Soils, Fertilizers And Plant Nutrition

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Soils, Fertilizers And Plant Nutrition
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Hanlon, Edward A.
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Soils,FertilizersandPlantNutrition1 TheInstituteofFoodandAgriculturalSciencesisanEqualOpportunity/AffirmativeActionEmployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,ornationalorigin. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/JohnT.Woeste,DeanE.A.Hanlon2PLANTESSENTIALELEMENTSSoilisthenaturalmediumforthegrowthofland plantsandisthesourceofmostofthenutrients necessaryforplantgrowthanddevelopment.The sixteenessentialnutrientelementsrequiredbyplants andtheformsinwhichtheyareabsorbedareshown inTable1.Thenutrientsarerequiredinvarying amountsbyplants,asmaybenotedfromthetable. Forconvenience,thenutrientsusedinlargest quantitiesarereferredtoasmacronutrientsandthose usedinsmallestquantitiesasmicronutrients. Althoughthebulk(93-99%)ofplanttissueis comprisedofcarbon,hydrogen,andoxygen,those elementsseldomifeverlimitplantgrowth.Itisthe nutrientelementsobtainedfromthesoilthatusually limitcropdevelopment.Whenthesoildoesnot providesufficientquantitiesofnutrientsforthe plants,fertilizermustbeappliedtothesoiltosatisfy thecropnutrientrequirement.MACRONUTRIENTSFROMSOILS ANDFERTILIZERSImportantpointsconcerningthemacronutrients obtainedfromsoilsandfrequentlysupplementedby fertilizersarediscussedinthissection. Table1. Nutrientelementsessentialforplantgrowth. Essential Element ChemicalSymbol ChemicalForm(s)UsedbyPlants TypicalPercentofPlants' FreshWeight Carbon C CO3 --,HCO3 45 Hydrogen HH+(water) 8 Oxygen O H2O,otheroxides 41 MACRONUTRIENTS Nitrogen N NH4 +,NO3 2.0 Phosphorus PHPO4 --,H2PO4 0.4 Potassium K K+ 1.1 Calcium CaCa++ 0.6 Magnesium Mg Mg++ 0.3 Sulfur SSO3 --,SO4 -0.5 1.ThisdocumentwaspublishedDecember1992asRF-AA003,FloridaCooperativeExtensionService.Formoreinformation,contactyour countyCooperativeExtensionServiceoffice. 2.ExtensionSoilScientist,CooperativeExtensionService,InstituteofFoodandAgriculturalSciences,UniversityofFlorida,Gainesville.

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Soils,FertilizersandPlantNutrition Page2 Essential Element ChemicalSymbol ChemicalForm(s)UsedbyPlants TypicalPercentofPlants' FreshWeight MICRONUTRIENTS Iron Fe Fe++,Fe+++ 0.02 Manganese MnMn++,Mn+++ 0.05 Copper Cu Cu+,Cu++ 0.001 Zinc ZnZn++ 0.01 Molybdenum Mo MoO4 -0.0001 Boron BBO3 --0.005 Chlorine Cl Cl<0.0001NitrogenBiologicalNAgroupofbacteriacalled Rhizobium whichlive inassociationwiththerootsofleguminousplantscan fixatmosphericnitrogenforthehostplant.Thewide rengeofrelativeamountsofnitrogenfixedbyvarious legumesareshowninTable2.Ifpoorgrowthofthe legumesisobtained,theamountsofnitrogenmaybe muchlessthanthosereportedhere. Theageoldquestionofwhetherornottoadd nitrogentoaleguminouscropcanbeansweredbya simplebasicconsideration.Legumesthatproducetiny seeds,suchastrueclovers,usuallyrespondtosomeN fertilizerwhentheyareveryyoung.Thenitrogen supplyintheseedsisquitesmallandyoungseedlings havealimitedrootsystemwithwhichtoabsorb nitrogen.Largerseededlegumes,suchassoybeans, havenotconsistentlyshownaresponsetoadded nitrogen.Thenitrogensupplyisgreaterinthelarger seeds,andnodulationgenerallytakesplacebeforethe seedsupplyofnitrogenisdepleted.FertilizerNitrogenThemainsourceofavailablesoilnitrogenisfrom commercialfertilizers.Nitrogenisreportedonthe Floridafertilizertaginfourdifferentforms: