Oklahoma Homeowner’s Handbook for Soil

and Nutrient Management

Oklahoma Homeowner’s Handbook for Soil

and Nutrient Management

2nd Edition

Hailin Zhang and William R. RaunProfessors

Department of Plant and Soil SciencesOklahoma State University

E-1003

Foreword........................................................................................................................................... i

1 CompositionandGeneralSoilManagement............................................................................1

WhatMakesUpSoils?.................................................................................................................................................................... 1 PoorPhysicalConditionofSoil..................................................................................................................................................... 1 ImprovingSoilPhysicalCondition............................................................................................................................................... 2 LifeintheSoil................................................................................................................................................................................... 3 HereComestheGypsum................................................................................................................................................................ 3

2 AcidandBasicSoils:pH................................................................................................................5

WhatispH?...................................................................................................................................................................................... 5 NormalOccurrenceofAcidandAlkalineSoils........................................................................................................................... 5 ChangingSoilpH............................................................................................................................................................................. 6 BasicorAlkalineSoils..................................................................................................................................................................... 7

3 GrowthRequirementsforLandscapePlants.............................................................................9

PlantsandtheirEnvironment:PlantGrowthFactors................................................................................................................ 9 EssentialElementsforPlants......................................................................................................................................................... 9 Macronutrients................................................................................................................................................................................. 9 SecondaryNutrients.......................................................................................................................................................................11 Micronutrients.................................................................................................................................................................................11

4 GasandOilfortheGardenandLawn......................................................................................13

PlantNutrientUptakePatterns................................................................................................................................................... 13 KnowingWhenandHowMuchtoFertilize............................................................................................................................. 15

5 ManagingNitrogen.......................................................................................................................19

OrganicGardeningandNitrogen................................................................................................................................................ 19 TheNitrogenCycle........................................................................................................................................................................ 19 OrganicGardenersTakeNote...................................................................................................................................................... 20 InstantOrganicGardening........................................................................................................................................................... 21 SoilOrganicMatterMaintenance................................................................................................................................................ 21

6 NutrientSupplementsfortheSoil.............................................................................................23

NonsyntheticFertilizers................................................................................................................................................................ 23 SyntheticFertilizers....................................................................................................................................................................... 24 SingleandDoubleNutrientFertilizers....................................................................................................................................... 24 HandlingFertilizers....................................................................................................................................................................... 25

7 UsingSoilTestingtoGuideNutrientManagement...............................................................27

WhenandHowOftentoSoilTest............................................................................................................................................... 27

8 ReferenceTables............................................................................................................................33

Table of Contents

Oklahoma State University, in compliance with Title VI and VII of the Civil Rights Act of 1964, Executive Order 11246 as amended, Title IX of the Education Amendments of 1972, Americans with Disabilities Act of 1990, and other federal laws and regulations, does not discriminate on the basis of race, color, national origin, gender, age, religion, disability, or status as a veteran in any of its policies, practices, or procedures. This includes but is not limited to admissions, employment, financial aid, and educational services.

Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Robert E. Whitson, Director of Cooperative Extension Service, Oklahoma State University, Stillwater, Oklahoma. This publication is printed and issued by Oklahoma State University as authorized by the Vice President, Dean, and Director of the Division of Agricultural Sciences and Natural Resources and has been prepared and distributed at a cost of $7,624.59 for 4,000 copies. 0308 JA

Caringforhomelandscapesandgardeningcan,andshould,beanenjoyableand rewardingexperience.Theinformationinthishandbookisintendedtoimprovethechances of that happening. Many of the concepts andprinciples that are the foundation to interpreting anddiagnosing the needs and problems encountered in theyardandgarden,comefromdecadesofresearchanditsapplication in cultivated field crops.

Thebig,andexciting,differencebetweenmanagingsoilsforcultivatedcropproductionandtheurbanland-scape is scale. Farmers typically manage 80 acre fields (average size wheat field in Oklahoma) and enterprises thattotalabout500acres.Incontrast,theaverageurbanlandscape is about5,000 sq ft, or0.11acres. Intensivelymanaged areas, like a garden may be only 500 sq ft to1000sqft,or0.01to0.02acres.Selected,specialtyareasin the landscape, like a flower bed for azaleas, may occupy no more than 50 sq ft to 60 sq ft (3 ft x 20 ft), or only0.001acres.Managementdecisionsthatarefeasibleandappropriateforurbanlandscapesareneitherfeasiblenor appropriate for the average farmer. For example,we may decide that the best approach for long-term,successfulazaleagrowth is toremovea footofexistingclayeyalkalinesoilina50sqftareaandreplaceitwithasandy,acidicsoilmixture.Theprocesswillrequireapick-uploadofsoilremovedandapick-uploadofnewsoilmaterial to replace it. Replacing the top foot of a farm-er’s 80 acre field would require 70,000 pick-up loads of soil. Obviously this is not feasible.And so, while someofthefundamentalconceptsandprincipleslearnedfromcultivatedcropproductionresearchcanbeusefulwhen

transferredtomanagingthehomelandscape,thereverseisnotalwaystrue.Thus,organicgardeningcanbeeasilyimplemented,butorganicfarmingmaynotbecauseofashortage of organic material for large scale field input.

Small scale management of homeowner landscapesnot only makes some practices affordable, but also per-mitssomeunnecessarypracticesandmistakesthatwouldnotoccurinlargerscalesituations.These,especiallyinthecase of nutrient management will be identified as practices that can be eliminated or modified to save small inputs of moneyandeffort.Finally,therealvalueinacquiringnewknowledgefromreadingandstudyingthishandbookwillcomefromanimprovedabilitytomanageonacauseandeffectbasis.Thatis,beingabletorecognizeadysfunctioninthelandscapethatcanbetreatedandhowbesttotreatit.Forexample,yellowinginthelowerleavesofacornplantmaybecausedbyseveralconditions.Beingabletorecog-nize the symptoms of nitrogen deficiency should eliminate theriskoftreatingtheplantsfordiseaseorinsects.Under-standing the natural chemical and biological dynamicsof nitrogen in the soil will identify several options forcorrecting nitrogen deficiency in corn. Adding nitrogen fertilizerisonlyoneofthoseoptions.

Theauthorsgreatlyappreciatethecontributionfromthe two original authors: Dr. Gordon Johnson and Ms.Brenda Simons. Special thanks to Mr. Ray Ridlen andmanyotherExtensioneducatorsfor their inputsduringtherevisionofthishandbook.WearealsogratefultoMs.Vickie Brake for redrawing most of the figures, Dr. Hailin Zhangforthephotographs,andtoMs.JanelleMaloneforeditingandMs.JenniferAdsitforthegraphicdesignandproductionediting.

Foreword

i

ii

Chapter 1Composition and General Soil Management

What Makes Up Soils?

Inthemanagementofsoilsitisimportanttounder-standwhatmakesupsoilsandhowtheyareputtogether.AtypicalgardensoilismadeupofabouthalfsolidsandhalfvoidsasillustratedinFigure.1.1.

Poor Physical Condition of SoilOklahoma spring gardening conditions often lead

toadisruptionofthenormal,ideal,soilcondition.Avidgardeners,delayedby frequent rainyweather inMarchandApril,willdecidetoplantevenwhenthesoilisstillwetorworseyetwhenitisstillraining.Owningoneofthose fancy garden tillers that thoroughly mix the soilwhile theywalkalongsideguiding it, theywillattempttoprepareaseedbedwhenthesoilistoowet.Asaresult,soilparticlesarepackedclosetogether,forcingouttheairandwater.Foottracksoftenglistenfromwaterforcedtothesoilsurfacebecausetherearetoofewporestocontainthe water present. This soil condition, compared to thenormalsoilisillustratedinFigure1.3.

Compacting thesoilbycultivating itwhen it is toowet,redistributes thesoilcomponents,greatlyreducingtheamountofairandwaterthesoilcanhold.Whenthesoil finally dries, it still retains the compacted condition (often it will be as hard as a brick), and now holds much lessairandwater.Consequently,thegardenneedstobeirrigatedmorefrequentlytosupplyenoughwaterfortheplants,anditiseasytooverirrigateandnothaveenoughair for theroots tobreatheproperly.Theendresult isadisappointing garden. This condition will persist untilnaturalswellingandshrinkingofthesoilbroughtaboutby wetting and drying occurs, or the soil is cultivatedwhenitisinadry,crumblycondition.

Figure 1.1. General composition of soils.

Closer examination of soil solids, reveals they aremostlymineral,withonlyabout1%to2%organicmatterpresent.Themineralmattercanbefurthercategorizedbyparticlesizeintosand,silt,andclaymaterials.Thevoidsin soil are filled with either air or water, and in a well drainedsoil,adayorsoafter irrigationorrainfall,halfof the voids would be filled with air and half filled with water.Amorecompletedescriptionofthesoilcomposi-tionisillustratedinFigure1.2.

Themineralandorganiccomponentsprovideares-ervoirofnutrientsforplants,whichwillbediscussedingreaterdetail.Thevoids,orpores,holdingwaterareusu-allyanadequatesupplytomaintaintheneedsofplantsforseveraldays.Poresholdingairare justasimportanttoplantsasthoseholdingwaterbecauserootsrespire,aswedo, taking inoxygenandgivingoffcarbondioxide.Largesoilporesallowairexchangebetweenthesoilandtheatmosphere,assuringoxygenfortherootstofunctionnormally.

Voids50%

Solids50%

Figure 1.2. Distribution of air, water, mineral, and organic matter in a soil.

Air25%

Water25%

Mineral49% Organic

1%

j

1

Improving Physical Condition of Soil

Avoiding tillage when soils are wet will help pre-vent the soil from becoming compacted and hard. Inorder todo this, itmaybenecessary toavoid tillage inthespringaltogether.Eliminatingtillage,especiallyifonehasarelativelynew,expensivegardentiller,canbeadif-ficult change in management to implement. However, it is good to question the need for tillage and make surethere are good justifications for each operation (e.g. incor-porateexcessplantresidue,soilamendments,pesticides,etc.). Most of the time, tillage causes a deterioration of soil structure.

Gypsum

Itisacommonmythamonghomeownersthataddinggypsumtoclayeysoils,suchasarecommoninOklahoma,willimprovetheirphysicalcondition,makingthemsoftand easy to till. There is no scientific basis or research to support the claim that gypsum will soften hard, clayeysoils. One can only guess at how this practice came tobe.Perhapsanenthusiastichomeownerheardthatsomegypsum would be a good source of sulfur (it is) for plants. Itwouldhavebeeneasyfortheindividualtohavecheckedwitha farmsupplyoutlet forprices,andhaving founditavailableforafewdollarsaton,purchasedapick-upload of the off-white colored material for the garden.Afterspreadingit,thegardenerwouldhavefounditnec-essarytotillitmanytimestogetitthoroughlymixedandrestorethesoiltoitsoriginalcolor.Intheprocess,neigh-borsmayhavegatheredwonderingwhyitappearedtohavesnowedonthisgardenandnottheirs.Thegardenermayhaveexperiencedthebestgardencropinyearsand

attributethistothegypsum.Morelikelythegardenben-efited from the good deep tillage occasionally needed to break up hard pans or compacted layers of soil thatformatthenormaltillagedepth.Thehighrateofgypsumservedasagoodmarker,orindicatorofwhenthejobwasdone.Gypsumdoeshaveaplaceinthelandscapeasanamendmentforcorrectingsodicoralkalisoils,whichwillbefurtherexplained.

Raised Beds

Moundingsoilinrowsafootortwoabovedrainagewaysbetweenplantingsimprovesthedrainageofexcessrainfromthesoilandallowseasyaccesstoplantsgrowingonthemounds.Ifaninchofsandfollowedbyabouttwoinchesofstrawisplacedinthedrainagewaystheywillbeeasy towalk inandweedorharvestportionsof thegardenwhenitwouldotherwisebetoowet.Attheendoftheseasonthesandandstrawcanbeincorporatedintotheraisedbedtoimprovethatsoil,andnewlayersofsandandstrawplacedinthedrainagewaythefollowingyear.Raisedbedsmakeiteasiertomanagepoorlydrainedsoilsduring rainy seasons (Figure 1.4).

Figure 1.3. Distribution of solids, air, and water in a compacted soil.

Air15%

Water15%

Mineral69%

Organic1%

2

Figure 1.4. The effective use of raised beds in a garden setting.

Organic Material

The best soil amendment to reduce the risk of soilcompactionandsoilcrustingistheadditionandmainte-nanceofhighlevelsoforganicmatter.Goodsupportingevidenceforthispracticecomesfromobservingcharac-teristicsofsoilswithextremelydifferentorganicmattercontents.SoilsofthedesertsouthwestUnitedStatesarehardwhendry,stickywhenwet,andformcrustsimpen-etrable to the germinating seeds of lettuce and carrots.These soils characteristically have less than 1% organicmatterinthesurfacelayer.Incontrast,soilsdevelopedincoolerclimatesoftheupperMidwesttypicallycontain3%to5%organicmatter,arelesslikelytobestickywhenwet,hardwhendry,orformacrustthatsmallseededplantscannotpenetratewhentheygerminate.Thekeyislotsoforganic matter in the soil. The greatest benefit of organic gardeningistheimprovedeasewithwhichsoilscanbe

managed. The greatest drawbacks are finding enough organicmatterandmanagingitinsuchawaythatotherproblemsarenotcaused.Soilorganicmattermaintenancewillbeconsideredinlaterchapters.

