sustainable soil management

ATTRA is the national sustainable agriculture information service operated by the National Centerfor Appropriate Technology, through a grant from the Rural Business-Cooperative Service, U.S.Department of Agriculture. These organizations do not recommend or endorse products,companies, or individuals. NCAT has offices in Fayetteville, Arkansas (P.O. Box 3657, Fayetteville,AR 72702), Butte, Montana, and Davis, California.

National Sustainable Agriculture Information Servicewww.attra.ncat.org

By Preston SullivanNCAT Agriculture SpecialistMay 2004

SOIL SYSTEMS GUIDE

Abstract: This publication covers basic soil properties and management steps toward building and maintaininghealthy soils. Part I deals with basic soil principles and provides an understanding of living soils and how they work.In this section you will find answers to why soil organisms and organic matter are important. Part II covers manage-ment steps to build soil quality on your farm. The last section looks at farmers who have successfully built up their soil.The publication concludes with a large resource section of other available information.

SSSSSUSTUSTUSTUSTUSTAINABLEAINABLEAINABLEAINABLEAINABLE S S S S SOILOILOILOILOIL

MMMMMANAGEMENTANAGEMENTANAGEMENTANAGEMENTANAGEMENT

©2004 NCAT

Table of Contents

Part I. Characteristics ofSustainable Soils ....................................... 2

Introduction ................................................. 2The Living Soil: Texture and Structure ............................................ 2The Living Soil: The Importance of

Soil Organisms.......................................... 3Organic Matter, Humus, and the Soil

Foodweb .................................................... 7Soil Tilth and Organic Matter ................... 8Tillage, Organic Matter, and Plant

Productivity ........................................... 10Fertilizer Amendments and

Biologically Active Soils ....................... 13Conventional Fertilizers .......................... 14Top$oil � Your Farm�$ Capital .............. 15Summary of Part I .................................... 18Summary of Sustainable

Soil Management Principles ............... 19Part II. Management Steps to

Improve Soil Quality ............................ 20Part III. Examples of Successful

Soil Builders (Farmer Profiles) ............ 25References .................................................. 27Additional Resources .............................. 28 Soybeans no-till planted into wheat stubble.

Photo by Preston Sullivan

mailto:[email protected].?subject=Sustainable Soil Management

//SUSTAINABLE SOIL MANAGEMENTPAGE 2

IntroductionIntroductionIntroductionIntroductionIntroduction

What are some features of good soil? Anyfarmer will tell you that a good soil:

� feels soft and crumbles easily� drains well and warms up quickly in

the spring� does not crust after planting� soaks up heavy rains with little runoff� stores moisture for drought periods� has few clods and no hardpan� resists erosion and nutrient loss� supports high populations of soil

organisms� has a rich, earthy smell� does not require increasing inputs for

high yields� produces healthy, high-quality crops

(1)

All these criteria indicate a soil that functionseffectively today and will continue to producecrops long into the future. These characteris-tics can be created through management prac-tices that optimize the processes found in na-tive soils.

How does soil in its native condition function?How do forests and native grasslands produceplants and animals in the complete absence offertilizer and tillage? Understanding the prin-ciples by which native soils function can helpfarmers develop and maintain productive andprofitable soil both now and for future genera-tions. The soil, the environment, and farm con-dition benefit when the soil�s natural produc-tivity is managed in a sustainable way. Reli-ance on purchased inputs declines year by year,while land value and income potential increase.Some of the things we spend money on can bedone by the natural process itself for little ornothing. Good soil management produces cropsand animals that are healthier, less susceptibleto disease, and more productive. To understandthis better, let�s start with the basics.

The Living Soil: TThe Living Soil: TThe Living Soil: TThe Living Soil: TThe Living Soil: Texturexturexturexturextureeeee

and Structureand Structureand Structureand Structureand Structure

Soils are made up of four basic components:minerals, air, water, and organic matter. Inmost soils, minerals represent around 45% ofthe total volume, water and air about 25% each,and organic matter from 2% to 5%. The min-eral portion consists of three distinct particlesizes classified as sand, silt, or clay. Sand is thelargest particle that can be considered soil.

Sand is largely the mineral quartz, though otherminerals are also present. Quartz contains noplant nutrients, and sand cannot hold nutri-ents�they leach out easily with rainfall. Siltparticles are much smaller than sand, but likesand, silt is mostly quartz. The smallest of allthe soil particles is clay. Clays are quite differ-ent from sand or silt, and most types of claycontain appreciable amounts of plant nutrients.Clay has a large surface area resulting from theplate-like shape of the individual particles.Sandy soils are less productive than silts, whilesoils containing clay are the most productive anduse fertilizers most effectively.

Soil texture refers to the relative proportions ofsand, silt, and clay. A loam soil contains thesethree types of soil particles in roughly equal pro-portions. A sandy loam is a mixture containinga larger amount of sand and a smaller amountof clay, while a clay loam contains a largeramount of clay and a smaller amount of sand.These and other texture designations are listedin Table 1.

Another soil characteristic�soil structure�isdistinct from soil texture. Structure refers to theclumping together or �aggregation� of sand, silt,and clay particles into larger secondary clusters.

Sustainable: capable of being maintained atlength without interruption, weakening, orlosing in power or quality.

PART I. Characteristics of SUSTAINABLE SOILS

//SUSTAINABLE SOIL MANAGEMENT PAGE 3

If you grab a handful of soil, good structure isapparent when the soil crumbles easily in yourhand. This is an indication that the sand, silt,and clay particles are aggregated into granulesor crumbs.

Both texture and structure determine pore spacefor air and water circulation, erosion resistance,looseness, ease of tillage, and root penetration.While texture is related to the minerals in thesoil and does not change with agricultural ac-tivities, structure can be improved or destroyedreadily by choice and timing of farm practices.

The Living Soil: TheThe Living Soil: TheThe Living Soil: TheThe Living Soil: TheThe Living Soil: TheImportance of SoilImportance of SoilImportance of SoilImportance of SoilImportance of Soil

OrganismsOrganismsOrganismsOrganismsOrganisms

An acre of living topsoil contains approximately900 pounds of earthworms, 2,400 pounds offungi, 1,500 pounds of bacteria, 133 pounds ofprotozoa, 890 pounds of arthropods and algae,and even small mammals in some cases (2).Therefore, the soil can be viewed as a living com-munity rather than an inert body. Soil organicmatter also contains dead organisms, plantmatter, and other organic materials in variousphases of decomposition. Humus, the dark-col-ored organic material in the final stages of de-composition, is relatively stable. Both organicmatter and humus serve as reservoirs of plantnutrients; they also help to build soil structureand provide other benefits.

The type of healthy living soil required to sup-port humans now and far into the future will

be balanced in nutrients and high in humus,with a broad diversity of soil organisms. It willproduce healthy plants with minimal weed, dis-ease, and insect pressure. To accomplish this,we need to work with the natural processes andoptimize their functions to sustain our farms.

Considering the natural landscape, you mightwonder how native prairies and forests func-tion in the absence of tillage and fertilizers.These soils are tilled by soil organisms, not bymachinery. They are fertilized too, but the fer-tility is used again and again and never leavesthe site. Native soils are covered with a layer ofplant litter and/or growing plants throughoutthe year. Beneath the surface litter, a rich com-plexity of soil organisms decompose plant resi-due and dead roots, then release their storednutrients slowly over time. In fact, topsoil isthe most biologically diverse part of the earth(3). Soil-dwelling organisms release bound-upminerals, converting them into plant-availableforms that are then taken up by the plants grow-ing on the site. The organisms recycle nutrientsagain and again with the death and decay ofeach new generation of plants.

There are many different types of creatures thatlive on or in the topsoil. Each has a role to play.These organisms will work for the farmer�s ben-efit if we simply manage for their survival. Con-sequently, we may refer to them as soil livestock.While a great variety of organisms contributeto soil fertility, earthworms, arthropods, and thevarious microorganisms merit particular atten-tion.

Earthworms

Earthworm burrows enhance water infiltrationand soil aeration. Fields that are �tilled� byearthworm tunneling can absorb water at a rate4 to 10 times that of fields lacking worm tun-nels (4). This reduces water runoff, rechargesgroundwater, and helps store more soil waterfor dry spells. Vertical earthworm burrows pipeair deeper into the soil, stimulating microbialnutrient cycling at those deeper levels. Whenearthworms are present in high numbers, thetillage provided by their burrows can replacesome expensive tillage work done by machin-ery.

Table 1. Soil texture designationsranging from coarse to fine.

Texture DesignationCoarse-textured

Fine-textured

SandLoamy sandSandy loamFine sandy loamLoamSilty loamSiltSilty clay loamClay loam

Clay


Worms eat dead plant material left on top ofthe soil and redistribute the organic matter andnutrients throughout the topsoil layer. Nutri-ent-rich organic compounds line their tunnels,which may remain in place for years if not dis-turbed. During droughts these tunnels allowfor deep plant root penetration into subsoil re-gions of higher moisture content. In additionto organic matter, worms also consume soil andsoil microbes. The soil clusters they expel fromtheir digestive tracts are known as worm castsor castings. These range from the size of a mus-tard seed to that of a sorghum seed, dependingon the size of the worm.

The soluble nutrient content of worm casts isconsiderably higher than that of the original soil(see Table 2). A good population of earthwormscan process 20,000 pounds of topsoil per year�with turnover rates as high as 200 tons per acrehaving been reported in some exceptional cases(5). Earthworms also secrete a plant growthstimulant. Reported increases in plant growthfollowing earthworm activity may be partiallyattributed to this substance, not just to improvedsoil quality.

Earthworms thrive where there is no tillage.Generally, the less tillage the better, and the shal-lower the tillage the better. Worm numbers canbe reduced by as much as 90% by deep and fre-quent tillage (7). Tillage reduces earthwormpopulations by drying the soil, burying the plantresidue they feed on, and making the soil morelikely to freeze. Tillage also destroys verticalworm burrows and can kill and cut up theworms themselves. Worms are dormant in thehot part of the summer and in the cold of win-ter. Young worms emerge in spring and fall�they are most active just when farmers are likelyto be tilling the soil. Table 3 shows the effect oftillage and cropping practices on earthwormnumbers.

As a rule, earthworm numbers can be increasedby reducing or eliminating tillage (especially falltillage), not using a moldboard plow, reducingresidue particle size (using a straw chopper onthe combine), adding animal manure, and grow-ing green manure crops. It is beneficial to leaveas much surface residue as possible year-round.

Figure 1. The soil is teeming with organisms that cyclenutrients from soil to plant and back again.

Table 2. Selected nutrient analyses ofworm casts compared to those of the sur-rounding soil.Nutrient Worm casts Soil

Lbs/ac Lbs/acCarbon 171,000 78,500Nitrogen 10,720 7,000Phosphorus 280 40Potassium 900 140

From Graff (6). Soil had 4% organic matter.

Table 3. Effect of crop management onearthworm populations.

Crop Management

Corn Plow 1Corn No-till 2Soybean Plow 6Soybean No-till 14Bluegrass/

clover �- 39Dairy

pasture �- 33

Worms/foot2

From Kladivko (8).


Cropping systems that typically have the mostearthworms are (in descending order) perennialcool-season grass grazed rotationally, warm-season perennial grass grazed rotationally, andannual croplands using no-till. Ridge-till andstrip tillage will generally have more earthwormsthan clean tillage involving plowing and disking.Cool season grass rotationally grazed is highestbecause it provides an undisturbed (no-tillage)environment plus abundant organic matter fromthe grass roots and fallen grass litter. Generallyspeaking, worms want their food on top, andthey want to be left alone.

Earthworms prefer a near-neutral soil pH, moistsoil conditions, and plenty of plant residue onthe soil surface. They are sensitive to certainpesticides and some incorporated fertilizers.Carbamate insecticides, including Furadan,Sevin, and Temik, are harmful to earthworms,notes worm biologist Clive Edwards of OhioState University (4). Some insecticides in theorganophosphate family are mildly toxic toearthworms, while synthetic pyrethroids areharmless to them (4). Most herbicides have littleeffect on worms except for the triazines, suchas Atrazine, which are moderately toxic. Also,anhydrous ammonia kills earthworms in theinjection zone because it dries the soil and tem-porarily increases the pH there. High rates ofammonium-based fertilizers are also harmful.