NitrateNitrogen(NO3 -): Thisformofnitrogenis immediatelyavailabletoplants.Nitrateisquite soluble,isnotheldbysoilcolloids,moveswiththe soilwater,andisreadilyleached.Theprincipalform ofnitrogentakenupbyplantsisnitrate. Table2. Amountsofnitrogenfixedbywell-nodulated legumes Crop NitrogenFixedPerCropYear lbs/acre Alfalfa 120-170 Clover 50-200 CrimsonClover 140-200 Vetch 80-180 Soybeans 60-100 VelvetBeans 140-210 Beans 180-200 Cowpeas 60-90 Lupines 90-150 OverallAverage: 120 AmmoniacalNitrogen(NH4 +): WhenammoniacalNis addedtothesoil,itmaybeimmediatelyabsorbedby theclayandorganiccolloids.Aslongasitremainsas ammonium,itisheldagainstleachingunlessthesoil hasextremelylowcationexchangecapacity.However, bacteriaimmediatelybegintotransformammonium tonitrate.Completetransformationgenerallyrequires fromonedaytotwoweeks,dependingonthe environmentalconditionswhichgovernnitrification. Theoptimumconditionsfornitrificationare: Optimumtemperaturerangeis80to90 degreesF.Essentiallystopsabove125 degreesFandbelow40degreesF. Propermoisture-asoiltoowetortoodry willnotsupportnitrification.Thenumberof

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Soils,FertilizersandPlantNutrition Page3 organismsthatcarryonnitrificationfluctuates withmoisturecontent. pH-practicalrangeisbetween5.5and7.0. AtthispH,nitrificationisnotmostrapidbut isstillquitegood. WaterSolubleOrganicNitrogen: Ureaandcalcium cyanamidearetheonlytwomaterialsconsideredas watersolubleorganics.Whenureaisaddedtothe soil,theenzymeureasechangesittoammonium.This reactionisveryrapid,sinceureaseisalwayspresent insoilscontainingmicroorganisms.Thereafter,the ammoniumisnitrifiedtonitrate. WaterInsolubleOrganicNitrogen: Naturalorganicsare thewaterinsolubleorganicformsofnitrogen.They mustundergoacompletechangebeforebecoming availabletoplantsso,inthatsense,theyreleaseN slowlyoveralongperiodoftime. Slowreleasematerialssuchassulfer-coatedurea andIBDUarenotedwithanasteriskonthefertilizer labelsincetheydonotfitneatlyintotheold categoriessetintolawyearsago. Theclaimthatnaturalorganicsarelesssubjectto leachingneedsclarification.Aslongasnitrogen remainsinthewaterunsolubleorganicform,oras ammonium,itisresistanttoleaching.But,oncethis nitrogenchangestonitritesornitrates,itissubjectto leachingthesameasanynitrate-Nsource.Itis doubtfulthatnaturalorganicsourcesofNareworth thepremiumpriceoftenpaidforthem.Theprosand consofvariousNsourcesarelistedinTable3.PhosphorusManyFloridasoilsarehighinnativephosphorus. OnlythefinertexturedsoilsofnorthandwestFlorida haveatendencytofixlargeamountsofphosphorus. PhosphorusaccumulatesinmostFloridasoils. Whenacertainlevelofsoil-testextractable phosphorusisreached,noadditionalfertilizer phosphorusisneeded,exceptinfrequentlight applications.Anexcessofphosphorusnutrienthasa depressingeffectontheuptakeofironandzincand hasthepotentialtopollutegroundwaterwhenrunoff orsoilerosionoccurs. Inacidsoils,ironandaluminumfixphosphorus informsrelativelyunavailabletoplants.Thisisoneof theadverseeffectsoflowsoilpH. Mostofthephosphoruspresentinthesoilcame fromphosphorus-bearingmineralsorfrom commercialfertilizers.Whenrecommendedliming practicesarefollowed,littleornophosphorusislost byleaching.Phosphoruswillleachinstronglyacid sands(pH<5.0)thatarelowinironandaluminum. Thelimingprogramiscloselyassociatedwith phosphorusavailability. Table3. ComparisonofOrganicandInorganicSourcesofNitrogen ADVANTAGES DISADVANTAGES OrganicNitrogen Aportionisslowlyavailable Littledangerofover-fertilizing Micronutrientsarepresentinmostmaterials Goodfertilizerconditioners Expensive Lownitrogencontent MaynotnitrifywhenNneededmost Lowefficiency InorganicNitrogen&Urea Lessexpensivethannaturalorganics Verysoluble Readilyavailable Canbeusedinliquidfertilizers Greaterefficiency Improperusemaydamageplants Moreleachingpotential Maybeacid-forming Moreacid-formingperpoundofmaterial(notsoper poundofnitrogencontained) Poorfertilizerconditioner

