anaverage of 4,000 to 5,000 acres of mine lands in Florida,making it a viable market for compost products.

Jm RAGSDALE

SANITATION DEPARTMENT

CITY OF ST. PETERSBURG

ST. PETERSBURG , FLORIDA

n he phosphate industry in iFlorida produces more than i75 percent of the United i

States’ supply of phosphate. The iindustry is concentrated in five isouthwest Florida counties that iinclude Hillsborough, Polk,Hardee, Manatee and Desoto,where over 90 percent ofFlorida’s phosphate is mined. In i1996, the mining industry began i.reclamation at a 100 percent :equivalency that requires one acreto be reclaimed for every acremined. The phosphate miningindustry on average reclaimsbetween 4,000 and 5,000 acres ayear of mine lands in Florida.

Statutory and EconomicConsiderations

The cost to reclaim phos- iphate land is between $3,000 and i$8,000 per acre. Earth-moving icontributes the largest single iexpense. Mining reclamation icosts for “old-lands” - those imined before July 1, 1975 - are i.subsidized by the State

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Comptroller from the Minerals !Trust Fund, which is funded by a iphosphate severance tax. After i.that date, state statutes required /mandatory reclamation of mine ilands by the phosphate industry i..itself. ....

The Comptroller reimburses ithe industry for reclamation of /.

the old lands at a rate of $4,000an acre for mined-out areas and$2,500 an acre for clay settling i:areas and other land forms. Of ithe 87,000 acres of old landsmined before 1975, almost halfremain to be reclaimed.

Traditional Use of OrganicMaterial by the MiningIndustry

In Florida, the level oforganic matter required by the :Department of Transportation for !.establishment of vegetation is 1 !percent. Soil found on mined iphosphate lands usually has less ithan one half of one percent !organic matter. The mining indus- itry manages its soil to recover its ;organic content. Topsoil found in /overburden is set aside for future :use. Peat is seldom available.Muck is the primary materialused, but its availability varies.Muck is found in wetland areaswith depths ranging from a few [centimeters to several meters. As ipart of a permit to mine wetlands, imining companies typically are :required to remove and stockpile imuck prior to mining and to use /.it later to reclaim wetlands.

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At the present time, the pri- i.mary reclamation activity where iorganic material may be required :is in the re-creation of wetlands. /The main reasons to save muck

found on phosphate lands are itsability to provide a low costsource of wetland seeds for plantestablishment and its ability toretain moisture during the dryseason.

Some of the problemsexperienced by the industry withthe mining of muck are: 1) it isnot uniform in particle size, 2) itmay contain nuisance plant seeds,3) while stockpiled, its moisturelevel should be maintained topreserve seed and to avoid winddisbursement, and 4) muck maybe found with a relatively loworganic content level (around 20percent .)

Wetland creation involves theadditional expense of soilrecontouring of elevation tocreate hydrological conditionsneeded to form wetlands. Anotherassociated cost to the mine com-pany is the processing of muckthat includes excavation, transfer,stockpiling and application.

Blending of recycled urbanplant debris with muck in order toobtain biological diversity of seedis one option for future field trials.To use recycled urban plant debrisorganic material in wetlands miti-gation projects, it should have thefollowing parameters: 1) be free ofweed seed, 2) have a preferred pHrange between 5.0 to 6.3) containa particle size that will not float,


CHAPTER 15: RECLAMATION OF PHOSPHATE MINE LAND WITH COMPOST

4) have a level of maturity thatreleases nitrogen, 5) have anorganic content range between35 and 65 percent.

Mining Industry% Past andPresent Use of RecycledOrganic Material

The industry has had limitedexposure to the use of urbanplant debris organic material.Historically, there have been a fewsmall scale field experimentswhere urban plant debris organicmaterial was used in demonstra-tion projects. It has been used inturf establishment on quartz sandslopes and on phosphogypsumstacks.

The industry now requiresthat organic material be particlesize-reduced, managed for weedseed and delivered by motorcarrier to the reclamation site.Mining activity in Florida islocated on the northern edge ofthe southern climate zone, whichis subject to invasive, nuisanceplants. For this reason, a weedseed-free material is required.Another concern by the industryis the availability of a sufficientquantity of acceptable material tomeet its reclamation needs.

The Industry’s Conversionto the Use of RecycledOrganic Material

The most important indicatorof successful reclamation is plantperformance. State regulationsallow one year for revegetationand one year for vegetativeestablishment. Soil that has beenmined needs improvement tosupport vegetation. Addition oforganic material results inincreased soil fertility and theability of vegetation to becomeestablished and self-sustaining.The use of recycled urban plantdebris organic material by thephosphate industry will increasefollowing successful demonstra-

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tion projects. The industry is nowexploring the development of alow cost means of land applica-tion of organic material that doesnot exceed its present reclamationcosts per acre.