For more information on managing earthworms,order The Farmer�s Earthworm Handbook: Man-aging Your Underground Moneymakers, by DavidErnst. Ernst�s book contains details on whatearthworms need to live, how to increase wormnumbers, the effects of tillage, manure, and live-stock management on earthworms, how 193chemicals affect earthworms, and more. See theAdditional Resources section of this publica-tion for ordering information. Also visit theearthworm Web sites listed in that section.

Arthropods

In addition to earthworms, there are manyother species of soil organisms that can be seenby the naked eye. Among them are sowbugs,

millipedes, centipedes, slugs, snails, and spring-tails. These are the primary decomposers. Theirrole is to eat and shred the large particles of plantand animal residues. Some bury residue, bring-ing it into contact with other soil organisms thatfurther decompose it. Some members of thisgroup prey on smaller soil organisms. Thespringtails are small insects that eat mostly fungi.Their waste is rich in plant nutrients releasedafter other fungi and bacteria decompose it. Alsoof interest are dung beetles, which play a valu-able role in recycling manure and reducing live-stock intestinal parasites and flies.

Bacteria

Bacteria are the most numerous type of soil or-ganism: every gram of soil contains at least amillion of these tiny one-celled organisms. Thereare many different species of bacteria, each withits own role in the soil environment. One of themajor benefits bacteria provide for plants is inmaking nutrients available to them. Some spe-cies release nitrogen, sulfur, phosphorus, andtrace elements from organic matter. Othersbreak down soil minerals, releasing potassium,phosphorus, magnesium, calcium, and iron.Still other species make and release plantgrowth hormones, which stimulate rootgrowth.

Several species of bacteria transform nitrogenfrom a gas in the air to forms available for plantuse, and from these forms back to a gas again.A few species of bacteria fix nitrogen in the rootsof legumes, while others fix nitrogen indepen-dently of plant association. Bacteria are respon-sible for converting nitrogen from ammoniumto nitrate and back again, depending on cer-tain soil conditions. Other benefits to plantsprovided by various species of bacteria includeincreasing the solubility of nutrients, improvingsoil structure, fighting root diseases, and detoxi-fying soil.

Fungi

Fungi come in many different species, sizes, andshapes in soil. Some species appear as thread-like colonies, while others are one-celled yeasts.Slime molds and mushrooms are also fungi.Many fungi aid plants by breaking down or-ganic matter or by releasing nutrients from soil

As a rule, earthworm numbers can be in-creased by reducing or eliminating tillage.


minerals. Fungi are generally quick to colonizelarger pieces of organic matter and begin thedecomposition process. Some fungi produceplant hormones, while others produce antibiot-ics including penicillin. There are even speciesof fungi that trap harmful plant-parasitic nema-todes.

The mycorrhizae (my-cor-ry´-zee) are fungi thatlive either on or in plant roots and act to extendthe reach of root hairs into the soil. Mycorrhizaeincrease the uptake of water and nutrients, es-pecially phosphorus. They are particularly im-portant in degraded or less fertile soils. Rootscolonized by mycorrhizae are less likely to bepenetrated by root-feeding nematodes, since thepest cannot pierce the thick fungal network.Mycorrhizae also produce hormones and anti-biotics that enhance root growth and providedisease suppression. The fungi benefit by tak-ing nutrients and carbohydrates from the plantroots they live in.

Actinomycetes

Actinomycetes (ac-tin-o-my´-cetes) are thread-like bacteria that look like fungi. While not asnumerous as bacteria, they too perform vitalroles in the soil. Like the bacteria, they helpdecompose organic matter into humus, releas-ing nutrients. They also produce antibiotics tofight diseases of roots. Many of these same an-tibiotics are used to treat human dis-eases. Actinomycetes are respon-sible for the sweet, earthy smellnoticed whenever a biologicallyactive soil is tilled.

Algae

Many different species of algae live in the up-per half-inch of the soil. Unlike most other soilorganisms, algae produce their own foodthrough photosynthesis. They appear as agreenish film on the soil surface following a satu-rating rain. Algae improve soil structure by pro-ducing slimy substances that glue soil togetherinto water-stable aggregates. Some species ofalgae (the blue-greens) can fix their own nitro-gen, some of which is later released to plantroots.

Protozoa

Protozoa are free-living microorganisms thatcrawl or swim in the water between soil par-ticles. Many soil protozoa are predatory, eat-ing other microbes. One of the most common isan amoeba that eats bacteria. By eating anddigesting bacteria, protozoa speed up the cy-cling of nitrogen from the bacteria, making itmore available to plants.

Nematodes

Nematodes are abundant in most soils, and onlya few species are harmful to plants. The harm-less species eat decaying plant litter, bacteria,fungi, algae, protozoa, and other nematodes.Like other soil predators, nematodes speed therate of nutrient cycling.

Soil organisms and soil quality

All these organisms�from the tiny bacteria upto the large earthworms and insects�interactwith one another in a multitude of ways in thesoil ecosystem. Organisms not directly involvedin decomposing plant wastes may feed on eachother or each other�s waste products or the othersubstances they release. Among the substancesreleased by the various microbes are vitamins,amino acids, sugars, antibiotics, gums, andwaxes.

Roots can also release into thesoil various substances thatstimulate soil microbes. Thesesubstances serve as food for se-lect organisms. Some scientistsand practitioners theorize that

plants use this means to stimulate the specificpopulation of microorganisms capable of releas-ing or otherwise producing the kind of nutri-tion needed by the plants.

Research on life in the soil has determined thatthere are ideal ratios for certain key organismsin highly productive soils (9). The Soil FoodwebLab, located in Oregon, tests soils and makesfertility recommendations that are based on thisunderstanding. Their goal is to alter the makeup

Research on life in the soil hasdetermined that there areideal ratios for certain key or-ganisms in highly productivesoils.


of the soil microbial community so it resemblesthat of a highly fertile and productive soil. Thereare several different ways to accomplish thisgoal, depending on the situation. For more onthe Soil Foodweb Lab, see the Additional Re-sources section of this publication.

Because we cannot see most of the creatures liv-ing in the soil and may not take time to observethe ones we can see, it is easy to forget aboutthem. See Table 4 for estimates of typicalamounts of various organisms found in fertilesoil. There are many Web sites that provide in-depth information on soil organisms. Look fora list of these Web sites in the Additional Re-sources section. Many of these sites have colorphotographs of soil organisms and describe theirbenefits to soil fertility and plant growth.

OrOrOrOrOrganic Matterganic Matterganic Matterganic Matterganic Matter, Humus,, Humus,, Humus,, Humus,, Humus,and the Soil Foodweband the Soil Foodweband the Soil Foodweband the Soil Foodweband the Soil Foodweb

Understanding the role that soil organisms playis critical to sustainable soil management. Basedon that understanding, focus can be directedtoward strategies that build both the numbersand the diversity of soil organisms. Like cattleand other farm animals, soil livestock requireproper feed. That feed comes in the form oforganic matter.

Organic matter and humus are terms that de-scribe somewhat different but related things.Organic matter refers to the fraction of the soilthat is composed of both living organisms andonce-living residues in various stages of decom-position. Humus is only a small portion of theorganic matter. It is the end product of organicmatter decomposition and is relatively stable.Further decomposition of humus occurs veryslowly in both agricultural and natural settings.In natural systems, a balance is reached be-tween the amount of humus formation and theamount of humus decay (11). This balance alsooccurs in most agricultural soils, but often at amuch lower level of soil humus. Humus con-tributes to well-structured soil that, in turn, pro-duces high-quality plants. It is clear that man-agement of organic matter and humus is essen-tial to sustaining the whole soil ecosystem.

The benefits of a topsoil rich in organic matterand humus are many. They include rapid de-composition of crop residues, granulation of soilinto water-stable aggregates, decreased crust-ing and clodding, improved internal drainage,better water infiltration, and increased waterand nutrient holding capacity. Improvementsin the soil�s physical structure facilitate easiertillage, increased water storage capacity, re-duced erosion, better formation and harvestingof root crops, and deeper, more prolific plantroot systems.

Soil organic matter can be compared to a bankaccount for plant nutrients. Soil containing 4%organic matter in the top seven inches has80,000 pounds of organic matter per acre. That80,000 pounds of organic matter will containabout 5.25% nitrogen, amounting to 4,200pounds of nitrogen per acre. Assuming a 5%release rate during the growing season, the or-ganic matter could supply 210 pounds of nitro-gen to a crop. However, if the organic matter isallowed to degrade and lose nitrogen, pur-chased fertilizer will be necessary to prop upcrop yields.

All the soil organisms mentioned previously,except algae, depend on organic matter as theirfood source. Therefore, to maintain their popu-lations, organic matter must be renewed fromplants growing on the soil, or from animal ma-nure, compost, or other materials imported from

Table 4. Weights of soil organisms in thetop 7 inches of fertile soil.

Bacteria 1000Actinomycetes 1000Molds 2000Algae 100Protozoa 200Nematodes 50Insects 100Worms 1000Plant roots 2000

Organism Pounds of liveweight/acre

From Bollen (10).

Like cattle and other farm animals, soil live-stock require proper feed.


off site. When soil livestock arefed, fertility is built up in the soil,and the soil will feed the plants.

Ultimately, building organic mat-ter and humus levels in the soil isa matter of managing the soil�sliving organisms�something akin to wildlifemanagement or animal husbandry. This entailsworking to maintain favorable conditions ofmoisture, temperature, nutrients, pH, and aera-tion. It also involves providing a steady foodsource of raw organic material.

Soil Tilth and OrganicSoil Tilth and OrganicSoil Tilth and OrganicSoil Tilth and OrganicSoil Tilth and OrganicMatterMatterMatterMatterMatter

A soil that drains well, does not crust, takes inwater rapidly, and does not make clods is saidto have good tilth. Tilth is the physical condi-tion of the soil as it relates to tillage ease, seed-bed quality, easy seedling emergence, and deeproot penetration. Good tilth is dependent onaggregation�the process whereby individualsoil particles are joined into clusters or �aggre-gates.�

Aggregates form in soils when individual soilparticles are oriented and brought togetherthrough the physical forces of wetting and dry-ing or freezing and thawing. Weak electricalforces from calcium and magnesium hold soilparticles together when the soil dries. When

these aggregates become wetagain, however, their stabilityis challenged, and they maybreak apart. Aggregates canalso be held together by plantroots, earthworm activity, andby glue-like products pro-

duced by soil microorganisms. Earthworm-cre-ated aggregates are stable once they come outof the worm. An aggregate formed by physicalforces can be bound together by fine root hairsor threads produced by fungi.

Aggregates can also become stabilized (remainintact when wet) through the by-products oforganic matter decomposition by fungi and bac-teria�chiefly gums, waxes, and other glue-likesubstances. These by-products cement the soilparticles together, forming water-stable aggre-gates (Figure 2). The aggregate is then strongenough to hold together when wet�hence theterm �water-stable.�

USDA soil microbiologist Sara Wright namedthe glue that holds aggregates together�glomalin� after the Glomales group of commonroot-dwelling fungi (12). These fungi secrete agooey protein known as glomalin through theirhair-like filaments, or hyphae. When Wrightmeasured glomalin in soil aggregates she foundlevels as high as 2% of their total weight in east-ern U.S. soils. Soil aggregates from the Westand Midwest had lower levels of glomalin. Shefound that tillage tends to lower glomalin lev-els. Glomalin levels and aggregation were

Ultimately, building organicmatter and humus in the soilis a matter of managing thesoil�s living organisms.

Figure 2. Microbial byproducts glue soil particles into water-stable aggregates.