Life in the SoilInadditiontoknowingthegeneralmakeupofsoils,

proper management of the soil involves understandinghow the soil lives, that is, how it responds to changes.Mostofthissoillifeisaresultofchemicalandbiologicalactivityinthesoilthatiscloselylinkedtotheamountoforganic matter and clay present (Figure 1.5). Although muchof thesoil iscomposedofsandandsiltparticles,theyareratherinertorinactiveintermsofsoillife.

is responsible for their tremendous adsorptive proper-ties. Clay (and organic matter) gives soils their capacity to storewaterandnutrients forplants.Becauseofhowtheywereformed,clayshaveaninternalelectricalchargeimbalance that causes them to act like the negative (-) poleofamagnet.Thischaracteristicaddstotheiradsorp-tive properties, especially for chemical elements in thesoilthatarepresentaspositivelychargedions,orcations.Someof theseareessentialelements thatplants requireasnutrients.Theplate-likeshapeofclayparticlescanbeenvisionedasshowninFigure1.6.

Figure 1.5. Illustration of soil minerals (sand, silt, and clay); organic matter; pore space; and microorganisms (from Scheyer and Hipple, 2005 Urban Soil Primer).

Water Air space Sand

Silt

Fungal hyphae

Clay-organicmatter complex

Clay

Bacterium

mi

l

f

f

jkk

Soil Colloid

Figure 1.6. Negative charges on clay or organic col-loids attract cations to their negative charges.

K+ Ca2+

NH4+

Mg2+Na+

Ca2+

3

Clay

Clays are a unique and critical component of soilsbecause of their size, shape, and electrical charge. Clayparticlesaresosmall theycanonlybeseen throughanelectron microscope and belong to the category of par-ticlescalledcolloids.Theseparticlesaresmallenoughtobe suspended in fluids almost indefinitely. A common example ismilk.Thesolidsremainsuspendeduntil themilk sours, causing the particles to coagulate, or cometogether in largegroups thatsettle to thebottomof thecontainer. The solids in smoke are colloidal, allowingdense smoke to be seen, and easily moved by wind asthesolidsaresuspendedinair.Clayiseasilysuspendedincleanwater.Thesuspensionofclay fromtheerosionofPermianRedBedgeologicalmaterial(parentmaterialfor many soils) in Oklahoma is likely the reason the river betweenTexasandOklahomawasnamedtheRedRiver.

Clay particles usually have a thin, irregular shape,sometimesreferredtoasplatey.Thisshapeandsmallsize

Here Comes the Gypsum

Itmayseemlikethisdiscussioniswanderingawayfromworthwhileapplicationsofinformationtohelpthegarden or lawn, but there is a point to it all. There aresituations in the urban landscape when gypsum addi-tions are beneficial to the soil. These situations are a result of the soil receiving excess sodium (chemical symbol Na) caused by salt water spilling onto the soil (recent or past), potassium (K) from excessive dumping of fireplace ashes inanarea,orasaresultof irrigatingwithhighsodiumwater. When this happens, because Na and K are posi-tivelycharged ions (Na+andK+) that have a thick shell ofwateraroundthem,theycannotgetcloseenoughtotheclay toeffectivelyneutralize thenegativechargeontheclay.Asaresult,theclayparticlesaresaidtobedis-persed, that is, they are no longer grouped together inaggregates, and are free to float about and plug up the small pores in soil responsible for water infiltration and drainage.Whenthishappens,weobservewaterpuddlesafteronlya smallamountof rainor irrigation.Becausethesoilporesprovidedbysandandsoilaggregatesareplugged, water does not reach the roots and plants dieofdroughteventhoughthesurfacesoilisverywet.Thisconditionisreferredtoasasodicoralkalisoil.

Wemaypicturethesodicsoilconditionmuchaswhatwould happen if we filled a bath tub full of water and then threwplayingcards,onebyone,intothetub.Astheysettledtothebottom,somewouldslideoverthedrainholeandrestrictorpreventwaterfromleavingthetub.Thecardswouldplugthebathtubdraininmuchthesamewayclayparticlesinasodicsoilwouldplugsoilpores.However,ifweputarubberbandaroundthedeckofcardsandthenthrewthemintothetubitisunlikelythedrainwouldget

plugged.Infact,wecouldthrowmanydecksofcardsintothetub,ifthecardsofeachdeckwereboundbyarubberband,thetubwouldstilldrain.Dispersedclayinasodicsoilcanbebroughtbacktonormalfromaliberalapplica-tion of gypsum (50 to 100 lbs/1000 sq ft) if good internal soil drainage is provided. The calcium (Ca) in gypsum (cal-cium sulfate) will dissolve in the soil slowly, and because thecalciumionhastwopositivecharges(Ca2+) compared toonlyoneforeithersodiumorpotassium,calciumwillbumpsodiumoff the clayandeffectivelyneutralize thenegativeclaychargesallowingtheseparatedclayparticlestocomebacktogetheringroupsorpacks.Theprocessismuch the same as gathering the individual cards in thetub intodecksandputtingarubberbandaroundthem.Doingsowouldallowthetubtodrainfreely,providedthewaterhadsomewheretogo.Similarly,goodsoildrainageisnecessarysotheexcesssodiumcanbewashedoutofthesoil (Figure 1.7).

Ca2+

Ca2+

Ca2+

————

g CalciumSaturated

Clayparticlesbound,excesssodiumleachesout

Figure 1.7. The action of gypsum to restore dispersed sodic soil to more aggregated normal soil.

Na+Na+

Na+

Na+

Na+

Na+

— — — —

— — — —

+Gypsum(Calcium Sulfate)isadded

SodiumSaturated(15%)

Clayparticlesseparated,canplugsoilpores

organic matter (even humus) promoted by cultivation willoutweightheinputfromplantsgrowninthegarden.Organic gardeners realize that if they cultivate the soilfrequently,theymustbringmoreorganicmaterial(grassclippings, compost, etc.) from other sources to maintain a suitablyhighhumuslevelinthesoil.

Increasing the organic matter from the 1% levelcommonincultivatedOklahomasoils,to3%to5%willcauseclayeyandsandysoils toactmore like loamtex-turedsoils.Theclayeysoilswillnotcrustandgethardwhendry,thesandysoilswillbeabletostoremorewaterandnutrientsifanadequateamountoforganicmatterispresentinthesoil.

An often asked question by gardeners is how muchand what types of organic matter are good. Specific, quan-titative answers to these questions are difficult to make. Generally, it is good to use a variety of organic sourcesand add them in moderation (another nonspecific term).

Moderation,inthisuseoftheterm,meansdonotaddmoreorganicmaterialatanyonetimethanyoucanphysicallyincorporate(spadeortill) and still end up with a surface that looks morelikethesoilthantheorganicmaterialjustadded.Addingavarietyofsourcesmeansjustthat. Almost anything organic can be added,including shredded newspaper, table scraps,plant trimmings from flower beds and shrub-bery, grass clippings, animal waste, compost,etc.Thetwocautionsingoodmanagementare1) do not use just one material, and 2) do not try toconvertasoilwith1%organicmattertoonewith5%organicmatterovernight (donot tryto create an instant organic garden). Too much compostoranimalmanureappliedtothesoilmay result in high soil salinity or too manynutrientsthatmayimpactplantgrowth.

Having just moved from Michigan to Arizona (Tucson), a new homeowner decided to improve the existing rock yard and develop a garden. Believing in the value of soil organic matter, and knowing the pale, mineral desert soils of Arizona would be incapable of providing the good foundation for new plantings, thehomeowner purchased two pick-up loads of bagged steer manure and spread it on the small garden-to-be area. Much to his dismay, the homeowner could not grow anything in the garden for a year because he had added so much steer manure to the small area that it responded more like a compost pile than a garden. Whenever it was moist enough the high desert temper-ature caused very active microbial decay of the steer manure. This in turn created more heat in the soil-steer manure mixture and it released more available nitrogen than plants could use. His neighbors kept looking for steers.

Chapter 5 will examine the importance of organicmattermaintenanceinrelationtonitrogenmanagement.

4

Soil Organic Matter

Assoilclayisusuallythefocalpointofsoilchemicalactivity,soilorganicmatterisusuallythefocalpointforsoilbiologicalactivity.Thisbiologicalactivityresultsfromtheactionofmicroorganisms,mainlybacteria,fungi,andactinomycetesthatarepresentinvirtuallyallsoils.Thesemicroorganismsaremicroorsmallorganisms.Theyhavemanyofthesamerequirementsforgrowthastheplantswearetryingtogrowinthegardenorlawn.Theyneedwater, heat (warm temperature), and most of the mineral elements of higher plants. Additionally, most of themneedorganicmaterialasasourceofcarbonandenergy.These microorganisms decay plant residue and convertittohumus.Mostofthemareaerobicthatistheyrequireoxygenfromsoilair.

Organic matter management, in organic gardening,depends on the balance between how much organicmatterisaddedandhowmuchislost.Rootsandabovegroundplantpartsareanatural inputoforganicmate-rialtothesoil.Ifthegardeniscultivated,however,theseadditions are inadequate to raise, or even maintain,soilorganicmatter levelsbecause thedecayand lossof

What is pH?Good nutrient and soil management often involves

obtainingarepresentativesoilsampleandsubmittingittoalaboratoryfortesting.AcommonsoilpropertytestedbylabsisthesoilpH.Itisaninventionofchemists,anditisausefulindicatorofwhetherthesoilisacidicorbasic/alkaline.Tounderstandthis,considerthefollowing.

Mosteveryoneisfamiliarwiththechemicalnotationforwater,H2O,saidH-2-O.Thisdesignatesthatwaterismadeupoftwohydrogenions(H+) and one oxygen ion (O-). Water could also be correctly written as HOH (there would still be two Hs and one O). When pure water is closelyexamined,itisfoundthatasmallamountofithasbroken apart (chemists call it dissociated) into pieces of hydrogen and oxygen that have positive and negativecharges on them. This breaking apart can be expressedas

HOHgH++OH-

WhensubstancescontainingwaterhavealotofeitherH+orOH-inthem,theyarefoundtobemorereactive.Forexample,waterthathasmorethanthenormalamountsofeitherH+orOH-willcorrodemetalsmorethanwouldpurewater.SolutionscontainingmorethannormalamountsofH+ (compared to pure water) are said to be acidic or acid, andiftheycontainlessthannormalamountsofH+theyare called basic or alkaline. Pure water, because it con-tainsthenormalamountofH+,isneitheracidicnorbasicandiscalledneutral.

The amount of H+ present in pure water is only0.0000001 mole per liter, a unit used by chemists. This,andsimilarmeasuresoftheH+present,arecumbersometocommunicate.Aneasierwaytoexpressthevalueisasapoweroften,asdonewhen10x10isexpressedas102or10squared.Thevalueof0.0000001couldbewrittenas10-7.Thiswassoonshortenedtojustwritingthenumberto which 10 was raised (7) and indicating that it was a negativevaluebyusingthesmallletterp.SinceH+wasbeing measured (or expressed), pH came to mean the negative power to which 10 is raised to express the H+concentration.ThescaleofpHisfrom0to14.Forpurewaterthen,thepHis7.WhenthepHislessthan7itisacidicandwhenitisgreaterthan7itisbasicoralkaline.ItisimportanttorealizethatapHof5is10timesmoreacidicthanapHof6and100timesmoreacidicthanapHof7.KnowingthishelpsusunderstandwhysoilpHdoesnotchangerapidlyfromoneyeartothenext,unlessweadda largeamountofabasicmaterial, like lime,oranacidicoracidproducingmaterial,likesulfur.

Normal Occurrence of Acid and Alkaline Soils

Whethersoilsarenaturallyacidicoralkalineisrelated

to annual rainfall more than any other single factor. Incentral and eastern Oklahoma, which receive over 30inches of rainfall annually, soils are commonly acidic.InwesternOklahomawhereannualrainfallaverages20inchesorless,soilsarenormallyneutraloralkaline(pH7 or greater). Soils are neutral or alkaline when the basic, or lime-like,materials fromwhichtheydeveloparenotwashedoutbyhighrainfall.Insomewesternsoilsthereis just enough rainfall to cause the parent material tochemically weather (gradually dissolve in water), but not enough rainfall to wash the products away.Accumula-tionoftheseproductsresultsinwesternsoilscontaininggypsum (calcium sulfate) and lime (calcium carbonate) at ornearthesoilsurface.Evenunderintensivegardening,and soil management practices that promote increasedsoilacidity,thesesoilswillremainneutralorbasicinpHfor several generations. Typical soil pH and associateddescriptivetermsareshowninFigure2.1.

Chapter 2Acid and Basic Soils: pH

Figure 2.1. Typical pH found in soils and terms used to describe them.