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Soils,FertilizersandPlantNutrition Page4PotassiumPotassiumdiffersfromotherplantnutrientsin thatitdoesn'tenterthestructureoftheplant.The potassiumremainsintheplantsapandiseasily leachedfromdeadplanttissue.Nodecompositionis necessarytoreleasepotassium.Plantshavea tendencytoabsorbmorepotassiumthantheyneed and,undersuchconditions,anutrientantagonism mightdevelop. Themajorportionofplantavailablepotassiumin Floridasoilscomesfromcommercialfertilizers.The amountofpotassiumreturnedtothesoilfromplant andanimalresiduesdependsonthequantityofthe residueandonitspotassiumcontent. Themajorportionofthelossofsoilpotassiumis throughcropremovalandleaching.Cropremoval accountsformostofthelossexceptwherelarge amountsofpotassiumareappliedatonetimeand leachingbecomesamajorfactor.CalciumCalcium,discussedunderliming,isgenerally appliedtothesoilaslimestoneandasimpuritiesin fertilizers.Withfewexceptions,calciumwillnotlimit productiononsoilswithpH>5.5.MagnesiumThiselementisfrequentlydeficientinFlorida soilsandadditionoffertilizermagnesiumisoften needed.Mgcanbeeconomicallysuppliedindolomite whenlimeisneeded,butanothersourcemustbe usedifthesoilpHdoesnotmeritliming.SulfurTwofairlyrecentdevelopmentshavereducedthe sulfuraddedtoagriculturallands:(1)useofhigh analysisfertilizerswhichcontainlittleornosulfur contaminants,and(2)reductionofairpollutants whichcontainedsignificantamountsofS.Asaresult, fertilizerSisnowrecommendedforcertaincrops wheredeficiencieshavebeennoted.FERTILIZERSDefinitionsofseveralcommonfertilizerterms maybeappropriatesincefrequentmisuseisobserved. Someofthetermsareburdenedwithconceptswhich shouldhaveceaseduselongagobutwhicharekept aroundbecauseoftheirpresenceinfertilizerlaws.GradeTheguaranteedpercentagesofnitrogen, phosphorus,andpotassiuminafertilizer.The elementsareexpressedintermsofN,P2O5,andK2O, inthatorder.Thoughphosphorusandpotassiumare notpresentintheoxideform,theircontentsremain expressedthatwaybecausecustom,law,and widespreadusagehaveresistedchangetothe elementalmodeofexpression.Examplesofgrades are:5-10-12,0-14-18,10-0-10,0-0-60.CompleteFertilizerAnunfortunatetermwithwhichweareburdened. Avoidusingit.Insteaduse"N-P-Kfertilizer".Thisis anyfertilizerwhichcontainsappreciablequantitiesof nitrogen,phosphorus,andpotassium.BulkBlendedFertilizerAphysicalmixtureoftwoormorefertilizer materials,usuallypreparedlocallytothe specificationsoftheclientandappliedbyspreader truck.Over70%ofthefertilizersoldinFloridais bulkblended.ChemicalCompositionsThechemicalcompositionsofsomefertilizer materialsareshowninTables4and5.Itmustbe notedthattheseareaveragevaluesandsome deviationinnutrientcontentisnormal.Allfertilizers soldarecoveredbytheFloridaFertilizerLaw.A fertilizertagwhichshowstheguaranteedanalysis mustaccompanythefertilizer.The"approximate calciumcarbonateequivalent"isameasureofthe acid-formingpotentialofthefertilizer.Aminussign indicatesthenumberofpoundsofcalciumcarbonate neededtoneutralizeacidformedwhenonetonofthe materialisaddedtothesoil.