MICROBIAL AND FUNGAL BYPRODUCTS GLUE

THE PARTICLES TOGETHER

DISPERSED STATE AGGREGATED STATE


higher in no-till corn plots than in tilled plots(12). Wright has a brochure describing glomalinand how it benefits soil, entitled Glomalin, a Man-ageable Soil Glue. To order this brochure see theAdditional Resources section of this publica-tion.

A well-aggregated soil allows for increasedwater entry, increased air flow, and increasedwater-holding capacity (13). Plant roots occupya larger volume of well-aggregated soil, high inorganic matter, as compared to a finely pulver-ized and dispersed soil, low in organic matter.Roots, earthworms, and soil arthropods canpass more easily through a well-aggregated soil(14). Aggregated soils also prevent crusting ofthe soil surface. Finally, well-aggregated soilsare more erosion resistant, because aggregatesare much heavier than their particle compo-nents. For a good example of the effect of or-ganic matter additions on aggregation, asshown by subsequent increase in water entryinto the soil, see Table 5.

The opposite of aggregation is dispersion. In adispersed soil, each individual soil particle is freeto blow away with the wind or wash awaywith overland flow of water.

Clay soils with poor aggregation tend to besticky when wet, and cloddy when dry. If theclay particles in these soils can be aggregatedtogether, better aeration and water infiltrationwill result. Sandy soils can benefit from aggre-gation by having a small amount of dispersedclay that tends to stick between the sand par-ticles and slow the downward movement ofwater.

Crusting is a common problem on soils that arepoorly aggregated. Crusting results chiefly fromthe impact of falling raindrops. Rainfall causesclay particles on the soil surface to disperse and

clog the pores immediately beneath the surface.Following drying, a sealed soil surface resultsin which most of the pore space has been dras-tically reduced due to clogging from dispersedclay particles. Subsequent rainfall is much morelikely to run off than to flow into the soil (Fig-ure 3).

Since raindrops start crusting, any managementpractices that protect the soil from their impactwill decrease crusting and increase water flowinto the soil. Mulches and cover crops serve thispurpose well, as do no-till practices, which al-low the accumulation of surface residue. Also,a well-aggregated soil will resist crusting be-cause the water-stable aggregates are less likelyto break apart when a raindrop hits them.

Long-term grass production produces the best-aggregated soils (16). A grass sod extends amass of fine roots throughout the topsoil, con-

air water

Crusted

air water

Well-Aggregated

Figure 3. Effects of aggregation on water and airentry into the soil.Derived from Land Stewardship ProjectMonitoring Toolbox (15).

Table 5. Water entry into the soil after 1hourManure Rate (tons/acre) Inches of water

0 1.2 8 1.9 16 2.7

Boyle et al. (13).


tributing to the physical processes that help formaggregates. Roots continually remove waterfrom soil microsites, providing local wetting anddrying effects that promote aggregation. Fineroot hairs also bind soil aggregates together.

Roots also produce food for soilmicroorganisms and earth-worms, which in turn generatecompounds that bind soil par-ticles into water-stable aggre-gates. In addition, perennialgrass sods provide protectionfrom raindrops and erosion. Thus, a perennialcover creates a combination of conditions opti-mal for the creation and maintenance of well-aggregated soil.

Conversely, cropping sequences that involveannual plants and extensive cultivation provideless vegetative cover and organic matter, andusually result in a rapid decline in soil aggrega-tion. For more information on aggregation, seethe soil quality information sheet entitled Ag-gregate Stability at the Soil Quality Institute�shome page, <http://soils.usda.gov/sqi/files/sq_eig_1.pdf>. From there, click on Soil Qual-ity Information Sheets, then click on AggregateStability.

Farming practices can be geared to conserve andpromote soil aggregation. Because the bindingsubstances are themselves susceptible to micro-bial degradation, organic matter needs to bereplenished to maintain microbial populationsand overall aggregated soil status. Practicesshould conserve aggregates once they areformed, by minimizing factors that degrade anddestroy aggregation. Some factors that destroyor degrade soil aggregates are:

� bare soil surface exposed to the impact ofraindrops

� removal of organic matter through crop pro-duction and harvest without return of or-ganic matter to the soil

� excessive tillage� working the soil when it is too wet or too

dry� use of anhydrous ammonia, which speeds

up decomposition of organic matter� excess nitrogen fertilization

� allowing the build-up of excess sodium fromirrigation or sodium-containing fertilizers

TTTTTillage, Orillage, Orillage, Orillage, Orillage, Organic Matterganic Matterganic Matterganic Matterganic Matter, and, and, and, and, andPlant ProductivityPlant ProductivityPlant ProductivityPlant ProductivityPlant Productivity

Several factors affect the levelof organic matter that can bemaintained in a soil. Amongthese are organic matter addi-tions, moisture, temperature,

tillage, nitrogen levels, cropping, and fertiliza-tion. The level of organic matter present in thesoil is a direct function of how much organicmaterial is being produced or added to the soilversus the rate of decomposition. Achieving thisbalance entails slowing the speed of organic mat-ter decomposition, while increasing the supplyof organic materials produced on site and/oradded from off site.

Moisture and temperature also profoundly af-fect soil organic matter levels. High rainfall andtemperature promote rapid plant growth, butthese conditions are also favorable to rapid or-ganic matter decomposition and loss. Low rain-fall or low temperatures slow both plant growthand organic matter decomposition. The nativeMidwest prairie soils originally had a highamount of organic matter from the continuousgrowth and decomposition of perennial grasses,combined with a moderate temperature that didnot allow for rapid decomposition of organicmatter. Moist and hot tropical areas may ap-pear lush because of rapid plant growth, butsoils in these areas are low in nutrients. Rapiddecomposition of organic matter returns nutri-ents back to the soil, where they are almost im-mediately taken up by rapidly growing plants.

Tillage can be beneficial or harmful to a biologi-cally active soil, depending on what type of till-age is used and when it is done. Tillage affectsboth erosion rates and soil organic matter de-composition rates. Tillage can reduce the or-ganic matter level in croplands below 1%, ren-dering them biologically dead. Clean tillage in-volving moldboard plowing and disking breaksdown soil aggregates and leaves the soil proneto erosion from wind and water. The mold-board plow can bury crop residue and topsoilto a depth of 14 inches. At this depth, the oxy-

The best-aggregated soils arethose that have been in long-term grass production.

http://soils.usda.gov/sqi/files/sq_eig_1.pdf

http://soils.usda.gov/sqi/files/sq_eig_1.pdf


gen level in the soil is so low that decomposi-tion cannot proceed adequately. Surface-dwell-ing decomposer organisms suddenly find them-selves suffocated and soon die. Crop residuesthat were originally on the surface but now havebeen turned under will putrefy in the oxygen-deprived zone. This rotting activity may give aputrid smell to the soil. Furthermore, the topfew inches of the field are now often coveredwith subsoil having very little organic mattercontent and, therefore, limited ability to supportproductive crop growth.

The topsoil is where the biological activity hap-pens�it�s where the oxygen is. That�s why afence post rots off at the surface. In terms oforganic matter, tillage is similar to opening theair vents on a wood-burning stove; adding or-ganic matter is like adding wood to the stove.Ideally, organic matter decomposition shouldproceed as an efficient burn of the �wood� torelease nutrients and carbohydrates to the soilorganisms and create stable humus. Shallowtillage incorporates residue and speeds the de-composition of organic matter by adding oxy-gen that microbes need to become more active.

In cold climates with a long dormant season,light tillage of a heavy residue may be benefi-cial; in warmer climates it is hard enough tomaintain organic matter levels without any till-age.

As indicated in Figure 4, moldboard plowingcauses the fastest decline of organic matter, no-till the least. The plow lays the soil up on itsside, increasing the surface area exposed to oxy-gen. The other three types of tillage are inter-mediate in their ability to foster organic matterdecomposition. Oxygen is the key factor here.The moldboard plow increases the soil surfacearea, allowing more air into the soil and speed-ing the decomposition rate. The horizontal lineon Figure 4 represents the replenishment of or-ganic matter provided by wheat stubble. Withthe moldboard plow, more than the entire or-ganic matter contribution from the wheat strawis gone within only 19 days following tillage.Finally, the passage of heavy equipment in-creases compaction in the wheel tracks, andsome tillage implements themselves compact thesoil further, removing oxygen and increasing thechance that deeply buried residues will putrefy.

Organic Matter loss 19 days after Tillage

Poun

ds/a

c O

M lo

ss

4000

3500

3000

2500

2000

1500

1000

500 0

Reicosky & Lindstrom, 1995

Residue from wheat crop

Mb. plow Mb.+ 2 disc

Disc Chisel Pl. No-till

Tillage type

Figure 4. Organic matter losses after various tillage practices (17).


Tillage also reduces the rate of water entry intothe soil by removal of ground cover and destruc-tion of aggregates, resulting in compaction andcrusting. Table 6 shows three different tillagemethods and how they affect water entry intothe soil. Notice the direct relationship betweentillage type, ground cover, and water infiltra-tion. No-till has more than three times the wa-ter infiltration of the moldboard-plowed soil.Additionally, no-till fields will have higher ag-gregation from the organic matter decomposi-tion on site. The surface mulch typical of no-tillfields acts as a protective skin for the soil. Thissoil skin reduces the impact of raindrops andbuffers the soil from temperature extremes aswell as reducing water evaporation.

Both no-till and reduced-tillage systems providebenefits to the soil. The advantages of a no-tillsystem include superior soil conservation, mois-ture conservation, reduced water runoff, long-term buildup of organic matter, and increasedwater infiltration. A soil managed without till-age relies on soil organisms to take over the jobof plant residue incorporation formerly done bytillage. On the down side, no-till can foster areliance on herbicides to control weeds and canlead to soil compaction from the traffic of heavyequipment.

Pioneering development work on chemical-freeno-till farming is proceeding at several researchstations and farms in the eastern U.S. Pennsyl-vania farmer Steve Groff has been farming no-till with minimal or no herbicides for severalyears. Groff grows cover crops extensively inhis fields, rolling them down in the spring us-ing a 10-foot rolling stalk chopper. This rollingchopper kills the rye or vetch cover crop andcreates a nice no-till mulch into which he plantsa variety of vegetable and grain crops. Afterseveral years of no-till production, his soils aremellow and easy to plant into. Groff farms 175

acres of vegetables, alfalfa, and grain crops onhis Cedar Meadow Farm. Learn more abouthis operation in the Farmer Profiles section ofthis publication, by visiting his Web site, or byordering his video (see Additional Resourcessection).

Other conservation tillage systems include ridgetillage, minimum tillage, zone tillage, and re-duced tillage, each possessing some of the ad-vantages of both conventional till and no-till.These systems represent intermediate tillage sys-tems, allowing more flexibility than either a no-till or conventional till system might. They aremore beneficial to soil organisms than a con-ventional clean-tillage system of moldboardplowing and disking.

Adding manure and compost is a recognizedmeans for improving soil organic matter andhumus levels. In their absence, perennial grassis the only crop that can regenerate and increasesoil humus (18). Cool-season grasses build soilorganic matter faster than warm-season grassesbecause they are growing much longer duringa given year (18). When the soil is warmenough for soil organisms to decompose organicmatter, cool-season grass is growing. Whilegrowing, it is producing organic matter andcycling minerals from the decomposing organicmatter in the soil. In other words, there is a netgain of organic matter because the cool-seasongrass is producing organic matter faster than itis being used up. With warm-season grasses,organic matter production during the growingseason can be slowed during the long dormantseason from fall through early spring. Duringthe beginning and end of this dormant period,the soil is still biologically active, yet no grassgrowth is proceeding (18). Some net accumu-lation of organic matter can occur under warm-season grasses, however. In a Texas study,switchgrass (a warm-season grass) grown forfour years increased soil carbon content from1.1% to 1.5% in the top 12 inches of soil (19). Inhot and moist regions, a cropping rotation thatincludes several years of pasture will be mostbeneficial.