Strong

Medium

Slight

Slight

Moderate

Medium

Strong

Very Strong

Acidic

Basic

MostProductive

9.0

8.0

7.0

6.0

5.0

4.0

Ammoniacleaner

Pure water

VinegarLemon juice

5

Changing Soil pH

Acid Soils

Sometimes the soil is too acidic for normal growthof landscape or garden plants (Figure 2.2). In these cases limecanbeaddedtoneutralizesomeoftheacidityandmakeamorefavorableenvironmentfortheplants.MostplantswillnotdowellwhenthesoilpHislessthan5.5,andtheydopoorlywhenthepHis less than5.0.Someexceptions are acid loving plants (more appropriatelytermed acid tolerant) like blueberries, azaleas, pin oak, andfescue.

an indicationof thesizeof the largereservoirandhowmuch lime is necessary to fill it up to where it will change thepHtothedesiredvalue.

Whenmanagingacidsoils,soilpHisusedtodecidewhetherornottolime;bufferindexisusedasaguideforhowmuchlimetoadd.Forthisreason,whensoilpHis6.3orhigher,bufferindexisnotmeasuredbecausethesesoilsshouldnotbelimedformostplants.

Table2.1showstherelationshipbetweensoilbufferindexandlimerequirement,forlimethatisabout100%active ingredient.Typicalaglimemayonlyhave60%ofactive ingredient; therefore, more may be needed if thelime used is less than 100%. Additional lime may beadded the followingyearafteranewsoil test indicatesthesoilisstilltooacidic.

Figure 2.3. Relationship between soil pH and buffer index for sandy and clayey soils.

7.06.56.05.55.04.5

7.06.96.86.76.6

7.06.86.66.46.2

pH

pH

BI

BI7.06.56.05.55.04.5

Sandy

Clayey

Table 2.1. Calibrated relationship between soil buffer index (BI) and lime requirement.

Buffer Index Lime Needed Lime Needed lbs/1000 sq ft tons/acre

7.1 or greater 23 0.5

7.0 32 0.7

6.9 46 1.0

6.8 55 1.2

6.7 64 1.4

6.6 87 1.9

6.5 115 2.5

6.4 142 3.1

6.3 170 3.7

6.2 193 4.2

6

Figure 2.2 This is the impact of low soil pH on canola. The forefront is more acidic than the background.

Once a soil test identifies a soil as too acidic for normal plantgrowth,thenextstepistodecidehowmuchlimetoapply. Most soil tests will report a buffer index (BI), or somemeasureofthesoilscapacitytoholdacidicandbasicmaterials. Because both acidic and basic materials heldinthesoilexistascations,whicharechemicalelementsthathaveapositivechargelikeH+,theabilityorcapacityofthesoiltoholdthesesubstancesisdirectlyrelatedtotheamountofnegativechargesinthesoil.RecallingfromChapter 1 that clay particles have an internal negativecharge,claysthenserveasareservoirforholdingacidicandbasicmaterialinsoil.Additionally,sincehumusalsohasnegativechargesatthesurfaceofparticles,thehumuscontentofsoilalsocontributestohowmuchacidicandbasicmaterialthesoilcanhold.

The soil’s ability to resist change in pH is oftenreferred toas itsbuffer capacity.Andso, themore clayand humus in the soil the greater its buffer capacity.Sandysoilstakeonlysmallamountsoflimetoneutralizethe acidity present, whereas clayey soils containing alotoforganicmattermaytaketwotothreetimesmore.Figure2.3illustratestherelationshipbetweensoilpHandbufferindex.Thebuffercapacityofthesoilisdepictedasalargereservoirthatholdsbasic,lime-likematerialthatis connected by a small conduit or pipe to a small res-ervoirwherepHismeasured.WhenpHismeasured,itidentifies the levelofacidityinboththesmallandlargereservoirs (since they are connected). Buffer index gives

Becauseacidisheldontheexchangesites,ortheneg-ativelychargedsurfaceofclayandhumusparticles,limemustbemixedwellintothesoilinordertoeffectivelyneu-tralizesoilacidity.Themixingisbestaccomplishedwhenboththelimeandsoilaredryandinapowderystate.

This condition is not usually possible (and makingthe soil into a powdery condition is not usually desir-able), but good mixing will hasten the reaction of lime and soil. For established lawns, mixing is not possible,butlimingafteraerationwillhelpthelimepenetratetherootingzone.OnceliminghasbeendoneandthesoilpHisraisedtoamoredesirablelevel,itshouldnotbeneces-sarytolimeagainforseveralyears.

Basic or Alkaline Soils

Whensoilsaredevelopedfrombasicparentmaterial(limestone) or in low rainfall climates, the pH is usually above7.Althoughitisusuallytooexpensiveforfarmersto amend their fields to lower pH, homeowners can con-siderthisasanoptiontoallowacidlovingplantsinthelandscape. For small areas, like portions of flower beds or gardens, the first approach should be to remove the existingsoil,unlessitisalreadyverysandy.Itisonlynec-essarytoremoveexistingsoiltoadepthofaboutafootformostplantings,foritisinthetopfootofsoilthatmost

active roots will reside (slightly greater depth is desir-able for trees). Once existing soil is removed, it should be replaced with top soils with desirable properties. If thepHisnotacidicenough,yellowsulfurcanbeaddedtofurtheracidifythesoilaccordingtoTable2.2.Theyellowsulfur is oxidized to sulfuric acid (battery acid) by existing soilmicroorganisms,butwilltakeseveralweekstocom-plete. It will usually be best to add small amounts ofsulfurandperiodicallycheckthepHtograduallydevelopthedesiredsoilpH,thusavoidingtheriskofaddinganestimated largeamountofsulfurandendingupwithasoilpHtooacidictogrowanythingin,andthenhavingto lime the soil. The difficulty with making the soil more acidic is that thematerialsweusedo nothaveadesir-able end-point pH, which is when the material is donereacting.Thus,whileexcesslimeisusuallynotharmfulandwouldresult inthepHgoinguptoonlyabout7.5,excesssulfurcouldbringthepHdownbelow4.0.

Table 2.2. Estimated amounts of sulfur required to acidify alkaline soils.

Existing pH lbs sulfur/100 sq ft

7 to 8 2

8.1 to 8.5 4

8.6 or above 6

7

8

Plants and their Environment: Plant Growth Factors

General Considerations

There are several aspects of the landscape environ-ment that influence how well plants grow. The most obviousofthesearelight,heat,moisture,andnutrients.

Plantings are sometimes made because of their tol-erance or need for light or shade and sometimes thelight condition is modified to create a better light con-ditionthanexists.Forexample,fescueturfisplantedinshadewherebermudagrassdoespoorly.Asalreadydis-cussedinChapter1,themoisturesupplytoplantscanbeadversely influenced if the soil is compacted, but usually improvedbyincreasingthehumuscontent.Heat,mois-ture, and nutrients for plants can all be influenced by the landscapeandbysoilmanagement.Whenthelandscapeis not flat, subtle differences in relief can cause big differ-encesinhowplantsrespond.Forexample,soilonslopesusually will be drier than soil in level areas above andbelowtheslope.Soilat thebottomof theslopemaybewetforlongerperiodsoftimethanthatontheslopeorabovetheslopeasillustratedinFigure3.1.

Usuallytheareathatwascutwillhaveashallowsur-facesoilthecontractorbroughtin,underlainbycompacted,infertile subsoil. It will be difficult to grow anything deeper rootingthanturfonthecutarea.Whenplantsdonotgrowwellitisoftenenlighteningtodigorprobeintothesoiltodetermine if adequate subsoil depth exists. Occasionallytherestrictivelayerisaburiedpieceofplywood.

The growth factor easiest to manage is that of thenutrientsupplyforplants.Forthisreason,theremainderofthishandbookwillbedevotedtothattopic.

Essential Elements for PlantsPlantsdifferingrowthhabit,morphologicalfeatures,

and benefit or purpose they serve the homeowner, how-ever, all plants require 16 chemical elements (Figure 3.3) tosurviveandreproduce.Nomore,noless.

Thenamesofthe16essentialelementsandtheirchem-icalsymbol(oftenusedintrademagazinesandproductinformation) are listed in Table 3.1. While it is important to recognize that only 16 elements have been identified by modernscienceasessentialforplants,mostofthemarewellsuppliedinthegrowthenvironmentandonlyafewrequire our management. Based on the amount neededthosenutrientsaregroupedinmacronutrients,secondarynutrients,andmicronutrients.

Chapter 3Growth Requirements for Landscape Plants

Figure 3.1. General relationship of landscape posi-tion and soil moisture.

Figure 3.2. Areas of cut and fill for reshaping landscape.

Moist

DryWet

Because water is a good conductor of heat, butrequiresmoreenergytowarmupthandoesdrysoil,wetsoilstendtobethelatesttowarmupinthespringcom-pared to moist or dry soils. Improving the drainage ofsoilsatthebottomofslopescanhelpthemwarmupatthesametimeastherestof the landscape.Newhomesitesare sometimes leveled by cutting earth away from thehigh points and using it to fill the low points on the lot, as showninFigure3.2.Thiscanbedrasticinsomecasesandresultinthenewsurfacesoilbeingquitedifferent.

Cut

Fill

Figure 3.3. Essential nutrients needed by plants.

16EssentialElements

C H O

B Cl Cu Fe Mn Mo Zn

N

P

K

Ca

Mg

S

Macronutrients

Carbon (C), Hydrogen (H), and Oxygen (O)

HigherplantsgettheirCfromcarbondioxide(CO2) in theatmosphere.MostoftheHandOforplantsissuppliedbywater(H2O) and air (O2). Timely irrigation and man-aging soil to maintain or improve infiltration and internal

9

drainage (as discussed in Chapter 1) can be important to meeting plant needs for these elements. In many homelandscapes,perennialplantshavebeenwiselyselectedtothriveinthenaturalclimateandsoilofthesite.Whenthisisdone,littleaddedmanagementisnecessary.

Nitrogen (N), Phosphorus (P), and Potassium (K)

The other three nutrients that are required in largeamounts by plants, hence called macronutrients, arenitrogen, phosphorus, and potassium. Because thesenutrientsareprimarilysuppliedfromthesoil,theywerethe first elements to become depleted under intensive croppingsystemsthatresultedinhighyieldsofproducebeing hauled off the fields to market. In response to wide-spread soil depletion, the fertilizer industry was born.Subsequently, soil supplies have been replenished byadditionofminednaturaldepositsorsyntheticallypre-paredsolubleformsofthesethreenutrients.

Plant growth and yield are strongly influenced by the supply of N. Of all the nutrients, N is most commonlydeficient, especially when plant vegetation is removed from the area where it grew (bagging lawn clippings). Because nitrogen is bound organically in amino acidsand plant proteins, when plants die, much of the N inthe dead tissue remains bound in these organic forms.Asplantresiduedecaysandbecomessoilorganicmatter(humus) most N remains organically bound and becomes

an important reservoir of slow-release N. Nitrogen inhumuscannotbeabsorbedbyplantsuntil it isreleasedbysoilmicroorganismsandisthenavailableinaninor-ganicformaseitherammonium(NH4

+) or nitrate (NO3-).

Clearly, nitrogen management must involve organicmatter management. Understanding this is especiallyimportantfororganicgardenersandwillbedealtwithingreaterdetailinlaterchapters.

Phosphorus deficiency in mature lawns and gardens isuncommonbecauseplantsuseonlyaboutaneighthasmuch phosphorus as they do nitrogen and many hom-eowners apply as much phosphorus back to the soil intheformofcompostandfertilizersastheydonitrogen.Sincephosphorusisimmobileinthesoil,itaccumulatesandwillbeadequatelysuppliedbysoilsthathaveahis-toryofannualinputsofphosphorus.Phosphorusmaybedeficient in soil that was previously farmed and received littleornophosphorusinput.Phosphoruswillmostcom-monly be deficient in recently modified landscapes (such as the cut area illustrated in Fig. 3.2) where surface soil has been removed and the P deficient subsoil is being usedasagrowingmedium.

Potassium deficiency is common in high rainfall (greater than 35 inches annually) regions, such as eastern Oklahoma. Soils that naturally have a near neutral orhigher pH (7 or above) will usually be rich in available potassium (western Oklahoma) because they have devel-oped in arid and semi-arid climates without enoughrainfalltoleachpotassiumfromthesoils.

Table 3.1. Essential nutrients required by plants.

Element Name Element Symbol Soil Mobility*

Macroutrients Carbon C Hydrogen H Oxygen O Nitrogen N M Phosphorus P I Potassium K I

Secondary Nutrients Calcium Ca I Magnesium Mg I Sulfur S M

Micronutrients Iron Fe I Manganese Mn I Copper Cu I Zinc Zn I Boron B M Chlorine Cl M Molybdenum Mo I* M means the nutrient is mobile and will move with water in the soil; I means the nutrient is relatively immobile and does not move with water in the

soil readily.

10

Secondary Nutrients

Calcium (Ca), Magnesium (Mg), and Sulfur (S)

These elements are seldom deficient in the urban landscape (Figure 3.4). Calcium and magnesium are the mainelementsresponsibleforkeepingthesoilpHfrombecoming too acidic. Before supplies for plants becomedeficient, the soil pH is too acid for plants to grow and limemustbeaddedtoraisethepHbacktoasuitablelevel.Becauselimeismostlycalciumcarbonate(usuallysomemagnesium carbonate), liming to keep the pH desirable alsomaintainsgoodsuppliesofcalciumandmagnesiumforplants.