Future Uses and Benefitsof Recycled Yard WasteOrganic Material

The lands with the greatestpotential for use of urban plantdebris organic material as a soilamendment are the more sterileupland areas that receive sandtailings and the clay settling areas,where the organic content is lessthan one half of one percent. Thesuccessful establishment of turf inupland areas acts as a buffer to fil-ter storm water runoff thatreduces water turbidity in wet-lands. Organic material also canbe substituted for the applicationof clay that is placed in sand,where it is used to improve thecation-exchange capacity andmoisture retention.

The establishment ofvegetation aided by the use oforganic material will improve theproperties of soil structure andreduce soil erosion. The additionof organic material aids the soil’sphysical and chemical propertiesby improving cation-exchangecapacity, increasing water-holdingcapacity, reducing the acidity insoils, and providing plant nutri-ents. Soil biological properties areimproved by reintroduction of amicrobial population in the soil.

Sheet cornposting. Stateregulations regarding the durationof time allowed for completion ofreclamation is determined by thesize of the land and the characterof the soil. On a 400-acre tract ofland, the state normally allows atotal of six years, including fouryears for earth-moving, one yearfor revegetation and one year forplant establishment. A longerreclamation period is allowed forupland soils that contain sand

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tailings and clay settling.Sheet cornposting offers a

large-scale processing potentialbut requires, as a precondition,the availability of a large tract ofland and ample time. The sheetcornposting process involves theformation of windrows withspecially designed delivery trailerscontaining live bottoms. Thewindrows are strategicallypositioned for the future evendistribution of material whenspread to a depth of one or twofeet over large land areas. Attwo feet of depth, the sheetcornposting process acceleratesdecomposition by creating alower temperature than found inwindrows. This provides abroader range of microbialactivity while improving the avail-ability of oxygen and retainingrain water that accumulates onthe bottom six inches. At a futuredate, the remainder of the decom-posed material is cut into the soilprior to plant revegetation.

The significance of the scaleof operation is illustrated by thefact that, at two feet of depth, anacre will hold 1,000 tons and a100-acre tract will hold 100,000tons.

Sand dam. The phosphateindustry has reduced its depen-dence on deep well water andnow relies heavily on recyclingthe water used to transport theslurry mix of mined ore. It alsouses water as a medium toseparate non-phosphate material.Quartz sand is removed from thematrix of ore material and is usedto construct dams found in anelaborate network of retentionlakes and canals used to removeclay and reuse the water.

Quartz sand is low innutrients and organic matter andhas poor water retention qualities.To comply with the requirementsof turf establishment on damsconstructed of sand, the industryapplies a mixture of bahia and


CHAPTER 15: RECLAMATION OF PHOSPHATE MINE LAND WITH COMPOST

bermuda seed to the dam facewall. The industry reports that,within three years, sympatheticweed growth inundates the seededareas. Contributing to thiscondition is the four-to-one slopeof the dam and the mid-rangesize of the quartz sand particlethat allows water to percolate,creating arid conditions for turfestablishment.

The industry is interested inexperimenting in a field trial overa two-acre area of a sand damface. Urban plant debris organicmaterial will be blended with thesand at 0, 30 and 50 percentratios and applied to one footdepth. The year-long demonstra-tion project will attempt to showthat, as the material decomposes,it will provide moisture and nutri-ent retention needed to assureextended turf establishment, help-

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ing to further stabilize the slope.Phosphogypsum stacks. This

is another area where the miningindustry may be able to use largeamounts of urban plant debrisorganic material. Very littleresearch is available using urbanplant debris as a medium amend-ed on slopes. Here the objective isto create soil conditions thatimprove the establishment andsurvival of turf grass on phospho-gypsum stacks and that helpremediate the effluence impact ofsurface water runoff that mayinclude soluble salts, fluoride andradon.

The establishment of turf ongypsum stacks has proven difficultas a result of a very acidic pHrange between 3.0 and 5.0.Composted urban plant debrisorganic material with a higher pHrange of around 8.0 is expected to

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raise the soil pH while alsoimproving moisture and nutrientretention qualities to the soil.

Roadway stabilization.Phosphate mines use longpipeline routes to transport themined ore slurry to benefactionplants where the phosphate rockis separated. The pipelines requireservice roads and the routes crossareas high in sand content. Yardwaste organic material provides atemporary stabilization materialfor the road surface whileproviding texture to the sand andreducing dust.

Erosion control. There arewatershed areas from rainfall thaterode upland areas. Recycledurban plant debris mulch hasbeen effective in reducing erosionwhen placed in a row or smallberm across the top of the areasubject to erosion in upland areas. 0


GLOSSARY

Biosolids: The solid material /removed from wastewater afterdomestic sewage has beenprocessed at wastewater treatment [plants. Also known as “residuals” [or “sewage sludge” (adapted from ;Biosolids Management in Florida, !.1997).