Effect of Nitrogen on Organic Matter

Excessive nitrogen applications stimulate in-creased microbial activity, which in turn speedsorganic matter decomposition. The extra nitro-

From Boyle et al., 1989 (13).

Table 6. Tillage effects on water infiltration andground cover.

Water Infiltration Ground Cover mm/minute Percent

No-till 2.7 48Chisel Plow 1.3 27Moldboard Plow 0.8 12


gen narrows the ratio of carbon to nitrogen inthe soil. Native or uncultivated soils have ap-proximately 12 parts of carbon to each part ofnitrogen, or a C:N ratio of 12:1. At this ratio,populations of decay bacteria are kept at a stablelevel (20), since additional growth in their popu-lation is limited by a lack of nitrogen. Whenlarge amounts of inorganic nitrogen are added,the C:N ratio is reduced, which allows the popu-lations of decay organisms to explode as theydecompose more organic matter with the nowabundant nitrogen. While soil bacteria can ef-ficiently use moderate applications of inorganicnitrogen accompanied by organic amendments(carbon), excess nitrogen results in decomposi-tion of existing organic matter at a rapid rate.Eventually, soil carbon content may be reducedto a level where the bacterial populations areon a starvation diet. With little carbon avail-able, bacterial populations shrink, and less ofthe free soil nitrogen is absorbed. Thereafter,applied nitrogen, rather than being cycledthrough microbial organisms and re-released toplants slowly over time, becomes subject toleaching. This can greatly reduce the efficiencyof fertilization and lead to environmental prob-lems.

To minimize the fast decomposition of soil or-ganic matter, carbon should be added with ni-trogen. Typical carbon sources�such as greenmanures, animal manure, and compost�servethis purpose well.

Amendments containing too high a carbon tonitrogen ratio (25:1 or more) can tip the balancethe other way, resulting in nitrogen being tiedup in an unavailable form. Soil organisms con-sume all the nitrogen in an effort to decomposethe abundant carbon; tied up in the soil organ-isms, nitrogen remains unavailable for plantuptake. As soon as a soil microorganism diesand decomposes, its nitrogen is consumed byanother soil organism, until the balance be-tween carbon and nitrogen is achieved again.

Fertilizer Amendments andFertilizer Amendments andFertilizer Amendments andFertilizer Amendments andFertilizer Amendments andBiologically Active SoilsBiologically Active SoilsBiologically Active SoilsBiologically Active SoilsBiologically Active Soils

What are the soil mineral conditions that fosterbiologically active soils? Drawing from thework of Dr. William Albrecht (1888 to 1974),agronomist at the University of Missouri, welearn that balance is the key. Albrecht advocatedbringing soil nutrients into a balance so that nonewere in excess or deficient. Albrecht�s theory(also called base-saturation theory) is used toguide lime and fertilizer application by measur-ing and evaluating the ratios of positivelycharged nutrients (bases) held in the soil. Posi-tively charged bases include calcium, magne-sium, potassium, sodium, ammonium nitrogen,and several trace minerals. When optimum ra-tios of bases exist, the soil is believed to supporthigh biological activity, have optimal physicalproperties (water intake and aggregation), andbecome resistant to leaching. Plants growingon such a soil are also balanced in mineral lev-els and are considered to be nutritious to hu-mans and animals alike. Base saturation per-centages that Albrecht�s research showed to beoptimal for the growth of most crops are:

Calcium 60�70%Magnesium 10�20%Potassium 2�5%Sodium 0.5�3%Other bases 5%

According to Albrecht, fertilizer and lime ap-plications should be made at rates that will bringsoil mineral percentages into this ideal range.This approach will shift the soil pH automati-cally into a desirable range without creatingnutrient imbalances. The base saturation theoryalso takes into account the effect one nutrientmay have on another and avoids undesirableinteractions. For example, phosphorus is knownto tie up zinc.

The Albrecht system of soil evaluation contrastswith the approach used by many state labora-tories, often called the �sufficiency method.�Sufficiency theory places little to no value onnutrient ratios, and lime recommendations aretypically based on pH measurements alone.While in many circumstances base saturationand sufficiency methods will produce identical

Excessive nitrogen stimulatesincreased microbial activity,which in turn speeds organicmatter decomposition.


soil recommendations and similar results, sig-nificant differences can occur on a number ofsoils. For example, suppose we tested a corn-field and found a soil pH of 5.5 and base satu-ration for magnesium at 20% and calcium at40%. Base saturation theory would call for lim-ing with a high-calcium lime to raise the per-cent base saturation of calcium; the pH wouldrise accordingly. Sufficiency theory would notspecify high-calcium lime and the grower mightchoose instead a high-magnesium dolomite limethat would raise the pH but worsen the balanceof nutrients in the soil. Another way to look atthese two theories is that the base saturationtheory does not concern itself with pH to anygreat extent, but rather with the proportionalamounts of bases. The pH will be correct whenthe levels of bases are correct.

Albrecht�s ideas have found their way ontolarge numbers of American farms and into theprograms of several agricultural consulting com-panies. Neal Kinsey, a soil fertility consultantin Charleston, Missouri, is a major proponentof the Albrecht approach. Kinsey was a stu-dent under Albrecht and is one of the leadingauthorities on the base-saturation method. Heteaches a short course on the Albrecht systemand provides a soil analysis service (21). Hisbook, Hands On Agronomy, is widely recognizedas a highly practical guide to the Albrecht sys-tem. ATTRA can provide more information onAlbrecht Fertility Management Systems.

Several firms�many providing backup fertilizerand amendment products�offer a biological-farming program based on the Albrecht theory.Typically these firms offer broad-based soilanalysis and recommend balanced fertilizermaterials considered friendly to soil organisms.They avoid the use of some common fertilizersand amendments such as dolomite lime, potas-sium chloride, anhydrous ammonia, and oxideforms of trace elements because they are con-sidered harmful to soil life. The publication Howto Get Started in Biological Farming presents sucha program. See the Additional Resources sec-tion for ordering information. For names of com-panies offering consulting and products, orderthe ATTRA publications Alternative Soil Testing

Laboratories and Sources of Organic Fertilizers andAmendments. Both of these are also availableon the ATTRA Web site located at <http://www.attra.ncat.org>.

Conventional FertilizersConventional FertilizersConventional FertilizersConventional FertilizersConventional Fertilizers

Commercial fertilizer can be a valuable resourceto farmers in transition to a more sustainablesystem and can help meet nutrient needs dur-ing times of high crop nutrient demand or whenweather conditions result in slow nutrient re-lease from organic resources. Commercial fer-tilizers have the advantage of supplying plantswith immediately available forms of nutrients.They are often less expensive and less bulky toapply than many natural fertilizers.

Not all conventional fertilizers are alike. Manyappear harmless to soil livestock, but some arenot. Anhydrous ammonia contains approxi-mately 82% nitrogen and is applied subsurfaceas a gas. Anhydrous speeds the decompositionof organic matter in the soil, leaving the soilmore compact as a result. The addition of an-hydrous causes increased acidity in the soil, re-quiring 148 pounds of lime to neutralize 100pounds of anhydrous ammonia, or 1.8 poundsof lime for every pound of nitrogen containedin the anhydrous (22). Anhydrous ammoniainitially kills many soil microorganisms in theapplication zone. Bacteria and actinomycetesrecover within one to two weeks to levels higherthan those prior to treatment (23). Soil fungi,however, may take seven weeks to recover.During the recovery time, bacteria are stimu-lated to grow more, and decompose more or-ganic matter, by the high soil nitrogen content.As a result, their numbers increase after anhy-drous applications, then decline as available soilorganic matter is depleted. Farmers commonlyreport that the long-term use of synthetic fertil-izers, especially anhydrous ammonia, leads tosoil compaction and poor tilth (23). When bac-terial populations and soil organic matter de-crease, aggregation declines, because existingglues that stick soil particles together are de-graded, and no other glues are being produced.

http://attra.ncat.org/attra-pub/soil-lab.html



http://attra.ncat.org/attra-pub/orgfert.html

http://attra.ncat.org/attra-pub/orgfert.html

http://www.attra.ncat.org

http://www.attra.ncat.org


Potassium chloride (KCl) (0-0-60 and 0-0-50),also known as muriate of potash, contains ap-proximately 50 to 60% potassium and 47.5%chloride (24). Muriate of potash is made by re-fining potassium chloride ore, which is a mix-ture of potassium and sodium salts and clayfrom the brines of dying lakes and seas. Thepotential harmful effects from KCl can be sur-mised from the salt concentration of the mate-rial. Table 7 shows that, pound for pound, KClis surpassed only by table salt onthe salt index. Additionally, someplants such as tobacco, potatoes,peaches, and some legumes areespecially sensitive to chloride.High rates of KCl must be avoidedon such crops. Potassium sulfate, potassium ni-trate, sul-po-mag, or organic sources of potas-sium may be considered as alternatives to KClfor fertilization.

Sodium nitrate, also known as Chilean nitrateor nitrate of soda, is another high-salt fertilizer.Because of the relatively low nitrogen contentof sodium nitrate, a high amount of sodium isadded to the soil when normal applications ofnitrogen are made with this material. The con-cern is that excessive sodium acts as a dispers-ant of soil particles, degrading aggregation. Thesalt index for KCl and sodium nitrate can beseen in Table 7.

TTTTTop$oil – Yop$oil – Yop$oil – Yop$oil – Yop$oil – YourourourourourFarm’$ CapitalFarm’$ CapitalFarm’$ CapitalFarm’$ CapitalFarm’$ Capital

Topsoil is the capital reserve of every farm. Eversince mankind started agriculture, erosion oftopsoil has been the single largest threat to a

Table 7. Salt index for various fertilizers.

Sodium chloride 153 2.9

Potassium chloride 116 1.9

Ammonium nitrate 105 3.0

Sodium nitrate 100 6.1

Urea 75 1.6

Potassium nitrate 74 1.6

Ammonium sulfate 69 3.3

Calcium nitrate 53 4.4

Anhydrous ammonia 47 .06

Sulfate-potash-magnesia 43 2.0

Di-ammonium phosphate 34 1.6

Monammonium phosphate 30 2.5

Gypsum 8 .03

Calcium carbonate 5 .01

Material Salt Index Salt index per unitof plant food

Protecting soil from erosion isthe first step toward a sustain-able agriculture.


soil�s productivity�and, consequently, to farmprofitability. This is still true today. In the U.S.,the average acre of cropland is eroding at a rateof 7 tons per year (2). To sustain agriculturemeans to sustain soil resources, because that�sthe source of a farmer�s livelihood.

The major productivity costs to the farm associ-ated with soil erosion come from the replace-ment of lost nutrients and reduced water hold-ing ability, accounting for 50 to 75% of produc-tivity loss (2). Soil that is removed by erosiontypically contains about three times more nu-trients than the soil left behind and is 1.5 to 5times richer in organic matter (2). This organicmatter loss not only results in reduced waterholding capacity and degraded soil aggregation,but also loss of plant nutrients, which must thenbe replaced with nutrient amendments.

Five tons of topsoil (the so-called tolerance level)can easily contain 100 pounds of nitrogen, 60pounds of phosphate, 45 pounds of potash, 2pounds of calcium, 10 pounds of magnesium,and 8 pounds of sulfur. Table 8 shows the ef-fect of slight, moderate, and severe erosion onorganic matter, soil phosphorus level, and plant-available water on a silt loam soil in Indiana(25).

When erosion by water and wind occurs at arate of 7.6 tons/acre/year it costs $40 per acreeach year to replace the lost nutrients as fertil-izer and around $17/acre/year to pump wellirrigation water to replace the soil water hold-ing capacity of that lost soil (26). The total costof soil and water lost annually from U.S. crop-land amounts to an on-site productivity loss ofapproximately $27 billion each year (2).