RainfallinOklahomaaddsabout6lbsofsulfurperacreperyear.Whilethismaynotseemlikemuch,plantsonly require about one-twentieth as much sulfur asnitrogen.Oneway toappreciatehowmuchsulfur is inrainfallistoconsiderthelikelihoodofneedingfertilizernitrogenifwereceived120lbsperacreofnitrogeneachyearinrainfall.Thiswouldbeequivalenttoabout3lbsofnitrogenper1000sqft,morethanenoughtosupportsummergrowthofa lawn. If sulfur isneeded,gypsum(calcium sulfate) would be a good, inexpensive source.

Micronutrients

Molybdenum (Mo), Manganese (Mn), and Copper (Cu)

These elements have not been found to be deficient in Oklahoma soils, and are unlikely to be deficient in land-scapeplantsgrowninsoilorsoilmixes.

Chlorine (Cl) and Boron (B)

Chlorine deficiency has only been documented once byOSUresearch.ThisoccurrednearPerkins,inwheatonadeep,sandysoilfollowinganunusuallywetyear(chlo-rine likely leached out of the soil). Boron deficiency also occurs in deep sandy soils and has only been reportedin peanut production in Oklahoma. It is unlikely hom-eowners will experience deficiencies of either of these nutrientsintheirlandscapes.

Iron (Fe) and Zinc (Zn)

Deficiencies of iron and zinc are limited to specific soil-plantconditionsorsituations.Theplantsmostsus-ceptible to zinc deficiency in Oklahoma are pecans. Commercialgrowersroutinelyapplyfoliarzincfertilizersto avoid the problem. Deficiency shows up as a shortening of internodes (space along stem between nodes or leaves) calledrosetting,whichcauses the leavesorbranchesofnewgrowth toappearas if theyareallgrowingoutofthesamepointonthemainstalk.Cornisthesecondmostsusceptible plant to zinc deficiency. Most soils in Okla-homaareadequatelysuppliedwithZn.

Mostsoilscontain50,000to60,000lbsperacreofiron.However,mostofthisironisinanoxideform,likerust,that plants are unable to use directly. Iron deficiency in plants is limited to high pH soils (central and westernOklahoma) and in plants that do not have an effective mechanism for extracting iron from soil. These plantsare unable to acidify soil next to their roots, therebyincreasing availability of iron, and may be termed acidloving.Susceptibleplantsmayalsolacktheabilitytopro-ducecompoundsfromtheirrootscapableofchelatingFeto improve its availability. Chelate comes from a Greekwordmeaningclaw.Ametalionisboundwithpartsofalargeorganicmolecule,whereindividualbondsbetweeneachpartoftheorganicmoleculeandthemetalcausethemetaltobeheldasifitwereinthegripofaclaw.PinoaksareanexampleofplantsthatdopoorlyinneutralandhighpHsoils,andtheyarenotrecommendedforpartsofcen-tralandwesternOklahomaforthatreason.Mostgardenplantsareeffectiveinobtainingadequateironfromsoilsand iron deficiency is not common (Figure 3.5).

11

Figure 3.4. Example of a properly nourished and maintained landscape.

12

When iron deficiency does occur, it will appear as interveinal chlorosis (yellowing between the veins) in the newestleavesbecauseironisnottranslocatedwellfromold leaves to new leaves, as are N, P, and K. Deficiencies can be corrected by foliar application of a 1% solutionofironsulfate,iron-ammoniumsulfate(ferrousorferricammonium sulfate), or other fertilizers containing Fe. However,ifthesupplyofironfromthesoiltotheplantisnotimproved,chlorosiswillagaindeveloponnewgrowthbecauseironisnottranslocatedfromold,wellfedtissue,to new deficient tissue. Soil organic matter helps to natu-rally chelate ironand improve its availability toplants.Improvingandmaintaininghighorganicmatterlevelsinthesoilusuallyreducesoreliminatestheproblem.Also,periodic surface application of yellow sulfur will makethesoilacidicandreducethechanceofironchlorosisifthesoilishighinpH.

Figure 3.5. Example of crepe myrtles that are not exhibiting any micronutrient deficiencies.

Plant Nutrient Uptake Patterns

Mobile and Immobile NutrientsTherearemanywaystogrouptheessentialelements

in relation to their chemistry and plant need, such ascations or anions, whether or not they can be chelated,whethertheyformsolubleorinsolublecompounds,etc.Fromthestandpointofmanagingthenutrients,however,theirmobilityinthesoilhasbeenthemostusefulchar-acteristic.Oneofthemostmobilenutrientsinthesoilisnitrogen and one of the most immobile is phosphorus.Potassiumisintermediateinmobility.Relativemobility,onascaleof1to10,forthesethreenutrientsisillustratedinFigure4.1.

Figure 4.2 shows that nitrogen, which commonlyoccurs as nitrate, can be utilized from the soil that isbeyond the reach of the longest roots. This is becauseas theplantextractswater fromthesoilnext to its rootsurfacesandthatsoilbeginstodryout,waterfromsur-rounding moist soil moves into this region of dry soilnext totheroot.Someofthismovement is theresultofawick-likeactionwithinthesoil.Aswatermovestotherootsurfaceitcarriesnitrogenwithit.

Whenseveralplantsaregrowinginanarea,suchasa row in thegardenorat random in the lawn, thevol-umes of soil, from which they each can draw nitrogen,overlap (Figure 4.3). In this volume of soil, plants are competingforthesamenitrogen(orwater,sinceitisalsoa mobile nutrient source). As more and more plants are crowdedintoanarea,competitioncontinuestoincrease.Ifthenitrogensupplyfromthesoilwasadequatetosup-port normal growth for one plant, without competitionfromotherplants,thenwithasecondplantnearbycom-petingfornitrogen,morenitrogenisneeded.Ifadditionalnitrogenisnotadded,growthwillbelimitedtolessthannormal. From this illustration we learn that as yield ofplant material (lettuce, corn, spinach, grass clippings, etc.) fromanareaisincreasedthedemandformobilenutrientslikewaterandnitrogenalsoincreases.Inotherwords,thecompetitionamongplantscanbereducedoreliminatedbyaddingmoreofthenutrient.

The above concept for mobile nutrients is veryimportant because it clearly shows that good nitrogenmanagementbeginswithayieldgoalorestimateofhowmuchistobegrowninanareainagivenperiodoftime.Forbermudagrasslawnsthatreceiveadequatewaterinthesummer,addingnitrogenattherateof1lbper1000sqftper

Chapter 4 Gas and Oil for the Garden and Lawn

Figure 4.1. Relative mobility of the major plant nutri-ents supplied through the soil.

Moves easily Nitrogenwith water 10 (nitrate nitrogen)

3 Potassium

Little movement with water 1 Phosphorus

Mobile Nutrient Uptake by Plants

Thewayplantsextractnutrientsfromthesoildependsonhoweasilythenutrientsmoveinsoilwater.Uptakeofmobilenutrients,likenitrogen,isshowninFigure4.2.

Figure 4.2. Volume of soil (shaded area) mobile nutrients, such as nitrogen, can be absorbed from by plants.

Figure 4.3. Competition for mobile nutrients (nitrogen and water) among plants growing close together.

13

monthwillnormallysupportgrowthwithagoodgreencolor thatwill requiremowingonceor twiceaweek. Iftwotothreetimesthatrateofnitrogenisavailabletotheturf,itwillrequiretwiceasmuchmowingbecausecom-petitionamongplantswillbemuchlessandgrowthwillbedoubled.So,ifwaterisnotlimited,mowingfrequencycanberegulatedbynitrogensupply.Similarly,nitrogendeficiency is often a result of rapid growth rate (promoted by the growth environment) and/or high yield of plant materialwhenthesupplyofnitrogenismarginal.

Immobile Nutrient Uptake by Plants

Nutrientsthatdonotreadilymoveinthesoilaswatermoves,aretakenupdifferentlythanmobilenutrientsbyplants.Uptakeof immobileplantnutrientsoccurs fromonlyathincylinderofsoilimmediatelysurroundingtheroots (Figure 4.4).

management of immobile nutrients is not dependentonorrelatedtoyieldlevel.Ifthesoilcapacitytosupplyphosphateisadequatetomeettheneedsofonecornplanteverytwofeetofrow,thenitwillalsobeadequateifthereisfourtimesthatnumberofplantsintherow.

When a phosphorus deficient soil is fertilized, and thephosphatefertilizer is tilledin,onlyasmallportionof the fertilizer (10% to 15%) will be in a position where rootsmaycomeincontactwithit.Sinceitdoesnotmovewithwater in the soil,mostof the fertilizerwill slowlyreactwiththesoilandaddtophosphorusalreadyinthesoil (Figure 4.6). If fertilizer is added each year, there will be a gradual build up of soil phosphorus until finally the phosphorus availability throughout the soil (soil test P) willbeadequatetosupplytheneedsofwhateverplantsare being grown. Because phosphate is so immobile insoil, it is not effective when applied to the soil surfaceduringthegrowingseason,unless,asinthecaseofber-mudagrasslawns,theplantroots(suchasbermudagrassrhizomes) are close to the surface.

Figure 4.4. Volume of soil (shaded area) that immo-bile nutrients, such as phosphorus, can be absorbed from by plants.

Figure 4.5. Lack of competition among plants for immobile nutrients.

Compared to uptake of nitrogen, only soil from asmall volume of the plant root zone is used to providephosphorustotheplant.Thevolumeofsoilissosmall,that even when plants are crowded close together, asshown in Figure 4.5, there is little competition amongplantsfortheimmobilenutrientinthesoil.

Since there is nearly no competition among plantsthat are crowded close together to provide high yields,

Figure 4.6. Distribution and plant availability of incor-porated phosphate fertilizer (granules shown around the roots).

14

Knowing When and How Much to Fertilize

Takingcareofthenitrogen,phosphorus,andpotas-

siumneedsofplantsinthelandscapeis,inmanyrespects,liketakingcareofthegasandoilrequirementsforacar(or other internal combustion engine).

Nitrogen for Plants is like Gas for an Engine

If a lawn mower is to be used for several hours ofmowing,theengine’sgasolinetankwillverylikelyneedadditionssometimeduringtheoperation.If,ontheotherhand,themowerwillonlybeusedtotrimthegrassalonga sidewalk leading from the street to the house, addi-tionalgaswill likelynotbeneeded.Whetherornotthelawnmowerengineneedsgasaddedtoitstankdependsonhowmuchmowingwillbedone.

Inasimilarway,nitrogenrequirementsforplantsinthe landscape depend upon how much they will growoveraperiod,andonanareabasis,howmuchgrowthwill occur in a specified area (like 1000 sq ft). So, a bermu-dagrasslawnthatisnotexpectedtogrowmuchatall(andfor which the light green color will be acceptable) will needlittleornonitrogenfertilizer.However,ifthelawnisexpectedtogrowvigorouslyandfrequentmowingisrequired, in order to maintain a medium to dark greencoloritwillneedatleast1lbofactualnitrogenper1000sqfteachmonthofgrowth.

Whenpreparingtomowalargelawn,ormowforanhour or more, the fuel tank may be filled initially. Simi-larly, it isagoodpracticewhenpreparingtoprovideNfor vigorously growing plants, to make sure the plantshaveatleast1lbofactualNavailableper1000sqft(1lbN/1000ft2) of area. Additional N can be added during the growing season if there is enough growth (yield) to use up theinitialsupplyofNandcontinuedgrowthisdesired.Thus for lawns that will grow four or five months, N may needtobeappliedtwoorthreetimesduringtheseason.

SometimesthereisthetemptationtoapplyalltheNrequiredforoneseason,at thebeginningof theseason.Thisissomewhatliketryingtoputallthegasthelawnmowerwillneed,forthreehoursofmowing,intoatankthatcanonlyholdenoughforonehour.Thetankwillover-flow and much gas will be wasted (to say nothing of the risk of starting a fire when the engine is started). Applying excessnitrogendoesnotresultinalloftheexcessbeingwasted,butsomewillbe lostand theremainingexcesswillcauseunwantedrapidlushgrowth,requiringtwotothreemowingaweekifgrowingconditionsaregood.

Because N is a nutrient that is mobile in the soil,surplusNcancauseaproblemofundesirableexcessivegrowth,promote or encourage disease,or contribute tothepollutionofsurfaceandgroundwater.Continuedveg-etativegrowthispromotedandfruitingdelayedinsomeplantswhenexcessnitrogenisavailable.Examplesofthis

aretomatoesandokra.Excessnitrogenwillresultincon-tinued vine and leaf growth, but few tomato sets; okrawill be tall and leafy, but with few fruit sets. For theseplants it is important that they have enough nitrogenavailableearlyintheseasontodevelopreasonablysizedplantswithcapacitytocapturethesun’senergyandman-ufacturefoodtodevelopthefruit.AllowingtheplantstorunshortofNmidseasoncausestheplanttobeginfruitset (theplant thinks it isgoingtostarveanddecidestohurry up and provide for its off-spring before it dies).