....

Compost: “Solid waste that has i.undergone biological decomposi- /tion of organic matter, has been idisinfected using cornposting or isimilar technologies, and has been :stabilized to a degree which is ;potentially beneficial to plant i..growth and which is used or sold i.for use as a soil amendment, arti- ificial top soil, growing medium i.amendment or other similar uses” i(Rule 62-701.200(21), Fla.Administrative Code).

Contamination: Unwantedmaterial. Physical contaminantscan include sharps, metalfragments, glass, plastic, andstones; chemical contaminantscan include trace heavy metalsand toxic organic compounds;biological contaminants caninclude pathogens. In excessiveamounts, a contaminant canbecome a pollutant (adapted fromCornposting Council, 1994).

Curing: The last stage ofcornposting that occurs aftermost of the readily metabolizedmaterial has been decomposed orstabilized. It provides additionalbiological stabilization(Cornposting Council, 1994).

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.Feedstock: Organic materials that ;can be composted. Commonly- iused feedstocks include grass :clippings and other urban plant ;debris, biosolids and municipal isolid waste.

.

Heavy Metals: A group ofmetallic elements with

concentrations that are regulated ibecause of the potential for itoxicity to humans, animals, or /plants. Trace elements include i.copper, nickel, cadmium, lead, imercury, and zinc if present in iexcessive amounts (Cornposting /Council, 1994).

Humus: A complex amorphous i.aggregate, formed during the i.microbial decomposition oralteration of plant or animal iresidues and products synthesized ;by soil organisms; principal con- i.stituents are derived of lignins, jproteins, and cellulose combined :with inorganic soil constituents; [dark or black carbon-rich ....relatively stable residue resulting ifrom the decomposition of :organic matter (Cornposting .Council, 1994). .....

Macronutrients: Nutrients usedby plants in high quantities.

Mature Compost: Material that :has gone through the windrow or i.in-vessel process for “sanitation” iand has been sufficiently cured for !.stability so as not to introduce iphytotoxic acids. Mature compost /will not deplete soil nitrogen to isupport additional biological idecomposition but will be ibeneficial to soil and plants !grown in the amended soil !(adapted from Cornposting !Council, 1994).

M i c r o n u t r i e n t s : Nut r i en t s !required by plants in small

;...quantities but toxic at high levels, i.including boron, chlorine, copper, !iron, manganese, molybdenum, iand zinc.

....

Mulch: A soil surface cover used i.to retain moisture by retarding :evaporation, discourage weed /growth, stabilize temperatures by !insulating the soil, and stabilize [

the soil against erosion from rain-fall (adapted from CornpostingCouncil, 1994).

Nitrogen Immobilization(N-rob): A condition in whichmicroorganisms in immaturecompost consume the availableplant nitrogen in the soil todecompose the compost.Allowing the compost to stabilizefor a few months before plantingor applying nitrogen as a mineralfertilizer usually corrects theproblem.

Organic Matter: Any carbona-ceous material (exclusive ofcarbonates) of animal orvegetable origin, large or small,dead or alive, consisting of hydro-carbons and their derivatives.

Pathogens: Organisms or micro-organisms, including bacteria,mold, fungus, virus, and protozoacapable of producing an infectionor disease in a susceptible host.Measures to control pathogensinclude industrial hygiene,effective design and operationfor biodegradation of pathogennutrients and adequate anduniform aeration and tempera-ture/time to assure pathogendestruction (adapted fromCornposting Council, 1994).

Phytotoxins: Toxins that mayendanger plant viability orfunctionality. (CornpostingCouncil, 1994).

Screening: A production step tomechanically classify materials bysize through the use of screeningequipment.

Soil Conditioner: (SoilAmendment) A soil supplementthat physically stabilizes the soil,improves resistance to erosion,increases permeability to air and


water, improves texture andresistance to crusting, easescultivation, or otherwise improvessoil physical quality (CornpostingCouncil, 1994).

i the soil and can cause nitrogeni deficiency in the soil mix and bei detrimental to plant growth, eveni causing death of plants in some.i cases (Cornposting Council,.; 1994).

Stability: A level of biologicalactivity in a moist, warm, andaerated biomass sample. Unstablebiomass consumes nitrogen andoxygen to support biologicalactivity and generates heat,carbon dioxide, and water vapor.Unstable, active compostdemands nitrogen if applied to

! Urban plant debris: Grass.i clippings and other yard.; trimmings.

i Water Table: The upper surface.i of ground water (Cornpostingi Council, 1994).

i Windrow: An elongated.i formation of urban plant debris.i where the dimension ofi construction, the particle size,; and the manner of rotationi provides a state to control; temperatures. Windrows have ai large exposed surface area whichi encourages passive aeration andi drying.


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