Water erosion gets started when falling rainwa-ter collides with bare ground and detaches soilparticles from the parent soil body. Afterenough water builds up on the soil surface, fol-lowing detachment, overland water flow trans-ports suspended soil down-slope (Figure 5).Suspended soil in the runoff water abrades anddetaches additional soil particles as the watertravels overland. Preventing detachment is themost effective point of erosion control becauseit keeps the soil in place. Other erosion controlpractices seek to slow soil particle transport andcause soil to be deposited before it reachesstreams. These methods are less effective at pro-tecting the quality of soil within the field.

Commonly implemented practices to slow soiltransport include terraces and diversions. Ter-races, diversions, and many other erosion �con-trol� practices are largely unnecessary if theground stays covered year-round. For erosionprevention, a high percentage of ground coveris a good indicator of success, while bare groundis an �early warning� indicator for a high riskof erosion (27). Muddy runoff water and gul-lies are �too-late� indicators. The soil has al-ready eroded by the time it shows up as muddywater, and it�s too late to save soil already sus-pended in the water.

Protecting the soil from erosion is the first steptoward a sustainable agriculture. Since watererosion is initiated by raindrop impact on baresoil, any management practice that protects thesoil from raindrop impact will decrease erosionand increase water entry into the soil. Mulches,cover crops, and crop residues serve this pur-pose well.

From Schertz et al., 1984. (24)

Table 8. Effect of erosion on organic matter phosphorus and plant-available water.

Organic matter Phosphorus Plant-available waterErosion levelLbs./ac

Slight

Moderate

Severe

3.0

2.5

1.9

62

61

40

7.4

6.2

3.6

%%


Additionally, well-aggregated soils resist crust-ing because water-stable aggregates are lesslikely to break apart when the raindrop hitsthem. Adequate organic matter with high soilbiological activity leads to high soil aggregation.

Many studies have shown that cropping sys-tems that maintain a soil-protecting plantcanopy or residue cover have the least soil ero-sion. This is universally true. Long-term crop-ping studies begun in 1888 at the University ofMissouri provide dramatic evidence of this.Gantzer and colleagues (28) examined the ef-fects of a century of cropping on soil erosion.They compared depth of topsoil remaining af-ter 100 years of cropping (Table 9). As the tableshows, the cropping system that maintained thehighest amount of permanent ground cover(timothy grass) had the greatest amount of top-soil left.

The researchers commented that subsoil hadbeen mixed with topsoil in the continuous cornplots from plowing, making the real topsoildepth less than was apparent. In reality, all thetopsoil was lost from the continuous corn plotsin only 100 years. The rotation lost about halfthe topsoil over 100 years. How can we feedfuture generations with this type of farmingpractice?

In a study of many different soil types in eachof the major climatic zones of the U.S., research-ers showed dramatic differences in soil erosionwhen comparing row crops to perennial sods.Row crops consisted of cotton or corn, and sodcrops were bluegrass or bermuda grass. Onaverage, the row crops eroded more than 50times more soil than did the perennial sod crops.The two primary influencing factors are groundcover and tillage. The results are shown in Table10.

So, how long do fields have before the topsoil isgone? This depends on where in the countrythe field is located. Some soils naturally havevery thick topsoil, while other soils have thintopsoil over rock or gravel. Roughly 8 tons/acre/year of soil-erosion loss amounts to thethickness of a dime spread over an acre. Twentydimes stack up to 1-inch high. So a landscapewith an 8-ton erosion rate would lose an inchof topsoil about every 20 years. On a soil with athick topsoil, this amount is barely detectablewithin a person�s lifetime and may not be no-

Figure 5. Raindrops falling on bare ground initiate erosion.Drawing from cropland monitoring guide (27).

*Corn, oats, wheat, clover, timothyFrom: Gantzer et al. (28).

Table 9. Topsoil depth remaining after 100years of different cropping practices.

Inches of topsoilremaining

Continuous Corn6-year rotation*Continuous timothy grass

7.7 12.2

17.4

Crop Sequence


ticed. Soils with naturally thin topsoils or top-soils that have been previously eroded can betransformed from productive to degraded landwithin a generation.

Forward-thinking researcher Wes Jackson, ofthe Land Institute, waxes eloquent about howtillage has become engrained in human culturesince we first began farming. Beating ourswords into plowshares surely embodies the tri-umph of good over evil. Someone who createssomething new is said to have �plowed newground.� �Yet the plowshare may well havedestroyed more options for future generationsthan the sword� (30).

Tillage for the production of annual crops is themajor problem in agriculture, causing soil ero-sion and the loss of soil quality. Any agricul-tural practice that creates and maintains bareground is inherently less sustainable than prac-tices that keep the ground covered throughoutthe year. Wes Jackson has spent much of hiscareer developing perennial grain crops andcropping systems that mimic the natural prai-rie. Perennial grain crops do not require tillageto establish year after year, and the ground isleft covered. Ultimately, this is the future of grainproduction and truly represents a new visionfor how we produce food. The greatest researchneed in agriculture today is breeding work todevelop perennial crops that will replace annualcrops requiring tillage. Farming practices us-ing annual crops in ways that mimic perennial

systems, such as no-till and cover crops, are ourbest alternative until perennial systems are de-veloped.

SummarSummarSummarSummarSummary of Part Iy of Part Iy of Part Iy of Part Iy of Part I

Soil management involves stewardship of thesoil livestock herd. The primary factors affect-ing organic matter content, build-up, and de-composition rate in soils are oxygen content, ni-trogen content, moisture content, temperature,and the addition and removal of organic mate-rials. All these factors work together all the time.Any one can limit the others. These are the fac-tors that affect the health and reproductive rateof organic matter decomposer organisms. Man-agers need to be aware of these factors whenmaking decisions about their soils. Let�s takethem one at a time.

Increasing oxygen speeds decomposition of or-ganic matter. Tillage is the primary way extraoxygen enters the soil. Texture also plays a role,with sandy soils having more aeration thanheavy clay soils. Nitrogen content is influencedby fertilizer additions. Excess nitrogen, with-out the addition of carbon, speeds the decom-position of organic matter. Moisture content af-fects decomposition rates. Soil microbial popu-lations are most active over cycles of wettingand drying. Their populations increase follow-ing wetting, as the soil dries out. After the soilbecomes dry, their activity diminishes. Just like

Table 10. Effect of cropping on soil erosion rates

Soil type Location Slope Row crop soil loss Sod soil loss

Silt loamLoamSilt loamFine sandyloamClay loamFine sandyloamClaySilt loamAverage

IowaMissouriOhioOklahoma

N. CarolinaTexas

TexasWisconsinAverage

State %

98

127.7

108.7

4169.4

Tons/ac

38519919

3124

2111149

Tons/ac

.02

.16

.02

.02

.31

.08

.02

.10

.09

Adapted from Shiflet and Darby, 1985 (29).


humans, soil organisms are profoundly affectedby temperature. Their activity is highest withina band of optimum temperature, above andbelow which their activity is diminished.

Adding organic matter provides more food formicrobes. To achieve an increase of soil organicmatter, additions must be higher than remov-als. Over a given year, under average condi-tions, 60 to 70 percent of the carbon containedin organic residues added to soil is lost as car-bon dioxide (20). Five to ten percent is assimi-lated into the organisms that decomposed theorganic residues, and the rest becomes �new�humus. It takes decades for new humus to de-velop into stable humus, which imparts thenutrient-holding characteristics humus isknown for (20). The end result of adding a tonof residue would be 400 to 700 pounds of newhumus. One percent organic matter weighs20,000 pounds per acre. A 7-inch depth of top-soil over an acre weighs 2 million pounds.Building organic matter is a slow process.

It is more feasible to stabilize and maintain thehumus present, before it is lost, than to try torebuild it. The value of humus is not fully real-ized until it is severely depleted (20). If yoursoils are high in humus now, work hard to pre-serve what you have. The formation of newhumus is essential to maintaining old humus,and the decomposition of raw organic matterhas many benefits of its own. Increased aera-tion caused by tillage coupled with the absenceof organic carbon in fertilizer materials hascaused more than a 50% decline in native hu-mus levels on many U.S. farms (20).

Appropriate mineral nutrition needs to bepresent for soil organisms and plants to pros-per. Adequate levels of calcium, magnesium,potassium, phosphorus, sodium, and the traceelements should be present, but not in excess.The base saturation theory of soil managementhelps guide decision-making toward achievingoptimum levels of these nutrients in the soil.Several books have been written on balancingsoil mineral levels, and several consulting firmsprovide soil analysis and fertility recommenda-tion services based on this theory.

Commercial fertilizers have their place in sus-tainable agriculture. Some appear harmless tosoil livestock and provide nutrients at times ofhigh nutrient demand from crops. Anhydrousammonia and potassium chloride cause prob-lems, however. As noted above, anhydrous killssoil organisms in the injection zone. Bacteriaand actinomycetes recover within a few weeks,but fungi take longer. The increase in bacteria,fed by highly available nitrogen from the anhy-drous, speeds the decomposition of organicmatter. Potassium chloride has a high salt in-dex, and some plants and soil organisms aresensitive to chloride.

Topsoil is the farmer�s capital. Sustaining agri-culture means sustaining the soil. Maintainingground cover in the form of cover crops, mulch,or crop residue for as much of the annual sea-son as possible achieves the goal of sustainingthe soil resource. Any time the soil is tilled andleft bare it is susceptible to erosion. Even smallamounts of soil erosion are harmful over time.It is not easy to see the effects of erosion over ahuman lifetime; therefore, erosion may go un-noticed. Tillage for production of annual cropshas created most of the erosion associated withagriculture. Perennial grain crops not requir-ing tillage provide a promising alternative fordrastically improving the sustainability of futuregrain production.

SummarSummarSummarSummarSummary of Sustainable Soily of Sustainable Soily of Sustainable Soily of Sustainable Soily of Sustainable SoilManagement PrinciplesManagement PrinciplesManagement PrinciplesManagement PrinciplesManagement Principles

� Soil livestock cycle nutrients andprovide many other benefits.

� Organic matter is the food for the soil live-stock herd.

� The soil should be covered to protect it fromerosion and temperature extremes.

� Tillage speeds the decomposition of organicmatter.

� Excess nitrogen speeds the decomposition oforganic matter; insufficient nitrogen slowsdown organic matter decomposition andstarves plants.


� Moldboard plowing speeds the decomposi-tion of organic matter, destroys earthwormhabitat, and increases erosion.

� To build soil organic matter, the produc-tion or addition of organic matter must ex-ceed the decomposition of organic matter.

� Soil fertility levels need to be within accept-able ranges before a soil-building programis begun.

1. Assess Soil Health and BiologicalActivity on Your Farm

A basic soil audit is the first and sometimes theonly monitoring tool used to assess changes inthe soil. Unfortunately, the standard soil testdone to determine nutrient levels (P, K, Ca, Mg,etc.) provides no information on soil biology andphysical properties. Yet most of the farmer-rec-ognized criteria for healthy soils (see p. 2) in-clude, or are created by, soil organisms and soilphysical properties. A better appreciation ofthese biological and physical soil properties, andhow they affect soil management and produc-tivity, has resulted in the adoption of severalnew soil health assessment techniques, whichare discussed below.

The USDA Soil Quality Test Kit

The USDA Soil Quality Institute provides a SoilQuality Test Kit Guide developed by Dr. JohnDoran and associates at the Agricultural Re-search Service�s office in Lincoln, Nebraska.Designed for field use, the kit allows the mea-surement of water infiltration, water holdingcapacity, bulk density, pH, soil nitrate, salt con-centration, aggregate stability, earthworm num-bers, and soil respiration. Components neces-sary to build a kit include many items commonlyavailable�such as pop bottles, flat-bladedknives, a garden trowel, and plastic wrap. Alsonecessary to do the tests is some equipment that

is not as readily available, such as hypodermicneedles, latex tubing, a soil thermometer, anelectrical conductivity meter, filter paper, andan EC calibration standard. The Soil QualityTest Kit Guide can be ordered from the USDAthrough the Soil Quality Institute�s Web page,< h t t p : / / s o i l s . u s d a . g o v / s q i / f i l e s /KitGuideComplete.pdf>. The 88-page on-lineversion of the guide is available in Adobe Acro-bat Reader format through the above Web pageand may be printed out. A summary of the testsis also available from the Web page. To order aprint version, see the Soil Quality Institute ref-erence under Additional Resources.