Nitrogen Deficiency Symptoms

Managingfuelforalawnmowerbecomesrelativelyeasywithalittleexperience.Itmaybeamatterassimpleas just filling the tank on the mower each time before beginningtomowif the job issmallenoughthat itcanbecompletedwithoutrunningoutoffuel.Ifthemowingjobislargeenoughtorequirerefueling,theneedforre-fuelingcanbegaugedbyhowlongtheenginehasbeenused, a fuel gauge, or the experience of running out ofgas. Running out of gas is sensed by the spitting andsputteringoftheengine.Ifweknowwhattolookfor,wecanalsotellwhenplantsarerunningoutofnitrogen.Thesymptoms of nitrogen deficiency are:

1. Poororslowgrowth2. Lightgreencolor3. Yellowing (chlorosis) of the oldest leaves, begin-

ningatthetipandproceedingalongthemidribtowardthebase,orstalk

The first two symptoms are difficult to recognize if healthy plants are not nearby for comparison (e.g., auniform lawn that is moderately deficient will not grow much and will not be dark green, but may be desirable). The pattern of chlorosis is easy to recognize on largeplants like corn, but difficult to see on small leafed plants likefescue.Nevertheless,thesesymptomscanbeusefulinmanagingnitrogen,becauseunlikethefueltankforthelawnmower,itisnoteasyorconvenienttoidentifyhowmuchavailablenitrogen is in thesoilwhenplantsstartgrowingoraftertheyhavebeengrowingforsometime.

Some plants in the landscape, especially trees andshrubs,haveaslowgrowthrateandproduceonlyasmallamountofnew,nitrogen-containing,growtheachseason.Forthisreasontheseplantsneedverylittlenitrogen,andusually will receive enough from natural soil suppliesandtherun-offorspillageoffertilizerappliedtoadjacentareas,suchaslawns.

Other Mobile Nutrient Excesses

Water,sulfate,boron,andchloridearealsomobileinthesoil.Becauseboronandchloridearemicronutrients,onlyverysmallsuppliesof thesenutrientsarerequiredfor normal plant growth. Above average supplies ofthese nutrients do not stimulate additional growth likenitrogen,instead,theyareusuallydetrimental.

15

A homeowner called wondering what to do to get flowers to grow again in the flower bed after having killed chickweed with borax. A pound of borax had been applied to an area 3 ft x 20 ft. This rate is equiva-lent to 80 lbs of boron per acre. Normal rates of boron for correcting deficiencies in alfalfa and peanuts range from only 0.5 to 2.0 lbs per acre! Rates above 5 lbs per acre are considered toxic and expected to decrease yield. Obviously, the 80 lb per acre rate killed the chickweed and sterilized the soil so nothing else would grow either. The options for correcting this mistake were to wash the boron out of the soil (difficult at best for the clayey soil) by excessive irrigations over an extended period or to remove the contaminated soil to a landfill and replace it with good topsoil (best option). Moral of the story: beware of advice from sources that are not science based (e.g., testimonials from friends and mass media).

The reason some nutrients are mobile in the soil isbecausetheydonotreactmuchwiththesoil,comparedto the immobileelements.Asa result, if theseelementsarepresentingreatexcesstheycancauseasaltproblem,eveniftheelementisnottoxicitself(asboronintheabovestory). Chloride, nitrate, and sulfate are soluble salts because theydonot formsolidseasilywhen they reactwithother ions.Sodiumchloride,commontablesalt, isagoodexampleofasolublesalt.Whenaddedtowater,table salt easily dissolves (the solid disappears) because thesodiumandthechloridewouldratherbesurroundedbywater thaneachother. In fact, thesodiumandchlo-rideholdthewatertightenoughthatplantscannotgetitaseasily,andmaydieofdroughtwhenthesoilissaltyeventhoughthesoiliskeptmoist.Acommonexampleofthisphenomenon,isdemonstratedwhensaltisaddedtowatertoraisetheboilingpointsofoodcanbecookedorprocessedfaster.Thesaltholdsontothewatersoittakesmore heat to convert the liquid to vapor (boil).

Tothehomeowner,wateristhecheapest,mostcon-venientnutrient toadd,andprobably for this reason ismostcommonlyaddedinexcess.Plantsmustabsorbtre-mendousamountsofwaterandkeepverylittleofit.Mostofthewaterabsorbedbyplantsisusedtotransportnutri-entsintoandthroughouttheplant,andtocooltheplant.Unlessyouarereadingthisbookinatropicalrain-forestandplan to continue livingwhereyouare,mostof theplants in your landscape prefer definite periods of drying conditions.Forthatreasonmostoftheplantswillrequiregood surface and internal soil drainage and will sufferduringextendedperiodsofrainorfrequentirrigation.

Unlike the difficulty and inconvenience of checking soil to determine the need for nitrogen, soil moisturecanbedeterminedbyphysical inspection.Usinga longsharpobjectlikeanailorscrewdriver,disturbthesoiltothedepthofmostroots,often8inchesorless,thenlookat and feel the soil. Darker soil below the surface indi-catesmoremoisturethanthelightercoloredsurfacesoil.Ifitcanbeeasilymadeintoaballbysqueezingitinyourhand,thenitcontainsadequatemoistureforthedayandirrigationisunnecessary.Ifthesurfaceoftheballappearswet and glistens then it is too wet and should not be

Figure 4.7. Dipstick used to check oil in engine (H-high, M-medium, L-low).

H

M

L

16

wateredforseveraldays(waitlongerforclayeysoilsthansandy soils). If it cannot be made into a ball because it falls apart (sandy soil) or remains in firm or hard chunks (clayey soil), then it should be irrigated.

For someplantsduringsome timesof theyear, thesoil is a better indicator of when to irrigate than is theplant.Plants thatare intolerantofheatordroughtmayshow signs of wilt during mid afternoon on extremelyhot,windydays,whenevapotranspirationisgreatest.Ifcheckingthesoilrevealsthereisadequatesoilmoisture,thendonotirrigate.Iftheplantsappeartobesuffering,syringing, that is, spraying the plants with a fine mist of waterjustlongenoughtowettheleafsurfaces,willcooltheplantsseveraldegreesandhelpthemsurviveunusu-ally hot weather (this only needs to be done once anafternoon). If the soil already contains adequate moisture, thenaddingmoreatthistimewillonlylessentheamountofoxygenavailablefortherootsystemanddecreasetheplants ability to survive. Obviously, experience in esti-mating when to irrigate and observing plant responsetothedecisionofwhetherornottoirrigate,willhelptoachievewatermanagementsuccess.

Phosphorus and other Immobile Nutrients for Plants are like Oil

for an Engine

Nutrients that are immobile in the soil, like phos-phorus and potassium, need to be managed with thekindofapproachusedtomanageoilforthelawnmowerengine (Figure 4.7). It does not matter whether you are planning to use the lawn mower for one hour or five hours,ifitislowonoil,someshouldbeaddedtobringtheleveluptofullbeforetheprojectisstarted.Ifnot,theenginemaybecomedamaged.Iftheoillevelisalreadyatthefullmark,thenoilisjustaslikelytobeadequateforthe five hour job as the one hour job. If the oil level is full, there will be a lubricating film on all the moving parts. Likeoilforanengine,phosphorusandpotassiumneedsforagrowingseasonarenotdependentonhowmuchistobegrown,butratheronwhethertheinitialconcentra-tionofphosphorusattheroot-soilinterfaceisadequate.

(usually on the lower part of the plant) up the plant to newly developing tissue. When the old tissue becomesdeficient, characteristic symptoms usually appear.

Phosphorus deficiency usually is characterized by a purplecoloringofthestemorstalknearthegroundleveltogether with a purple and/or yellow coloring of thelowerleaves.Someplantshaveanormalpurplecoloringof the base of the stalk so this symptom is not alwaysreliable.

Potassium deficiency shows up as a chlorosis or yel-lowingofthetipsoftheoldleavesthenprogressestowardthebaseoftheleafalongthemargins.Withinafewdaysthe chlorosis develops into brown, dead tissue (necrosis) along the leaf margins (sometimes referred to as firing of the older leaves) (Figure 4.8). Dead tissue along the leaf margins can also result from excessive water stress ordroughtyconditions.

Adequacyofphosphorusandpotassium in the soilforplantgrowth isdeterminedbyacalibratedsoil test,a concept that is not easy to understand. However, theuse of a soil test is similar to the use of the dip stick,commonly provided to check the oil level of internalcombustionengines.Whentheenginewasdesigned,anengineeraddedtherightamountofoiltothecrankcase(or oil reservoir) for the oil pump to be able to pump it toall themovingparts.Then,with theenginestopped,theengineerinsertedarodthroughaholeintheengineblock,intothecrankcaseandtheoilitheld.Therodwasremoved, the oil level noted, and a line with the wordfull stamped at that point on the rod. This identified the criticallevelfortheengineoilsupply.Nexttheengineerdrainedaquartofoil fromtheengine, inserted therodagain,notedtheoillevelontherodandstamped1quartatthatpoint.Thisresultedincalibratingthedipstick.

Nowwheneverthedipstickisremoveditwillindi-catewheretheoillevelis,comparedtowhereitshouldbe,andifitisnotfullyouwillhavesomeideaofhowmuchtoadd.Ifthelevelisjust1/4inchfromthefullmarkyouwillprobablynotdoanythingaboutit.Butifitisalmostaquart lowandyouaregettinggasataservicestationanyway,youwillprobablyaddenoughoiltobringittothefullmark.Goodsoiltestsarecalibrated,asisOSU’ssoiltest,toidentifytheneedforphosphorusandpotas-sium fertilizer as shown in Table 4.1 (page 18).

Unlikeengines,whichmaybeharmedifafullquartofoilisaddedwhenonlyhalfaquartisneeded,addingan extra 1/2 lb of P2O5 or K2O will not hurt the soil orplants.However,largeexcessesmaybeharmfultoplantsandcouldcontributetolocalstreamorpondpollutionifheavyrainscausesurfacerunoffandsoilerosioncarryingnutrientstobodiesofwater.

Phosphorus and PotassiumDeficiency Symptoms

Like nitrogen, phosphorus and potassium are each

translocated inplantsalthough theyareconsideredrel-atively immobile in soils. When the root system is notfurnishingnewvegetativegrowthanadequatesupplyofthesenutrients,thenutrientsaremovedoutofoldtissue

17

Figure 4.8. Notice the slightly discolored areas in the growth of these vegetable plants. This is due to a mild deficiency in nutrients.

18

Table 4.1. Amount of phosphorus and potassium fertilizers needed based on soil test calibrations for home landscapes.

Soil Test P Index Fertilizer P2O5 Required

-----lbs/1000 sq ft-----

0 to 20 2.5

21 to 40 2

41 to 65 1

>65 0

Soil Test K Index Fertilizer K2O Required

-----lbs/1000 sq ft-----

0 to 100 6

100 to 200 3

200 to 300 1

>300 0

Organic Gardening and Nitrogen

Nature’s Conservation of NutrientsWhen plants die and the residue is in contact with

soil, a decay process carried out by soil microorgan-ismsgraduallyconvertstheplantresiduetosoilhumus,or what is commonly called soil organic matter. Theresidue is decayed because the microorganisms get theenergyandcarbontheyneedfromtheresidue.Becausethe microorganisms are micro plants, they need all theessential chemical elements already identified for plants inthelandscape.Theygetthesenutrientsfromtheplantresidueastheydecayit.

Eventually the residue isdepletedasa foodsource,andmanyofthemicroorganismsthemselvesdieandaredecayedbythosefewremaining.Whentheenvironmentfordecayisaerobicmuchofthecarbonintheresidueisconvertedtocarbondioxidegasandlosttotheatmosphere.Asaresult,theothermineralnutrientsbecomemoreandmoreconcentratedwithtime.Hence,humusiscommonlyanutrientrichcomponentofthesoil.Itisnature’sstore-houseforrecyclednutrientsthatcanbeslowlyreleasedtosupportcontinuedgrowthofhigherplants.

Soils that are naturally high in organic matter, andhavenotbeenfarmed,areusuallyfertile,thatistheyhaveagoodsupplyoftheessentialnutrientelementsforsup-portingthegrowthofhigherplants.However,soilsthatarenearlydevoidoforganicmatterarenotnecessarilyinfer-tile.Agoodexampleoffertilesoils,lowinorganicmatter,arethedesertsoilsofthesouthwestU.S.Whenirrigatedand properly fertilized these soils are very productive(e.g., the San Joaquin Valley in Southern California).

The Nitrogen Cycle

Themost importantof thenaturally recyclednutri-entsinthelandscape,especiallyinthegardenandlawn,is nitrogen. Nitrogen is most important because it isusually ingreatestdemandbygrowingplantsandalsopresentinhighconcentrationinplantresidue.Thiswillbemoreobviousasweconsiderthedynamicsofnitrogenrecycling (Figure 5.1).

Humus to Fertilizer Nitrogen

When plant residues decay, some of the residuebecomeshumus-likeandaddstothesoilorganicmatteralreadypresent.Also,asshowninFigure5.1,someoftheNintheplantresiduemaybereleasedinthedecayprocessand be present as ammonium nitrogen (NH4-N). When the soil is well aerated, the ammonium nitrogen is con-

Chapter 5Managing Nitrogen

Figure 5.1. Natural biological cycling of nitrogen from organic to inorganic (mineral) forms and its use by growing plants.

NitrateNitrogen

AmmoniumNitrogen

Plant Residue

Residue Decay

Soil OrganicMatter (humus)

vertedtonitratenitrogen(NO3-N). The steps that convert nitrogenfromtheplantresiduetonitratenitrogenthatismobileinthesoilareallcarriedoutbymicroorganismsinthesoil.Infact,nitrogenthatispresentinhumuscanalsobeconvertedtonitratenitrogenbythesamemicroorgan-isms.Thenitrogenreleasedfromtheseorganicmaterialsisthesameasthenitrogensoldasfertilizers,likeammo-nium nitrate. Plants cannot tell the difference betweenammoniumandnitrate thatwasreleased fromdecayofplantresidueorhumus,andtheammoniumandnitratethatcomesfromuseofammoniumnitratefertilizer.Thechemicalformsofnitrogenareexactlythesame.

Fertilizer Nitrogen to Humus

Iftheplantresiduebeingdecayedispoorinnitrogen,likewheatstraw, then insteadofnitrogenrelease, therewillbenitrogen tie-upasdecayproceeds.Themicroor-ganisms may get enough energy and carbon from thewheatstraw,butnotenoughnitrogen.Inorderforthemto remain active they must get ammonium or nitratenitrogenfromsomewhere,sotheywillusewhatevermin-eral nitrogen is available in the soil (Figure 5.2).

If you are trying to grow vegetables, at the sametime the wheat straw is decaying, the vegetables maybecome nitrogen deficient. This happens because the microorganismsaresoplentifulinthesoil(overamillionper tablespoon of soil) that they will get to the available ammonium and nitrate nitrogen before the vegetableshave their chance. Soil microbiologists like to say “it’slike a banquet, and soil microorganisms sit at the headtable, they get served first.” Figure 5.2 illustrates how soil microorganisms decaying residue low in nitrogen cancauseavailablenitrogentie-up.

19

Organic Gardeners Take Note

ThebasicNcyclespresentedinFigures5.1and5.2arealwayspresent inthesoil.Withoneexception,nitrogencyclingisstimulatedbythesameconditionsthatstimu-late growth of higher plants, like vegetables or flowers. Thisexceptionisthesupplyofoxygeninthesoil.Cultiva-tionbringsair,andoxygen,intothesoil.Eachcultivationstimulates the activity of the nitrogen cycle. Wheneverthe soil is cultivated by hoeing, tilling, or any mixingaction,itwillbeeitheraninitialreleaseortie-upofavail-ablenitrogen.Theresultdependsonwhethertheorganicmatter being decayed is protein rich (release of nitrogen) or protein poor (tie-up of nitrogen), and how much of it ispresent.

A few years ago, a Master Gardener questioned the soil test results for the sample submitted from their rose garden as a part of the Oklahoma County Master Gardener Training Program. The soil test results showed 320 lbs/acre of available nitrate nitrogen. The gardener could not understand why the nitrate level was so high because fertilizer had never been added to the flower bed. When questioned about how the flower bed was managed, the gardener explained “all we ever add is good alfalfa hay as a mulch”.

As demonstrated by the above incident, decay ofprotein rich plant residue, such as from legumes, in asoil-plantsituationwheretheplantsdonotrequiremuchnitrogen,canleadtobuildupofhighlevelsofnitrateinthesoil.Alittlebitofalfalfawillgoalongwayforpro-vidingthenitrogenneededbyroses.Theexcessnitrogenlikely fedbermudagrassandotherresponsiveweeds inthe flower bed.

Organicgardenersmustpayparticularlycloseatten-tiontothekindsandamountsoforganicmaterialaddedto the garden and how often they cultivate. Organic

matteristhemainfoodforthesoilmicroorganisms.Ifthesoilispoorinorganicmatterandplantresiduethenverylittlehappenstonitrogennomatterhowmuchthesoiliscultivated.Thiswouldbetypicalofvirginsoilsinthearidandsemi-aridsouthwestU.S.Ontheotherhand,if it isyourgoaltoincreasethesoilorganicmatterlevelfrom1%to5%thenitwillbeimportanttoaddavarietyoforganicmaterials over a period of several years (at least five). Goodsourcesoforganicmaterialforthegardenincludelawn clippings, tree leaves, animal manure, shreddedpaper, table scraps, hay, straw, cotton seed hulls, pro-cessed sewage sludge, pecan hulls, and most anythingthatisorganic(youcanavoidatrashylookinggardenbycomposting these and taking the compost to the garden). Manydifferenttypesofcompostersareavailable(Figure5.3), and you can choose one to fit your needs.

Fertilizer Nitrogen

NitrateNitrogen

AmmoniumNitrogen

Nitrogen PoorPlant Residue

Residue DecaySoil Organic

Matter (humus)

Figure 5.2. Natural biological cycling of nitrogen from inorganic (mineral) forms to organic nitrogen.

Figure 5.3. Mini-composters can be used in the yard to convert organic waste into fertilizer.

By adding small amounts of different compostingmaterials, severe nitrogen tie-up or release is avoided.Forexample,whenbothstrawandalfalfahayareaddedtherapidreleaseofnitrogenfromdecayingalfalfaiscom-pensatedforbytherapidtie-upofnitrogenbydecayingstraw.

A county agricultural educator called a few years ago, wanting assistance with a new homeowner who was having difficulty establishing a bermudagrass lawn in southern Oklahoma. The previous owners of the house had raised rabbits (they were not gardeners), and in preparing to move after selling the house, they cleaned all the rabbit hutches and left the remains on the area the new owners wished to convert to a lawn. The new owners simply tilled the area and sprigged bermudagrass. After the bermudagrass failed to grow and spread, the new owners took a soil sample from the area and submitted it for a routine test. The results showed a nitrate nitrogen level of over 1000 lbs/acre (about 20 times higher than desired). The bermudag-rass was failing because of excess nitrogen causing a salty condition (tying up water). The question was “how do we get rid of the excess nitrate nitrogen?”

20

There were several possible solutions to the problem, but the easiest, least expensive, and most conserving was to take advantage of nature and the nitrogen cycle illustrated in Figure 5.2. The homeowner was advised to till as much wheat straw into the soil as possible. This allowed the soil microorganisms to use up the excess nitrate nitrogen as they decayed the nitrogen-poor straw. It converted all the readily available nitrogen (nitrate) into a slow release form (microorganism bio-mass and humus). In a few weeks the bermudagrass flourished.

Instant Organic Gardening

Thereisanexceptiontotheruleofaddingmoderateamountsofavarietyoforganicsourcestothegardenovera five year period to raise organic levels to 4% or 5%. An exceptionwouldbetheadditionoforganicmaterialthatisnativeornaturaltosoil,thatishumusorpeat.Peatorcompostedplantresiduehasalreadyundergonetheinitialrapiddecayresponsibleforreleaseortie-upofnitrogen.

Normaltillagedepth,anddepthofthegreatestrootmassformostplants,isabout6inches.Theweightofsoilina10ftx10ftarea,6inchesdeepisabout4,000lbs.Itwouldtakeabout160lbsofpeat,addedtothisarea,toincreasethesoilorganicmatterfrom1%to5%,onaweightbasis.Ifaddedinasingleincorporation,thiswouldincreasethesoil-peat volume about 20% (soil surface would raise atleast 1 inch). A more uniform mixture will be obtained by splittingtheadditionintotwoapplicationsaboutamonthapart.Limitusingcompostoranimalmanuretonomorethanhalfaninchthickperapplication.Otherwise,plantsmaybeaffectedbytoomuchsaltornutrientsadded.

Soil Organic Matter Maintenance

Oncesoilorganicmatterlevelshavebeenbuiltupto4%or5%,theywillonlyremainatthatlevelifabalanceis maintained between cultivation, which destroys soil

organicmatter,andadditionofplantandanimalresidue,which builds soil organic matter.An important naturalinputistogrowhighyieldsfromplantsthatarespacedclose together (Figure 5.4). Avoid having bare ground in thegarden.Themoreyoucanusethesoiltogrowplants,thericheritwillbecomeinorganicmatterandhumus.

Cultivate only when it is necessary. For small non-commercial gardens, it may be possible to eliminatecultivationaltogetheroratleastreduceittoonlyoneortwocultivationsperyear.

21

Figure 5.4. Note the spacing between the plants in this vegetable garden.

Thethreemainreasonsforcultivatingaretocontrolweeds, incorporate plant residue, and prepare a seedbed.Weedscanbepulledbyhand,plantresiduecanbeshreddedandleftasamulchonthesurface,andonlyanarrowbandofsoilneedstobedisturbedtopreparesoilforplantingarowofvegetables.Thegardenareathatisnotcultivatedwilllooktrashy,butitcanbeveryproduc-tive and will be easier to maintain soil organic matterin than the area that is cultivated. One timely cultiva-tionayearcanaccomplishall threeof theobjectivesofcultivating.

22

Nonsynthetic Fertilizers

Complete Fertilizers

Thetermcomplete,whenusedtodescribefertilizers,usuallyreferstothosematerialsthatcontaineachofthethree major nutrients supplied from the soil: nitrogen,phosphorus, and potassium (commercial sources usu-ally identify the nutrient concentrations in this sameorder,aspercentageofN,P2O5,andK2O). However, there are situations when the homeowner is interested in anutrientsupplementthatiscompleteinthesensethatitalsocontainsthesecondaryandmicronutrients.Themostcommon situation is for house plants and other plant-ingsthataregrowninasoil-lessmedium,suchasplantspottedinvermiculite.

The term nonsynthetic is used instead of naturalbecausesomeofthecommerciallyavailablefertilizersaremorenaturalthansomeoftheso-callednaturalproducts.Thisisbecausewithoutmuchprocessingtheyareusedastheyarefoundinnature.Anexampleofthisisthecom-mercial fertilizer potassium chloride. It is mined fromnearlypuregeologicaldepositsandexceptforcrushingandscreeningismarketedasis.Bonemeal,ontheotherhand,isextensivelygroundtoapowderbeforeitismar-keted as a natural material. Similarly, blood meal mustreceiveconsiderableprocessingbeforeitcanbemarketedasanaturalmaterial.

Compost

Sinceplantsmustcontainalltheessentialplantfoodelementsiftheyaretocompletetheirlifecycle,itstandsto reason that these nutrients should all be present indecayedplantmaterial,suchashumusandcompost.Forthisreason,compostisagoodsourceofallnutrients,anditprovidestheminaboutthesameproportionasneededbytheplantsyouaregrowing(somenutrientscanbepar-tially lostasagasorwashedoutof the residueas it isdecaying or being stored).

Adding a small amount of compost to the growthmediaforpottedindoorplantsassurestheywillnotsufferdeficiencies of the micronutrients. Maintaining a high level ofsoilorganicmatterinthegardenwillalsoassureanabun-dant supply of micronutrients (Figure 6.1). An additional characteristic of organic sources of the nutrients is thattheyareslowrelease,thatis,theybecomeavailablegradu-ally over time as the organic matter continues to decay.This is usually a benefit, but can be a disadvantage when you wish to correct an existing nutrient deficiency quickly. Slowreleasenutrientsourcesmaybeinadequatetosatisfythenutrientdemandsofrapidlygrowingplants.

Chapter 6Nutrient Supplements for the Soil

Table 6.1. Approximate nutrient content of selected nonsynthetic fertilizer materials.

Material Nitrogen (N) Phosphorus (P2O5) Potassium (K2O)

-------------------------- % --------------------------

Bone meal 3 22 0

Cottonseed meal 6 3 1.5

Soybean meal 7 1.2 1.5

Animal manure (dry) 2 2 2

Alfalfa hay 2.5 0.5 2.5

Wheat straw 0.5 0.15 0.1

23

Figure 6.1. An example of a composting unit for use in the home garden.

Incomplete Fertilizers

Other fertilizers that have not been synthesized, ormanufactured, and are marketed as primary source ofonlyoneortwonutrientsarelistedinTable6.1.

Nonsynthetic fertilizers are characteristically slow-release and have low concentrations of the nutrientscontained. Consequently, if the soil is inherently deficient inoneormoreofthenutrients,largequantitiesofthefer-tilizerwillneedtobeaddedto thesoil.Forexample, ifyouwish toadd1 lbofnitrogen in the formofanimalmanure,itwillbenecessarytoaddabout50lbsofcom-posted manure (50 x 0.02 = 1.0). However, since only about halfofthenitrogeninthemanurewillbecomeavailablein the first year, it will be necessary to double the addition andadd100lbs.