A greatly simplified and quick soil quality as-sessment is available at the Soil Quality Institute�sWeb page as well, by clicking on �Getting toKnow your Soil,� near the bottom of thehomepage. This simplified method involves dig-ging a hole and making some observations.Here are a few of the procedures shown at thisWeb site: Dig a hole 4 to 6 inches below the lasttillage depth and observe how hard the diggingis. Inspect plant roots to see whether there is alot of branching and fine root hairs or whetherthe roots are balled-up. A lack of fine root hairsindicates oxygen deprivation, while sidewaysgrowth indicates a hardpan. The process goeson to assess earthworms, soil smell, and aggre-gation. Another useful, hands-on procedure forassessing pasture soils is discussed in the ATTRApublication Assessing the Pasture Soil Resource.

Photo by USDA NRCS

PART II. MANAGEMENT STEPS TO IMPROVE SOIL QUALITY

http://soils.usda.gov/sqi/files/KitGuideComplete.pdf

http://soils.usda.gov/sqi/files/KitGuideComplete.pdf

http://attra.ncat.org/attra-pub/PDF/assess.pdf


Early Warning Monitoring for Croplands

A cropland monitoring guide has been pub-lished by the Center for Holistic Management(27). The guide contains a set of soil health in-dicators that are measurable in the field. Nofancy equipment is needed to make the assess-ments described in this monitoring guide. Infact, all the equipment is cheap and locally avail-able for almost any farm. Simple measurementscan help determine the health of croplands interms of the effectiveness of the nutrient cycleand water cycle, and the diversity of some soilorganisms. Assessments of living organisms,aggregation, water infiltration, ground cover,and earthworms can be made using this guide.The monitoring guide is easy to read and un-derstand and comes with a field sheet to recordobservations. It is available for $12 from theSavory Center for Holistic Management (seeAdditional Resources).

Direct Assessment of Soil Health

Some quick ways to identify a healthy soil in-clude feeling it and smelling it. Grab a handfuland take a whiff. Does it have an earthy smell?Is it a loose, crumbly soil with some earthwormspresent? Dr. Ray Weil, soil scientist at the Uni-versity of Maryland, describes how he wouldmake a quick evaluation of a soil�s health in justfive minutes (31).

Look at the surface and see if it is crusted, whichtells something about tillage practices used, or-ganic matter, and structure. Push a soil probe-down to 12 inches, lift out some soil and feel itstexture. If a plow pan were present it would havebeen felt with the probe. Turn over a shovelful ofsoil to look for earthworms and smell for actino-mycetes, which are microorganisms that help com-post and stabilize decaying organic matter. Theiractivity leaves a fresh earthy smell in the soil.

Two other easy observations are to count thenumber of soil organisms in a square foot ofsurface crop residue and to pour a pint of wa-ter on the soil and record the time it takes tosink in. Comparisons can be made using thesesimple observations, along with Ray Weil�sevaluation above, to determine how farm prac-tices affect soil quality. Some of the soil qualityassessment systems discussed above use these

and other observations and provide record keep-ing sheets to record your observations.

A Simple Erosion Demonstration

This simple procedure demonstrates the valueof ground cover. Tape a white piece of papernear the end of a three-foot-long stick. Holdthe stick in one hand so as to have the paperend within one inch of a bare soil surface (seeFigure 6). Now pour a pint of water onto thebare soil within two to three inches of the whitepaper and observe the soil accumulation on thewhite paper. Tape another piece of white pa-per to the stick and repeat the operation, thistime over soil with 100% ground cover, andobserve the accumulation of soil on the paper.Compare the two pieces of paper. This simpletest shows how effective ground cover can beat preventing soil particles from detaching fromthe soil surface.

2. Use Tools and Techniques to Build Soil

Can a cover crop be worked into your rotation?How about a high-residue crop or perennial

Figure 6. Simple erosion test.Drawing from Cropland monitoring guide (27).


sod? Are there economical sources of organicmaterials or manure in your area? Are thereways to reduce tillage and nitrogen fertilizer?Where feasible, bulky organic amendments maybe added to supply both organic matter andplant nutrients. It is particularly useful to ac-count for nutrients when organic fertilizers andamendments are used. Start with a soil test anda nutrient analysis of the material you are ap-plying. Knowing the levels of nutrients neededby the crop guides the amount of amendmentsapplied and can lead to significant reductionsin fertilizer cost. The nutrient composition oforganic materials can vary, which is all the morereason to determine the amount you have withappropriate testing. In addition to containingthe major plant nutrients, organic fertilizers cansupply many essential micronutrients. Propercalibration of the spreading equipment is im-portant to ensure accurate application rates.

Animal Manure

Manure is an excellent soil amendment, provid-ing both organic matter and nutrients. Theamount of organic matter and nitrogen in ani-mal manure depends on the feed the animalsconsumed, type of bedding used (if any), andwhether the manure is applied as a solid or liq-uid. Typical rates for dairy manure would be10 to 30 tons per acre or 4,000 to 11,000 gallonsof liquid for corn. At these rates the crop wouldget between 50 and 150 pounds of available ni-trogen per acre. Additionally, lots of carbonwould be added to the soil, resulting in no lossof soil organic matter. Residues from cropsgrown with this manure application and left onthe soil would also contribute or-ganic matter.

However, a common problemwith using manure as a nutrientsource is that application rates areusually based on the nitrogenneeds of the crop. Because somemanures have about as much phosphorus asthey do nitrogen, this often leads to a buildupof soil phosphorus. A classic example is chickenlitter applied to crops that require high nitro-gen levels, such as pasture grasses and corn.Broiler litter, for example, contains approxi-mately 50 pounds of nitrogen and phosphorusand about 40 pounds of potassium per ton.

Since an established fescue pasture needs twiceas much nitrogen as it does phosphorus, a com-mon fertilizer application would be about 50pounds of nitrogen and 30 pounds of phospho-rus per acre. If a ton of poultry litter were ap-plied to supply the nitrogen needs of the fescue,an over-application of phosphorus would result,because the litter has about the same levels ofnitrogen and phosphorus. Several years of lit-ter application to meet nitrogen needs can buildup soil phosphorus to excessive levels. One easyanswer to this dilemma is to adjust the manurerate to meet the phosphorus needs of the cropand to supply the additional nitrogen with fer-tilizer or a legume cover crop. On some farmsthis may mean that more manure is being pro-duced than can be safely used on the farm. Inthis case, farmers may need to find a way toprocess and sell (or barter) this excess manureto get it off the farm.

Compost

Composting farm manure and other organicmaterials is an excellent way to stabilize theirnutrient content. Composted manure is alsoeasier to handle, less bulky, and better smellingthan raw manure. A significant portion of raw-manure nutrients are in unstable, soluble forms.Such unstable forms are more likely to run off ifsurface-applied, or to leach if tilled into the soil.Compost is not as good a source of readily avail-able plant nutrients as raw manure. But com-post releases its nutrients slowly, thereby mini-mizing losses. Quality compost contains morehumus than its raw components because pri-mary decomposition has occurred during the

composting process. How-ever, it does not contribute asmuch of the sticky gums andwaxes that aggregate soil par-ticles together as does rawmanure, because these sub-stances are also released dur-ing the primary decomposi-

tion phase. Unlike manure, compost can beused at almost any rate without burning plants.In fact, some greenhouse potting mixes contain20 to 30% compost. Compost (like manure)should be analyzed by a laboratory to determinethe nutrient value of a particular batch and toensure that it is being used effectively to pro-duce healthy crops and soil, and not excessivelyso that it contributes to water pollution.

A common problem with us-ing manure as a nutrientsource is that applicationrates are usually based on thenitrogen needs of the crop.


Composting also reduces the bulk of raw or-ganic materials�especially manures, which of-ten have a high moisture content. However,while less bulky and easier to handle, compostscan be expensive to buy. On-farm compostingcuts costs dramatically, compared with buyingcompost. For more comprehensive informationon composting at the farm or the municipallevel, see the ATTRA publication Farm-ScaleComposting Resource List.

Cover Crops and Green Manures

Many types of plants can be grown as covercrops. Some of the more common ones includerye, buckwheat, hairy vetch, crimson clover,subterranean clover, red clover, sweet clover,cowpeas, millet, and forage sorghums. Each ofthese plants has some advantages over the oth-ers and differs in its area of adaptability. Covercrops can maintain or increase soil organic mat-ter if they are allowed to grow long enough toproduce high herbage. All too often, people getin a hurry and take out a good cover crop just aweek or two before it has reached its full poten-tial. Hairy vetch or crimson clover can yield upto 2.5 tons per acre if allowed to go to 25% bloomstage. A mixture of rye and hairy vetch canproduce even more.

In addition to organic matter benefits, legumecover crops provide considerable nitrogen forcrops that follow them. Consequently, the ni-trogen rate can be reduced following a produc-tive legume cover crop taken out at the correcttime. For example, corn grown following twotons of hairy vetch should produce high yieldsof grain with only half of the normal nitrogenapplication.

When small grains such as rye are used as covercrops and allowed to reach the flowering stage,additional nitrogen may be required to help off-set the nitrogen tie-up caused by the high car-bon addition of the rye residue. The same wouldbe true of any high-carbon amendment, suchas sawdust or wheat straw. Cover crops alsosuppress weeds, help break pest cycles, andthrough their pollen and nectar provide foodsources for beneficial insects and honeybees.They can also cycle other soil nutrients, makingthem available to subsequent crops as the greenmanure decomposes. For more information on

cover crops, see ATTRA�s Overview of CoverCrops and Green Manures. This publication iscomprehensive and provides many referencesto other available information on growing covercrops.

Humates

Humates and humic acid derivatives are a di-verse family of products, generally obtainedfrom various forms of oxidized coal. Coal-de-rived humus is essentially the same as humusextracts from soil, but there has been a reluc-tance in some circles to accept it as a worth-while soil additive. In part, this stems from abelief that only humus derived from recentlydecayed organic matter is beneficial. It is alsotrue that the production and recycling of organicmatter in the soil cannot be replaced by coal-derived humus.

However, while sugars, gums, waxes and simi-lar materials derived from fresh organic-matterdecay play a vital role in both soil microbiologyand structure, they are not humus. Only a smallportion of the organic matter added to the soilwill ever be converted to humus. Most will re-turn to the atmosphere as carbon dioxide as itdecays.

Some studies have shown positive effects ofhumates, while other studies have shown nosuch effects. Generally, the consensus is thatthey work well in soils with low organic mat-ter. In small amounts they do not produce posi-tive results on soils already high in organic mat-ter; at high rates they may tie up soil nutrients.

There are many humate products on the mar-ket. They are not all the same. Humate prod-ucts should be evaluated in a small test plot forcost effectiveness before using them on a largescale. Salespeople sometimes make exaggeratedclaims for their products. ATTRA can providemore information on humates upon request.

Reduced Tillage

While tillage has become common to many pro-duction systems, its effects on the soil can becounter-productive. Tillage smoothes the soilsurface and destroys natural soil aggregationsand earthworm channels. Porosity and water

http://attra.ncat.org/attra-pub/PDF/farmcompost.pdf




http://attra.ncat.org/attra-pub/PDF/covercrop.pdf

http://attra.ncat.org/attra-pub/PDF/covercrop.pdf


infiltration decrease following most tillage op-erations. Plow pans may develop in many situ-ations, particularly if soils are plowed withheavy equipment or when the soil is wet. Tilledsoils have much higher erosion rates than soilsleft covered with crop residue.