Synthetic Fertilizers

Complete Fertilizers

Oneofthemostcommoncompletefertilizersusedbyhomeownershastheanalysis10-20-10,andiscommonlyreferredtosimplyas,ten-twenty-ten.Thisfertilizercon-tains10%watersolublenitrogen,20%availablephosphate(expressed in units of P2O5), and 10% available potash (expressedinunitsofK2O). Nurseries and garden centers usuallymarketthisfertilizerin40lbbags.Thisfertilizerispopularbecauseithasrelativelylownitrogencontentandhighphosphatecontent.Mosthomeowners thinkaboutfertilizing their gardens and lawn in the spring, whenthesoiliscoolorevencold.Phosphateuptakebyplantsisslowincoldsoilandsoadditionofafertilizerwitharelativelyhighcontentofphosphateoftenwillstimulateearlygrowthofgardenandlawnplants,ifavailablesoilphosphorus is not adequate. The low nitrogen contentwillallowthehomeownertousethewholebag(aswillsurely happen) without applying excessive nitrogen and causingexcessivegrowth.Ifthe40lbbagisevenlyspreadover4,000sqftoflawnandgardenthentheapplicationrateofnitrogenwillbe1lbofnitrogenper1000sqft.Thisrateisagoodstartinglevelformostplant-growthsitua-tions.Evenifthehomeownerhasonly2000sqftofareatofertilize,theratewillonlybe2lbsofnitrogenper1000sqft.Thisisusuallynotenoughtocauseexcessivegrowthduring cool spring weather. A final reason for 10-20-10 beingsuchapopularfertilizeristhatbecauseofthelowanalysis,theusercanspreaditatahighenoughrate(10lb of material per 1000 sq ft) that it is easy to see where youhavebeenandfeelasenseofaccomplishmentwhenthe jobiscompleted,withoutcausinganyharm(Figure6.2).

Therearemanyothercompletefertilizers,suchas19-19-19,10-10-10,12-24-12,6-24-24,29-3-4,etc.Thesehavebeenmanufactured toprovideamoreconcentratedfer-tilizer to meet the needs of different plants in differentlocations.However,thereislittlemeritforthesedifferentfertilizermaterialssincesoilsvarygreatlyintheircapacitytosupplyeachofthenutrientsandbecauseoncethefer-tilizerhasbeenapplied,itsreactionwiththesoilchangestheratioinwhichthenutrientsaresuppliedtoplants.

Single and Double Nutrient Fertilizers

Nitrogen

Themostcommonsyntheticfertilizersforsupplyingonlynitrogenandtheconcentrationofavailablenitrogenineacharelistedbelow:

1. Ammonium sulfate (21% N)2. Ammonium nitrate (34% N)3. Urea (46% N)

Theseareallexcellentsourcesofnitrogen.Ammoniumsulfateisthemostacidformingandmay

be preferred for calcareous or high pH soils. Althoughit also provides sulfur, this is seldom a benefit because sulfurisusuallyadequate.

Ammoniumnitratemayresultinslightlyfasterplantresponsebecausesomeof thenitrogen isalready in themobile,nitrateform.Thismaybeimportantwhentryingtoimprovethenitrogensupplytoplantsgrowingincold,wet soils (early spring). Because of its use in the 1995 Okla-homaCitybombing,availabilityhasdecreased.Althoughithasbeenusedasaningredientforexplosives,ammo-nium nitrate fertilizer is a safe product (special effortmustbetaken,asinthecaseoftheOklahomabombing,to cause it to explode).

Urea is the highest analysis dry nitrogen fertilizeravailable and, consequently, it is the cheapest on a perpoundnitrogenprovidedcomparison.Adisadvantageofureaisthatitmustreactwiththeenzymeurease,present

24

Figure 6.2. The consistent color in this lawn indi-cates a properly applied fertilizer.

25

inallsoilandplantmaterial,toconvertittoplantavail-able ammonium. This requirement may delay plantresponse (one week compared to ammonium nitrate) and presentsanopportunityforlossofnitrogenbyvolatiliza-tionasammonia(agas,likethatinammoniatedcleaningsolutions). The risk of this happening is increased if the ureaisappliedtowetturfandallowedtoreactforseveralhourswhiletheleafsurfacesarewetandthenwarm,dry,windyconditionscausetheturftodry.Thistypeoflosscanbeeliminated,orminimized,iftheareaisirrigatedorcultivatedsoonafterfertilizing.

Phosphorus

Theonlycommonfertilizerthatsuppliesonlyphos-phorusiscalledtriplesuperphosphate.Ithastheanalysisof 0-46-0 (46% available phosphate) and is made up of thecompoundmonocalciumphosphate.Sincethebiggestfertilizermarket is commercial agriculture, and ithasahigher demand for nitrogen than phosphate, the fertil-izer industry manufactures much more diammoniumphosphate (18-46-0) and it is often more readily available, andatalowercostperpoundofphosphate,than0-46-0.Eitherofthesewillbeexcellentsourcesofphosphateforthelawnorgarden.

Potassium

Themostcommonfertilizerthatsuppliesonlypotas-sium,orpotashasitissometimescalled,isthematerialcalledmuriateofpotashorpotassiumchloride.Thisfer-tilizerhastheanalysisof0-0-60andisagoodsourceofexternal potassium. It is a natural material mined fromgeological deposits and may be either pink or whitegranules.

Handling Fertilizers

Whentheyreactwithwater,syntheticfertilizerswilloftenbecomecorrosivetometalsandnonsyntheticmate-rials will usually begin biological reactions resulting inrot. It is agoodpractice to thoroughlywashcontainersandapplicatorsafterfertilizing,andtostoreunusedmate-rialinacooldryplace.Wheneverfertilizermaterialsarelabeled,carefullyfollowinstructionsforuse.Somefertil-izersshouldnotbemixedwithotherstopreventcakinguporotherpotentialproblems.

26

When and How Often to Soil Test

Soil Testing RationalSoil testing should be viewed with

the same approach as one would taketowardservicingthelawnmowerorcarengine. If we do not know how muchgas and oil are present, we check thefuel gauge and dip stick. In Chapter 4,nitrogenneedswererelatedtogasforanengine and phosphorus and potassiumneedswerecomparedtoengineoil.

Plant available nitrogen in the soilchanges considerably fromyear toyearandevenwithinaseason.Plantgrowth,additionoffertilizernitrogen,anddecayof organic mater, all will cause signifi-cant changes in available nitrogen injustafewdays.Itisnotnecessarytosoiltest each year or within the season tocloselymonitornitrogenneeds.Instead,add small amounts of fertilizer nitrogen (or aerate thesoilbyshallowcultivationtopromotereleaseoforganicnitrogen) to improve plant growth or green color.

ThevalueofsoiltestingisinidentifyingwhetherornotsoilpH,availablephosphorus,andavailablepotassiumexistatdesirablelevels,andthenchangingmanagementofthetestedareaaccordingly.Sincethesesoilpropertiesdonotchangemuchfromoneyeartothenext, it isnotnecessarytosoiltestthesameareaeachyear.However,asoiltestonceeverythreeyearswillprovideinformationneededtomanagethelawnandgardenproperly.

How to Collect a Representative Soil Sample

Homeowners and lawn care professionals mustrealize the spatial variability existing around the yardwhen collecting a soil sample. Each sample collectedshouldrepresenttheareatobefertilized.Thefertilitylevelin the vegetable garden may be different from that of aflower bed. Soil test parameters in the front yard may be drasticallydifferentfromthoseinthebackyard.Therefore,separate samples may need to be collected from thoseareassothattheycanbetreateddifferentlyasshowninFigure7.1.Avoidsamplingodd-ballareas.Acoreorslicefromthesurface toadepthof6 inchesshouldbe takenfrom15to20locationsineachareaandcombinedintoonerepresentative sample to be tested (Figure 7.2).

Chapter 7Using Soil Testing to Guide

Nutrient Management

Figure 7.2. Key points of taking a good soil sample.

27

Get a Useful Sample

15-20 coresSoil probe

Right Depth(plow layer or 6 inches)

Clean bucket

Figure 7.1. Taking soil samples separately to accurately represent pH and soil fertility levels of the vegetable garden, flower bed, and lawn.

AzaleasSample 4

Vegetable GardenSample 3

Back lawnSample 2

Healthy Lawn

Each soil sample should represent only one soil condition

Front LawnSample 1

Yellow or Bare Spots

X

XX

X

X

X

X XX

XX

X

XX

X

X

X

XX

X

X

X X

X

X

X XXXX

XX

XX

X

SoilsamplesmaybesubmittedtoyourcountyOSUExtension office. They will send the samples to the Soil, Water,andForageAnalyticalLaboratoryfortesting,andthensend the resultsback toyouwith fertilizer recom-mendations. Soil samples are analyzed routinely forpH,nitratenitrogen,phosphorus,andpotassium,whilesecondary and micronutrients are tested on request. Anumberofothertestssuchassoilorganicmattercontentarealsoavailablethroughthelab.

Soil Test Interpretations

Table7.1 lists thesoil test results receivedbymem-bersofarecentMasterGardenersprogramthatinvolvedsamplesfromtheirlawnsorgardensbeingtestedbytheOSUSoilTestLab.

Thehighestandlowestvaluesforeachpartofthesoiltest have been highlighted to call attention to the widerangeinresultsofsamplesthatcamefromasmallurbancommunity.

Soil pH and BI (buffer index)

The lowest pH was 4.7. This identifies a soil that is acidic enough to prevent normal growth of bermudag-rassturfandmostgardenplants.Thisacidicsoilwouldbeidealforblueberriesandazaleas,alsofescueturfwoulddowellatthispH.ForthenormalgrowthofotherplantsahigherpHisdesirable,andthesoilshouldbelimedforthatpurpose.

Ifthedecisiontolimethesoilismade,thentheamountoflimetoapplycanbeestimatedfromtheBIvalueinTable2.1.SincetheBIvalue is6.8,accordingtoTable2.1, lime

shouldbeappliedatarateofabout55lbs/1000sqft.Forgardensthe limeshouldbeappliedandincorporatedbycultivation.Thismaybedoneasapartofaregularlysched-uledcultivationtoincorporateplantresidue.Ifthesoilisfromalawnarea,aeratingthelawnafterapplyingthelimewill help get it incorporated. Bermudagrass lawns willbenefit from lime even if it cannot be incorporated when thesoilpHislessthan5.0.Irrigationandrainfallwillhelpmovethelimedownintothethatchlayer,andwithtimemovementintocracksandwormchannelswillbringitintocontactwiththeacidsoilneartherootswhereneutralizewilloccur.

Once the liming has been done, it may take a fewmonthsbeforethepHchanges,butitshouldnotbeneces-sarytolimeagainforseveralyears.SomeofthesoiltestsreportedinTable7.1showBIvaluesof7.1orabove.NotefromTable2.1thattheseonlyneedabout23lbs/1000sqft,ifthedecisionismadetoraisethesoilpHfromtheexistingleveltoapHnear7.ItisinterestingtonotethatthepHofsample6ishigherthanthatforsample7,butsample6hasa lowerBIvalueandrequiresmorelimetoraisethesoilpH.Thisisaresultofsample6containingmoreclayandorganicmatter,thusithasahigherbufferingcapacitythansample7.

Table 7.1. Typical lawn and garden soil test results.

NO3-N P K Sample No. pH BI lb/acre -----lbs/ac or (2 x ppm)-----

1 6.5 20 780 640 2 6.3 7.1 19 640 710 3 6.1 7.3 26 175 783 4 5.5 7.1 18 216 1052 5 6.5 6 149 347 6 4.8 6.6 8 247 266 7 4.7 6.8 5 152 466 8 6.7 9 392 569 9 6.4 7.3 7 235 584 10 5.6 6.9 10 560 504 11 6.2 7.3 14 139 429 12 5.7 7.1 2 264 320 13 6.0 7.2 7 206 435 14 6.5 5 117 367 15 6.4 7.3 3 148 197 16 6.5 16 364 778 17 6.6 12 365 863 18 6.1 7.2 15 294 379 19 6.2 7.2 11 176 579 20 5.5 6.7 15 241 554 21 6.1 7.2 9 122 616 22 5.7 6.9 12 248 479 23 5.7 7.2 18 115 457 24 5.4 6.9 13 197 703 25 6.9 4 203 537 26 7.4 22 244 1157 27 6.0 7.1 37 153 787 28 6.6 2 19 401 29 6.7 30 570 810 30 6.5 95 1330 653

28

Available Nitrate Nitrogen (NO3-N)

Availablenitrogenvaluesrangedfromalowof2lbs/acretoahighof95lbs/acre,withmanyofthesoilscon-taininglessthan20lbsnitrogen/acre.Howthesevaluesareinterpreteddependsuponwhattimeofyearitisandalso what is being grown (or planned) at the time.

Thesoiltestreportsavailablenitrogeninunitsoflbs/acre,theapproximateequivalentinlb/1000sqftiseasilyobtained by dividing lb/acre by 44 (because an acre is43,560 sq ft). Thus, the soil test reporting 95 lb nitrogen/acreisaboutthesameas2lbofnitrogen/1000sqft.Agoodstartingpointatthebeginningofthegrowingseason,foranycrop,is40lbsnitrogen/acreorabout1lb/1000sqft.Valueshalfthisamountortwicethisamountarenotnec-essarilyaproblem,buttheywillneeddifferentdegreesofattentionduringthegrowingseason.

For example, if the sample was taken in the springfromeitherabermudagrass lawnoragarden, then thetestvalueof95 indicatesagoodsupplyofnitrogen forallthespringgardencropsthroughmaturity,andenoughnitrogenforthelawnintoJuly.Thesoiltestvalueof2foravailablenitrogenmaybe interpretedthesameaszero,and in thespringof theyear, this low levelofnitrogen(as well as any value below 20 lb/acre) is an indication plantgrowthwillbelimitedwithoutadditionofsupple-mentalnitrogen. If thesoil ishigh inorganicmatter,orhasrecentlyreceivedanadditionofnitrogenrichorganicmatter,cultivationwillaeratethesoilandstimulatereleaseofavailablenitrogenfromtheorganicmatter.Otherwise,nitrogen fertilizer should be added at a rate to provideabout1/2lbofnitrogenper1000sqft.