Because of all the problems associated with con-ventional tillage operations, acreage under re-duced tillage systems is increasing in America.Any tillage system that leaves in excess of 30%surface residue is considered a �conservationtillage� system by USDA (32). Conservation till-age includes no-till, zero-till, ridge-till, zone-till,and some variations of chisel plowing anddisking. These conservation till strategies andtechniques allow for establishing crops into theprevious crop�s residues, which are purposelyleft on the soil surface. The principal benefits ofconservation tillage are reduced soil erosion andimproved water retention in the soil, resultingin more drought resistance. Additional benefitsthat many conservation tillage systems provideinclude reduced fuel consumption, flexibility inplanting and harvesting, reduced labor require-ments, and improved soil tilth. Two of the mostcommon conservation tillage systems are ridgetillage and no-till.

Ridge tillage is a form of conservation tillage thatuses specialized planters and cultivators tomaintain permanent ridges on which row cropsare grown. After harvest, crop residue is leftuntil planting time. To plant the next crop, theplanter places the seed in the top of the ridgeafter pushing residue out of the way and slic-ing off the surface of the ridge top. Ridges arere-formed during the last cultivation of the crop.

Often, a band of herbicide is applied to the ridgetop during planting. With banded herbicideapplications, two cultivations are generallyused: one to loosen the soil and another to cre-ate the ridge later in the season. No cultivationmay be necessary if the herbicide is applied bybroadcasting rather than banding. Becauseridge tillage relies on cultivation to control weedsand reform ridges, this system allows farmersto further reduce their dependence on herbi-cides, compared with either conventional till orstrict no-till systems.

Maintenance of the ridges is key to successfulridge tillage systems. The equipment must ac-curately reshape the ridge, clean away crop resi-due, plant in the ridge center, and leave a vi-able seedbed. Not only does the ridge-tillagecultivator remove weeds, it also builds up theridge. Harvesting in ridged fields may requiretall, narrow dual wheels fitted to the combine.This modification permits the combine tostraddle several rows, leaving the ridges undis-turbed. Similarly, grain trucks and wagons can-not be driven randomly through the field. Main-tenance of the ridge becomes a considerationfor each process.

Conventional no-till methods have been criti-cized for a heavy reliance on chemical herbi-cides for weed control. Additionally, no-tillfarming requires careful management and ex-pensive machinery for some applications. Inmany cases, the spring temperature of untilledsoil is lower than that of tilled soil. This lowertemperature can slow germination of early-planted corn or delay planting dates. Also, in-creased insect and rodent pest problems havebeen reported. On the positive side, no-till meth-ods offer excellent soil erosion prevention anddecreased trips across the field. On well-drainedsoils that warm adequately in the spring, no-tillhas provided the same or better yields than con-ventional till.

A recent equipment introduction into the no-till arena is the so-called �no-till cultivator.�These cultivators permit cultivation in heavyresidue and provide a non-chemical option topost-emergent herbicide applications. Farmershave the option to band herbicide in the rowand use the no-till cultivator to clean the middlesas a way to reduce herbicide use. ATTRA canprovide a number of resource contacts on cul-tural methods, equipment, and management forconservation-till cropping systems.

Minimize Synthetic Nitrogen Use

If at all possible, add carbon with nitrogensources. Animal manure is a good way to addboth carbon and nitrogen. Growing legumesas a green manure or rotation crop is anotherway. When using nitrogen fertilizer, try to do


it at a time when a heavy crop residue is goingonto the soil, too. For example, a rotation ofcorn, beans, and wheat would do well with ni-trogen added after the corn residue was rolleddown or lightly tilled in. Spring-planted soy-beans would require no nitrogen. A smallamount of nitrogen could be applied in the fallfor the wheat. Following the wheat crop, a le-gume winter-annual cover crop could beplanted. In the spring, when the cover crop istaken out, nitrogen rates for the corn would bereduced to account for the nitrogen in the le-gume. Avoid continual hay crops accompaniedby high nitrogen fertilization. The continualremoval of hay accompanied by high nitrogenspeeds the decomposition of soil organic mat-ter. Heavy fertilization of silage crops, whereall the crop residue is removed (especially whenaccompanied by tillage), speeds soil decline andorganic matter depletion.

3. Continue to Monitor for Indicators ofSuccess or Failure

As you experiment with new practices andamendments, continue to monitor the soil forchanges using some of the tools discussed abovein Assess Soil Health and Biological Activity.Several of these monitoring guides have sheetsyou can use in the field to record data and usefor future comparison after changes are madeto the farming practices. Review the principlesof sustainable soil management and find waysto apply them in your operation. If the thoughtof pulling everything together seems over-whelming, start with only one or two new prac-tices and build on them. Seek additional moti-vation by reading the next section on peoplewho have successfully built their soils.

Steve GroffSteve and his family produce vegetables, alfalfa,and grain crops on 175 acres in LancasterCounty, Pennsylvania. When Steve took overoperation of the family farm 15 years ago, hisnumber one concern was eliminating soil ero-sion. Consequently, he began using cover cropsextensively in his fields. In order to transformhis green cover crop into no-till mulch, Steve

uses a 10-foot Buffalo rolling stalk chopper.Under the hitch-mounted frame, the stalk chop-per has two sets of rollers running in tandem.These rollers can be adjusted for light or aggres-sive action and set for continuous coverage.Steve says the machine can be run up to eightmiles an hour and does a good job of killing thecover crop and pushing it right down on thesoil. It can also be used to flatten down other

Photo by USDA NRCS

Photo by USDA NRCS

PART III. EXAMPLES OF SUCCESSFUL SOIL BUILDERS (FARMER PROFILES)


crop residues after harvest. Steve improved hischopper by adding independent linkages andsprings to each roller. This modification makeseach unit more flexible and allows continuoususe over uneven terrain. Other farmers reportsimilar results using a disk harrow with thegangs set to run straight or at a slight angle.Following his cover crop chopping, Steve trans-plants vegetable seedlings into the killed mulch;sweet corn and snap beans are direct-seeded.Since conversion to a cover crop mulch system,his soils are protected from erosion and havebecome much mellower. For more informationon his system, order Steve�s videos listed underAdditional Resources, or visit his Web page at<http://www.cedarmeadowfarm.com/about.html>.At Steve�s Web site you can see photos of hiscover crop roller and no-till transplanter in ac-tion, as well as test-plot results comparing flailmowing, rolling, and herbicide killing of covercrops.

Bob WillettBob started no-tilling 20 years ago on his cornand soybean farm in Pride, Kentucky. He notonly reduced his machinery costs by switchingto no-till but also made gains in conserving top-soil. His goal is to develop a healthy level ofhumus in the top two inches, which keeps theseed zone loose. He has stopped the sidewallcompaction in the seed slot that still plagues hisneighbors during wet springs. He attributes thisimprovement to the increase in humus and or-ganic matter. His soil surface layer is crumblyand doesn�t smear when the disk openers passthrough. Bob proclaims that earthworms takethe place of tillage by incorporating residue andconverting it to humus. Worms help aerate hissoil and improve internal drainage, which con-tributes to good rooting for his crops (33).

David IlesOn the Iles�s North Carolina dairy farm the soilhas actually changed from red to a dark, almostblack color since conversion to no-till in 1970.David first learned about no-till from his col-lege professor at North Carolina State Univer-sity in 1964. Before he switched to no-till,David�s corn silage yielded between 12 and 15tons per acre in years with adequate rainfall and4 to 5 tons in dry years�indicating that mois-

ture was his major limiting factor (34). Davidrealized that his water runoff losses and soilerosion were a direct result of tillage. Address-ing the root cause of the problem, he switchedto no-till and began to spread manure on 1/3of his land annually. Since these changes, soilwater is no longer limiting. With adequate rain-fall he makes nearly 20 tons of silage now. Davidsays his land is vastly more productive, withincreased cation exchange capacity and in-creased phosphorus levels due to the humuspresent in his soil. Though his soil pH ranges inthe 5.6 to 5.8 level, he applies no lime. His fieldsare more productive now than when he appliedlime in the �70s and more productive than thoseof his neighbors who currently use lime and fer-tilizer.

David laments that this country has lost half ofits topsoil in less than 100 years (34). NorthCarolina State agronomist Bobby Brock agreesand says that for the first time in history we havethe opportunity to produce food and build soilat the same time. David reasons that no-till isthe way to improve the soil structure, increasetilth, and increase productivity while still prac-ticing intensive agriculture. He realizes thatorganic matter is the engine that drives his sys-tem and provides food for earthworms and mi-croorganisms. David built his soil by fallowingout 20 to 25 acres of his 380-acre farm each year.On these fallow acres he spreads manure andthen sows crops that are not harvested butgrown just for their organic matter. Even weedsare not clipped but left for their organic matter.David loves his earthworms and says they arethe best employees he has. �They work all thetime and eat dirt for a living� (34).

His best field is one he cleared himself in the�70s. In spite of traditional native pHs in thehigh 4s in his area, he did not lime this newground but instead just planted rye on it. Hehad a fine rye crop that year, so he appliedmanure liberally and planted rye a second time.His second rye crop was excellent as well andwas followed by corn the third year. That fieldyielded the most corn on the entire farm. Thisfield has been in continuous corn since 1981 andhas never been fertilized with conventionalproducts or tilled (34). This field has a pH of

http://www.cedarmeadowfarm.com/about.html


6.1 at a 6-inch depth, an exchange capacity of8, and an 80% base saturation. David believesthis field�s productivity is high because it hasnever been harmed by tillage.

ReferencesReferencesReferencesReferencesReferences

1) Cramer, Craig. 1994. Test your soils�health�first in a series. The New Farm.January. p. 17�21.

2) Pimentel, D., et al. 1995. Environmentaland economic costs of soil erosion and con-servation benefits. Science. Vol. 267, No.24. p. 1117�1122.

3) U.S. Department of Agriculture. 1998.Soil Biodiversity. Soil Quality InformationSheet, Soil Quality Resource Concerns.January. 2 p.

4) Edwards, Clive A., and P.J. Bohlen. 1996.Biology and Ecology of Earthworms.Chapman and Hall, New York. 426 p.

5) Edwards, Clive A., and Ian Burrows.1988. The potential of earthworm com-posts as plant growth media. p. 211-219.In: Earthworms in Waste and Environmen-tal Management. C.A. Edwards and E.F.Neuhauser (eds.). SPB AcademicPublishing, The Hague, The Netherlands.

6) Graff, O. 1971. Stikstoff, phosphor und-kalium in der regenwormlosung auf der-wiesenversuchsflche des sollingprojektes.Annales de Zoologie: Ecologie Animale.Special Publication 4. p. 503�512.

7) Anon. 1997. Product choices help add toworm counts. Farm Industry News.February. p. 64

8) Kladivko, Eileen J. No date. Earthwormsand crop management. Agronomy Guide,AY-279. Purdue University Extension Ser-vice, West Lafayette, IN. 5 p.

9) Soil Foodweb. 1228 NE 2nd Street.Corvallis, OR.

10) Bollen, Walter B. 1959. Microorganismsand Soil Fertility. Oregon State College.Oregon State Monographs, Studies in Bac-teriology, No. 1. 22 p.

11) Jackson, William R. 1993. Organic SoilConditioning. Jackson Research Center,Evergreen, CO. 957 p.

12) Comis, Don. 1997. Glomalin�soil�ssuperglue. Agricultural Research. USDA�ARS. October. p. 22.

13) Boyle, M., W.T. Frankenberger, Jr.,and L.H. Stolzy. 1989. The influence oforganic matter on soil aggregation andwater infiltration. Journal of ProductionAgriculture. Vol. 2. p. 209�299.

14) Pipel, N. 1971. Crumb formation. En-deavor. Vol. 30. p. 77�81.

15) Land Stewardship Project. 1998. TheMonitoring Toolbox. White Bear Lake,MN. Page number unknown.

16) Allison, F.E. 1968. Soil aggregation�somefacts and fallacies as seen by a microbiolo-gist. Soil Science. Vol. 106, No. 2. p.136�143.

17) Reicosky, D.C., and M.J. Lindstrom. 1995.Impact of fall tillage on short-term carbondioxide flux. p. 177-187. In: R.Lal, J.Kimble, E. Levine, and B.A. Stewards(eds.). Soils and Global Change. LewisPublisher, Chelsea, MI.