Having to add fertilizer to provide more nitrogenbrings up the question of how much fertilizer must beaddedtogetthepredeterminednitrogen.Theanswertothisproblemdependsuponthefertilizerbeingused,sincecommercialmaterialscontainingjustnitrogenwillrangefrom 46% (urea) to 21% (ammonium sulfate). Once we havedecidedonhowmuchnitrogentoadd,theamountoffertilizermaterialrequiredtogetthatmuchnitrogeniscalculatedbydividing thenitrogenamountby theper-centNinthefertilizerandmultiplyingtheanswerby100.Forexample,ifweneed1lbofNfromammoniumnitratefertilizer (34% N), the amount of fertilizer needed is

(1 lb N/34) x 100 = 2.94lbsammoniumnitratefertilizer

Mostof thesoil test results listed inTable7.1showavailablenitrogenbelow40 lbs/acreor1 lb/1000 sq ft.Forsamples thatmayhavebeentaken in the fall, theselevelsrepresentgoodnitrogenmanagementbecausetherewillbeverylittleavailablenitrogeninthesoilduringthewinterwhennocropsorplantswillbegrowing.Justaswewouldliketohavethefueltankemptyforthelawnmower when it is put away for the winter, there is noadvantageinhavingalotofavailableNinthesoilduringthetimeofyearwhenwewillnotbegrowinganything.

ThedisadvantageofhavinghighlevelsofavailableN in thesoil late in the fall, forexample the95 lb/acreforsample30inTable7.1,isthatitwillstimulategrowth

of weeds that are winter annuals, like henbit. To avoidthis, it is best not to fertilize after the first of September andallowthelawnandgardenplantstodepletethesoilof available nitrogen (the exception would be for falland winter plantings, like fescue lawn). Too much late nitrogenmayalsopromotediseasessuchasspringdeadspotsandreducethewinterhardinessperennialplants.

Soil Test Phosphorus (P)

The30lawnandgardensampletestresultsforphos-phorusreportedinTable7.1rangedfrom19to1330.Thecalibration for phosphorus in Table 4.1 shows that thevalueof19indicatesaphosphateneedofabout2to2½lb/1000sqft.Thiscouldbemetbyapplyingabout10lbof10-20-10per1000sqftofarea (2 lbP2O5/20) x 100 = 10lbfertilizer.Becausephosphatedoesnotmoveeasilyinthesoil,thebestresponsetofertilizerphosphatewillbeobtainedwhenitcanbemixedwiththesoilbyalightcultivation.Thisistrueevenifthefertilizerisaliquidfor-mulation,because chemical reactionsat the soil surfacewillpreventitfrommovingmorethan1/2to1inchdeepin the soil.Also, since it requires about 15 lbs of fertil-izerphosphatetoraisethesoiltestvalueoneunit(from19 up to 20), it will take several annual applications of phosphatetogetthesoiltesthighenoughtoeliminatetheneedforphosphatefertilizeradditions.

Just as it will take many years of small phosphateadditions to raise the soil test level to adequate, it willtake many years of crop removal to lower the soil testfrom high values to values below 65 that would signalthe need to add phosphate. Except for the single valueof19,soil testphosphorus levels inTable7.1allexceed100, with many in the 200 and 300 range. These highlevelsindicatethesoilwillbeabletosupplyplantswithadequatephosphateformanyyearswithoutfertilizerorcompostadditions.

Forlawnswherethesoiltestphosphoruslevelis100ormoreandtheclippingsarenotremoved,therecyclingofsoilandplantphosphatewillmaintainhighavailablesoilphosphatelevelsforatleast10to20years.Wheresoiltestphosphorus levelsare500and600, there isenoughphosphorusinthesoilfortwotothreegenerations.And,fortheareathathasasoiltestlevelof1330,thesoilcouldbebaggedandsoldforfertilizer,oratleastexcellentpot-tingsoil.

Knowingly building soil phosphorus to such highvaluesisfoolish.Unknowinglydoingitisamarkofigno-ranceordisregardfortheenvironmentorboth.Tohaveanareawithaphosphorussoiltestof500,600orashighas1330,islikehavingapickuptruckwithanenginethatdoesnotuseoil, the crankcase is full, and theoperatorhas four 55-gallon barrels full of oil in the back, just incase. The soil tests listed in Table 7.1 were from northcentral Oklahoma (Enid) but, are typical of gardeners as illustrated inFigure7.3 for samples fromanOklahomaCitygroupofgardeners.Oftheover100samplestested,about 90% were adequate (soil test P of 65 or higher) to veryhighinavailablephosphorus,withabout30%aboveasoiltestlevelof500.

29

Soil Test Potassium (K)Soil testpotassiumvaluesshownforEnidareagar-

dens and lawns (Table 7.1) are generally adequate and typical of soils in central and western Oklahoma. OnereasonforthisisbecausethesesoilsdevelopedunderlowrainfallandareinherentlyrichinK.ThesecondreasonisthatthemostcommonlyusedfertilizersarelowintheirsupplyofKcomparedtoP.Thus,withcontinuedannualapplicationsof10-20-10fertilizer,phosphorusbuildsupinthesoilfasterthanpotassiumbecausetwiceasmuchisadded.Likephosphorus,unlessmostofthevegetativematerialgrowneachyearisremovedfromtheareaandnotrecycled,existingadequatesoilsuppliesofKwillper-sistformanyyears.

Table 4.1 identifies 300 as the soil test level above whichpotassiumisadequate.Onlytwoofthe30samplesinTable7.1werelessthan300forpotassium.Thelowest,avalueof197,isnotlikelyaproblemformostplantings.To assure potassium will not be deficient, a rate of 1 to 3 lbsK2O/1000sq ftwouldbe recommended.Thiscouldbeachievedbyspreading2to6lbsof0-0-60fertilizerper1000sqft,eachyear.

An alternative to using commercial fertilizer tosupply potassium is to spread fireplace ash on potassium deficient soils. Care must be taken to not exceed rates of 10gallonsofashper1000sqftonsandysoilsand20gal-lonsonloamyorclayeysoils.A10gallonbucketofashwillprovideabout3lbsofpotash(availableK2O). Areas that receive ash should be recorded and not receive asecond application for 10 years. Excessive use of fireplace ash can lead to the development of an alkali soil (highpH and poor water infiltration) as described in Chapter 2.Directcontactoffreshashwithactivelygrowingplantsmayresultininjurysoitmaybesafertoapplyashduringtheoff-season.

General Guidelines of Fertilization

A soil test estimates the ability of soil to providenutrientstoplants.Thisanalysistakessomeoftheguess-workoutoffertilizer.Thekeyforausefulsoiltest istoprovidethelabwithagoodsoilsample.Formosthom-eowners, you may only buy fertilizers formulated forlawnandgardensfromnurseriesordepartmentstores.IfyoursoiltestisshowinglowPandKaswellasN,useacompletefertilizer,suchas19-19-19forayearortwoandthenretestyoursoil. If thetest isalreadyhighinPandK,applyfertilizerscontainingNonlyorlowinPandK,such as: 46-0-0 (urea), 27-3-3, and 31-3-4. This will avoid over applying certain nutrients (Figure 7.4).

Figure 7.3. Soil test phosphorus for Oklahoma County Master Gardeners.

1 11 21 31 41 51 61 71 81 91 101Sample

2500

2000

1500

1000

500

0

So

il Te

st P

hosp

horu

s

30

Figure 7.4. Over fertilization from compost resulted in a huge vine but small tubers for this yam plant that was grown in a raised garden.

Figure 7.6. To protect the environment, the fertilizers and grass clippings should be collected and spread on lawns.

31

Environmental ConsiderationsExcessfertilizerappliedtotheyardorlandscapecan

beapollutionsource.Whenitrains,theextraplantnutri-ents from lawns may be washed through storm drainsto nearby lakes and streams (Figure 7.5). Nutrients that reach lakesandstreamsstartaprocesscalledeutrophi-cation. Rapid growth of aquatic weeds and algae useup the oxygen in the water. Extreme cases can lead todeteriorated water quality and fish kills. It is more envi-ronmentallyfriendlyifamulchinglawnmowerisusedsinceitreturnsgrassclippingstothelawn.Thisrecyclesnutrients,minimizesfertilizerinputs,andcutsdownonthevolumeofsolidwaste.Additionally,allthefertilizersandgrassclippingsonthesidewalkcanbewashedaway;therefore, theyshouldbecollectedandputbackon thelawn or garden (Figure 7.6).

Figure 7.5. Abundant plant growth surrounding a small pond due to excessive nutrients in the water.

32

Chapter 8Reference Tables

Table 8.1. Homeowners Table of Measurements.

Container Fertilizer ---------Weight--------

grams pounds

34.5 oz

Large Coffee Can Ammonium Nitrate (34-0-0) 2635 5.81

Urea (46-0-0) 2236 4.93

Diammonium Phosphate (18-46-0) 2503 5.52

Potassium Chloride (0-0-60) 2993 6.60

13 oz

Coffee Can Ammonium Nitrate (34-0-0) 889 1.96

Urea (46-0-0) 712 1.57

Diammonium Phosphate (18-46-0) 861 1.90

Potassium Chloride (0-0-60) 1011 2.23

1 gallon recyclable plastic milk container

Ammonium Nitrate (34-0-0) 3075 6.78

Urea (46-0-0) 2590 5.71

Diammonium Phosphate (18-46-0) 2980 6.57

Potassium Chloride (0-0-60) 3565 7.86

½ gallon recyclable plastic milk container

Ammonium Nitrate (34-0-0) 1483 3.27

Urea (46-0-0) 1215 2.68

Diammonium Phosphate (18-46-0) 1424 3.14

Potassium Chloride (0-0-60) 1700 3.75

33

Theprevioussevenchaptersdiscussedthebasicsofsoil and nutrient management in the yard, and recom-mended techniques to take care of lawns and gardenswhileminimizingtheimpactofouractivityontheenvi-

ronment. Tables 8.1, 8.2, 8.3, and 8.4 contain helpfulinformation on calculating the amount of fertilizers toapplytoagivenarea.

Table 8.2. Amount of nitrogen fertilizers needed at two different rates.

N Turf Recommendations Yard Size, ft2 Fertilizer Quantity to Apply, lbs

1 lb N/1000 ft2 10000 34-0-0 29.4

1/2 lb N/1000 ft2 10000 34-0-0 14.7

1 lb N/1000 ft2 10000 46-0-0 22

½ lb N/1000 ft2 10000 46-0-0 11

Table 8.3. Fertilizer recommendations for various soil test results.

Soil Test Condition Action

pH above 6.0 no change neededpH below 5.5 add lime

Soil test nitrogen less than 40 lb/acre add 1 lb N/1000 sq ftSoil test nitrogen above 80 lb/acre no fertilizer needed

Soil test phosphorus below 65 lb/acre add P fertilizer Soil test phosphorus above 120 lb/acre no P fertilizer needed

Soil test potassium below 300 lb/acre add K fertilizer Soil test potassium above 400 lb/acre no K fertilizer needed

34

A garden reminds us the

value of intention — plan,

prepare, nurture... A garden

lets us work the soil, teach-

ing us everything is interre-

lated and independent. Why

not enjoy the company.

– Jean Larson

Additional Information

• 18-46-0isnotrecommendedunlessyoursoiltestindicates that you have a P deficiency

• If10-20-10 is the fertilizermaterial,apply twicetheamountindicatedfor18-46-0

• lb/acredividedby40=1lb/1000sqft

35

Table 8.4. Fertilization Tips

Bermudagrass Lawn Nitrogen rate = 1 lb N/1000 sq ft/month

Yard Area, Sq ft 1000 3000 6000

Fertilizer Source 46-0-0 34-0-0 18-46-0 46-0-0 34-0-0 18-46-0 46-0-0 34-0-0 18-46-0

Number Of 13 Oz Coffee Cans Of Fertilizer To Apply 1.4 1.5 2.9 4.2 4.5 8.8 8.3 9.0 17.5

Number Of 1/2 Gallon Milk Containers Of Fertilizer To Apply 0.8 0.9 1.8 2.4 2.7 5.3 4.9 5.4 10.6

Vegetable Garden Nitrogen rate = 1 lb N/1000 sq ft/month

Garden Area, Sq ft 200 600 1000

Fertilizer Source 46-0-0 34-0-0 18-46-0 46-0-0 34-0-0 18-46-0 46-0-0 34-0-0 18-46-0

Number of 13 Oz Coffee Cans of Fertilizer to Apply 0.3 0.3 0.6 0.8 0.9 1.8 1.4 1.5 2.9

Number of 1/2 Gallon Milk Containers of Fertilizer to Apply 0.2 0.2 0.4 0.5 0.5 1.1 0.8 0.9 1.8

1 46-0-0 (Urea)2 34-0-0 (Ammonium Nitrate)3 18-46-0 (Diammonium Phosphate)

36

Notes