18) Nation, Allan. 1999. Allan�s Observa-tions. Stockman Grass Farmer. January.p. 12-14.

19) Sanderson, M.A., et al. 1999. Switchgrasscultivars and germplasm for biomass feed-stock production in Texas. BioresourceTechnology. Vol. 67, No 3. p. 209�219.

20) Sachs, Paul D. 1999. Edaphos: Dynam-ics of a Natural Soil System, 2nd edition.The Edaphic Press. Newbury, VT. 197 p.


21) Kinsey�s Agricultural Services, 297 CountyHighway 357, Charleston, MO 63834573-683-3880

22) Tisdale, S.L., W.L. Nelson, and J.D. Beaton.1985. Soil Fertility and Fertilizers, 4thEdition. Macmillian Publishing Company,New York. 754 p.

23) Francis, Charles A., Cornelia B. Flora, andLarry D. King. 1990. Sustainable Agri-culture in Temperate Zones. John Wileyand Sons, Inc., New York. 487 p.

24) Parker, M.B., G.J. Gasho, and T.P. Gaines.1983. Chloride toxicity of soybeans grownon Atlantic coast flatwoods soils.Agronomy Journal. Vol. 75. p. 439�443.

25) Schertz. 1985. Field evaluation of the ef-fect of soil erosion on crop productivity.p. 9�17. In: Erosion and Soil Productivity.Proceedings of the National Symposiumon Erosion and Soil Productivity. Ameri-can Society of Agricultural Engineers. De-cember 10�11, 1984. New Orleans, LA.ASAE Publication 8-85.

26) Troeh, F.R., J.A Hobbs, and R.L. Donahue.1991. Soil and Water Conservation.Prentice Hall, Englewood Cliffs, NJ.

27) Sullivan, Preston G. 1998. Early Warn-ing Monitoring Guide for Croplands. Cen-ter for Holistic Management, Albuquerque,NM. 22 p.

28) Gantzer, C.J., S.H. Anderson, A.L. Thomp-son, and J.R. Brown. 1991. Evaluation ofsoil loss after 100 years of soil and cropmanagement. Agronomy Journal. Vol.83. p. 74�77.

29) Shiflet, T.N., and G.M. Darby. 1985. Table3.4: Effect of row and sod crops on runoffand erosion [from G.M. Browning, 1973].p. 26. In: M.E. Heath, R.F. Barnes, andD.S. Metcalfe (eds.). Forages: The Scienceof Grassland Agriculture, 4th ed. IowaState University Press, Ames, IA.

30) Jackson, Wes. 1980. New Roots for Agri-culture, 1st edition. Friends of the Earth,San Francisco, CA. 150 p.

31) Bowman, Greg. 1994. Why soil healthmatters. The New Farm. January. p. 10�16.

32) Magdoff, Fred. 1992. Building Soils forBetter Crops, 1st ed. University of Ne-braska Press, Lincoln, NE. 176 p.

33) Sickman, Tim. 1998. Building soil withresidue farming. Tennessee Farmer.August. p. 32, 34.

34) Dirnburger, J.M., and John M. Larose.1997. No-till saves dairy farm by healingthe harm that tillage has done. NationalConservation Tillage Digest. Summer.p. 5�8.

Additional ResourcesAdditional ResourcesAdditional ResourcesAdditional ResourcesAdditional Resources

Videos

No-till Vegetables. By Steve Groff. 1997.

This video leads you from selection of theproper cover crop mix to plant into, throughhow to control cover crops with little or noherbicide,as shown on Steve Groff�s Pennsyl-vania farm. You will see mechanical cover-crop-kill and vegetables being planted rightinto this mulch using a no-till transplanter.You�ll also hear comments from leading re-searchers in the no-till vegetable area. Orderthis video for $21.95 + $3.00 shipping from:

Cedar Meadow Farm679 Hilldale RoadHoltwood, PA 17532717-284-5152

Books and Periodicals

The Farmer�s Earthworm Handbook: Manag-ing Your Underground Money Makers. 1995.By David T. Ernst. Lessiter Publications,Brookfield, WI. 112 p.


To order, send $15.95 + $4.00 shipping andhandling to:

Lessiter Publications245 Regency CourtBrookfield, WI 53045262-782-4480800-645-8455

The Soul of Soil: A Guide to Ecological SoilManagement, 4th edition. 1995. By GraceGershuny and Joe Smillie. AgAccess, Davis, CA.158 p.


Fertile Ground Books3912 Vale Ave. Oakland, CA [email protected]://www.agribooks.com/

Neal Kinsey�s Hands-On Agronomy. 1993.By Neil Kinsey. Acres, USA. Metairie, LA.340 p.


ACRES USAP.O. Box 91299Austin, TX 78709-1299800-355-5313 (toll-free)512-892-4400

Building Soils for Better Crops, 2nd edition.2000. By Fred Magdoff and Harold van Es.University of Nebraska Press, Lincoln, NE.240 p.

To order, send $19.95 + $3.95 shipping to:

Sustainable Agriculture PublicationsHills Building, Room 10,University of VermontBurlington, VT 05405-0082802-656-0484;[email protected].

Edaphos: Dynamics of a Natural Soil System,2nd edition. 1999. By Paul D Sachs. TheEdaphic Press, Newbury, VT. 197 p.


North Country OrganicsP.O. Box 372Bradford, VT 05033802-222-4277

Soil Quality Test Kit. 1998. USDA. Soil Qual-ity Institute. 82 p.

This publication has detailed, step-by-stepinstructions with color photographs on howto assess soil quality, soil respiration, soilwater infiltration, bulk density, electricalconductivity, soil pH, soil nitrate, soil ag-gregate stability, slaking, and earthworms.It also covers soil physical observations andestimations and water quality tests, andincludes background information on the testsand appendices. To order this free test kitpublication, paid for by your federal tax dol-lars, contact:

Cathy A. SeyboldNRCS Soil Quality InstituteSoil Science DepartmentAgriculture and Life Sciences BuildingRoom 3017Oregon State UniversityCorvallis, OR [email protected]

or

Lee NorfleetNRCS Soil Quality InstituteNational Soil Dynamics Lab411 S. Donahue DriveAuburn, AL 36832334-844-4741, ext. [email protected]

Early Warning Monitoring for Croplands.1998. By Preston G. Sullivan. Center for Holis-tic Management, Albuquerque, NM. 22 p.

To order this guide, send $13.00 ppd. to:

Savory Center for Holistic Management1010 Tijeras, N.W.Albuquerque, NM 87102

mailto:[email protected]

http://www.agribooks.com/





505-842-5252http://www.holisticmanagement.org/

LaMotte Soil Handbook. 1994. Lamotte Com-pany. Chestertown, MD. 81 p.

Covers soil basics, nutrients, pH, acidityand alkalinity, and principles of the LaMottesoil testing system. Has relative nutrientand pH requirements for common crops andplants. To order this handbook ask for ref-erence # 1504 and send $4.85 to:

LaMotte CompanyP.O. Box 329Chestertown, MD 21620410-778-3100800-344-3100 (toll-free)410-778-6394 [email protected]://www.lamotte.com/

How to Get Started in Biological Farming. Nodate. Gary F. Zimmer. 11 p.

To order this publication, send $3 + $1 ship-ping to:

Midwestern Bio-AgHighway ID, Box 160Blue Mounds, WI 53517608-437-4994

Glomalin, a Manageable Soil Glue. 1999.Sara Wright. 1-page brochure.

To order this free publication contact:

Sara WrightUSDA-ARS-SMSLBldg. 001, Room 140, BARC-W10300 Baltimore AvenueBeltsville, MD 20705-2350301-504-8156http://www.ba.ars.usda.gov/sasl/research/glomalin/brochure.pdf

Soil Web Sites

Life in the Soilhttp://www.saburchill.com/chapters/chap0059.html

This excellent Web site includes briefoverviews of many subjects, includingnutrient transformation, biological degra-dation, soil structure, crop rotation,tillage, soil testing for microbes, andorganic matter turnover. Color photos ofmany soil critters with short descriptionsappear on the main Web page. Otherdrawings and black and white photos ofsoil microbes and their effects on soil areon other pages at this site.

The Pedosphere and its Dynamics: A SystemsApproach to Soil ScienceUniversity of Alberta�s Soil Sciencehttp://www.pedosphere.com/main.html

A complete on-line soils textbook coveringwhat soil is, ecological functions of soil, soiltexture, structure and color, soil formation,Canadian soil classification system, mineral-ogy, soil reaction, soil water, soil air, soil ecol-ogy, soil organic matter, and soil survey. Toview this textbook click on the textbook iconat the homepage. Much more information isavailable from the homepage, including edu-cational resources, tutorials, workshops, pub-lications, etc.

Soil Biological CommunitiesIdaho state office of the Bureau of Land Man-agementhttp://www.blm.gov/nstc/soil/

For drier areas, the Idaho state office of theBureau of Land Management has an interest-ing Web site on soil biological communitiesthat covers biological crusts, fungi, bacte-ria, protozoa, nematodes, arthropods, the soilfood web, and mammals. The site has manyphotographs that bring to life many of the soilinhabitants.

http://www.holisticmanagement.org/


http://www.lamotte.com/

http://www.ba.ars.usda.gov/sasl/research/glomalin/brochure.pdf

http://www.ba.ars.usda.gov/sasl/research/glomalin/brochure.pdf

http://www.saburchill.com/chapters/chap0059.html

http://www.saburchill.com/chapters/chap0059.html

http://www.pedosphere.com/main.html

www.id.blm.gov/iso/931/soil/

http://www.blm.gov/nstc/soil/


Soil Foodweb Inc.http://www.soilfoodweb.com/sfi_html/index.html

S. F .I. is the soil microbial analysis lab foundedby Dr. Elaine Ingham. In addition to generalbackground on the importance of the soilfoodweb, the Web site contains informationon commercial products and agriculturalpractices that support different microbialcommunities. This site has much interestinginformation, including how to have soil testedfor different soil organisms.

New Generation Cropping Systemsh t t p : / / w w w . c e d a r m e a d o w f a r m . c o m /about.html

This is the Web site describing Steve Groff�sinnovative Cedar Meadow Farm in LancasterCounty, Pennsylvania. Cedar Meadow is amodel sustainable agriculture farm. Steve andhis family grow corn, alfalfa, tomatoes, pump-kins, soybeans, small grains, and other veg-etables. They use no-till and mechanicallykilled cover crop mulches in a tight crop rota-tion. At this Web page you will see actionshots of no-till planting into mechanicallykilled cover crops and find ordering informa-tion for Steve Groff�s video mentioned above.

Soil Quality Information SheetsSoil Quality Institute, Natural Resources Con-servation Servicehttp://soils.usda.gov/sqi/soil_quality/what_is/sqiinfo.html

Produced by the Soil Quality Institute, Natu-ral Resources Conservation Service, this Website features on-line information sheets on soilquality topics. Among the topics are erosion,sedimentation, deposition, compaction, salinization, soil biodiversity, available water capacity, pesticides, indicators for soil qualityevaluation, organic matter, soil crusts, aggregate stability infiltration, and soil pH.

The electronic version of Sustainable SoilManagement is located at:HTMLhttp://www.attra.ncat.org/attra-pub/soilmgmt.htmlPDFhttp://www.attra.ncat.org/attra-pub/PDF/soilmgmt.pdf

By Preston SullivanNCAT Agriculture Specialist©2004 NCATMay 2004IP027Slot 133Version 062104

http://www.soilfoodweb.com/sfi_html/index.html

http://www.soilfoodweb.com/sfi_html/index.html



http://soils.usda.gov/sqi/soil_quality/what_is/sqiinfo.html

http://soils.usda.gov/sqi/soil_quality/what_is/sqiinfo.html

http://www.attra.ncat.org/attra-pub/soilmgmt.html

http://www.attra.ncat.org/attra-pub/PDF/soilmgmt.pdf

mailto:[email protected].?subject=Sustainable Soil Management