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Soils,FertilizersandPlantNutrition Page5 Table4. Plantnutrientcontentofsomefertilizermaterials Material Percentageof: Approx.Calcium Carbonate Equivalent(CCE) Salt Index N P2O5 K2O OtherNutrients SOURCESOFONEMACRONUTRIENT Ammonia,anhydrous 82 -------2960 47 Ammonia,Aqua16-25---------720to-1080 --Ammoniumnitrate 33-34 ----0.01Zn -1180 105 Nitrogensolutions21-49---------750to-1760 70-77 Phosphoricacid --52-60 -----1000to-1400 --Potassiumchloride (muriateofpotash) ------60-620.1Mg,0.03B,47Cl0 109-116 Sodiumnitrate 16 --0.2 0.07S,0.07Cu,0.01 B +580 100 Sulfur ---------30-99S -1900to-6320 --Urea 46 -------1680 75 Urea-form 38---------1360 --SOURCESOFTWOORMOREMACRONUTRIENTS Ammonium nitrate-lime 20 ----7.3Ca,4.4Mg,4S 0 61 Ammoniumsulfate21------23S,0.1Zn,0.3Cu-2200 69 Ammoniumsulfate nitrate 26 ----15S -1700 --Ammonium phosphatenitrate 2715-------1240 --Ammonium phosphatesulfate 13-16 20-39 0.2 0.1Mg,15S,0.2 Mn,0.02Zn,0.02 Cu,0.03B -1520to-2260 --Ammonium phosphate,mono 11480.21.1Ca,0.3Mg,2.2 S,0.03Mn,0.03An, 0.02Cu,0.02B -1300 34 Ammonium phosphate,di 16-21 48-53 -----1250to-1550 30 Basicslag,open hearth ---8-12---29Ca,3.4Mg,0.3S, 2.2.Mn +1000 --Calciumcyanamide 21 ----38Ca,0.06Mg,0.3 S,0.04Mn,0.02Cu +1260 31 Calciumnitrate15------19Ca,1.5Mg,0.02 S +400 52 Colloidalphosphate --25 --------Dolomite ---------21Ca,11Mg,0.3S, 0.11Mn +1960 0.8 Gypsum ----0.5 22Ca,0.4Mg,17S 0 8 Kieserite(emjeo)---------1.6Ca,18.2Mg0 ---

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Soils,FertilizersandPlantNutrition Page6 Material Percentageof: Approx.Calcium Carbonate Equivalent(CCE) Salt Index N P2O5 K2O OtherNutrients SOURCESOFTWOORMOREMACRONUTRIENTS(continued) Limestone(calcite) ----0.3 32Ca,3Mg,0.1S, 0.5Mn,0.05Zn +1800 5 Magnesiumsulfate---------2.2Ca,10.5Mg,14 S 0 --Nitrateofsoda potash 15 --14 0.13B +550 --Potassiummagnesium sulfate ------2211Mg,23S0 43 Potassiumnitrate 13 --44 0.4Mg,0.2S,0.1B +520 74 Potassiumsulfate------501.2Mg,18S 0 46 Superphosphate, ordinary --18-20 0.2 20Ca,0.2Mg,12S 0 8 Superphosphate, concentrated --42-50 0.4 14Ca,0.3Mg,1.4S, 0.01Mn,0.01Cu, 0.01B 0 10 MuchoftheinformationinTables4and5was Table5. Additionalmicronutrientsources MATERIAL Percentageof: Mn Zn Cu Fe B S Borax --------11 --CopperSulfate -----25-35-----12-14 IronSulfate ------20 --10-14 ManganeseOxide 41-68------------ManganeseSulfate 23-28 --------12-16 Solubor ----------20 --ZincOxide --50-80 --------ZincSulfate ----------12-18 obtainedfrom"TheFertilizerHandbook",published byTheFertilizerInstitute,Washington,DC. Nutrientcontentsofnon-manufacturedmaterials usedasfertilizersarelistedinTable6.Thesemaybe usedbypersonswantingtouseonlynaturally occurringmaterials,asinthecaseofthepopularbut misnamed"organic"farmersorgardeners. Somehandyconversionfactorsarepresentedin Table7.ANIMALMANURESManureshavebeenusedasfertilizersfor centuries.Althoughtheirplantnutrientcontentis generallylow,manurescontainsomequantitiesofall oftheessentialelements.Inmanysituations,the applicationofevenamodestquantityofmanure

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Soils,FertilizersandPlantNutrition Page7 providesenoughofadeficientnutrient(especiallya micronutrient)todramaticallyincreaseplantgrowth. Thenutrientcontentofmanureisquitevariable. Table6. Plantnutrientcontentofsomenon-manufacturedmaterialsusedasfertilizer Material AveragePercentageof: N P205 K50 Ca Mg S Mn Zn Cu B Sodiumnitrate,Chilean 16 --0.2 0.1 0.05 0.07 ----0.07 0.01 Blood,dried 131.50.60.240.100.170.00040.0020.0007 0.001 Bonemeal,raw 3.9 22 --22 ------------Bonemeal,steamed2.227---25----------------Castorpomace 5.2 1.8 1.1 0.41 0.32 --0.04 0.05 0.005 0.1 Cocoashellmeal 2.41.02.70.940.340.09------0.017 --Cottonseedmeal 6.4 2.6 1.7 0.24 0.42 0.30 0.002 --0.004 0.001 Dolomite ---------21110.30.11-----0.01 Limestone(calcite) ----0.3 32 3 0.1 0.48 0.05 --0.001 Gypsum ------0.5220.417----------Tankage 2.8 3.1 1.1 3.0 0.3 0.61 ----0.04 --Guano,Peruvian 12112.48.80.61.100.0190.0020.008 0.005 Potassiumchloride ----61 0.09 0.11 0.11 0.0002 0.0001 0.0001 0.02 Peat 1.90.20.21.10.360.260.0190.0040.06 0.06 Rockphosphate --32 0.2 33 0.16 --0.033 0.002 0.001 0.0003 Sewagesludge 5.65.10.41.30.570.980.0150.2----Seaweed(kelp) 0.2 0.1 0.6 2.1 0.74 1.39 0.008 0.008 0.024 0.02 Soybeanmeal 6.81.62.40.260.310.210.0020.0020.002 --Tobaccostems 2 0.7 6.0 3.6 0.36 0.38 0.032 --0.013 0.02 Tungnutmeal 4.31.71.30.460.52---0.003-------Woodashes --1.8 5.5 23 2.2 0.4 1.0 0.2 0.13 0.01 Factorsinfluencingthequalityincludetheageand kindofanimal,thefeeditconsumed,theamountand kindoflitterorbeddingused,andthemannerin whichthemanurewashandled.Representative valuesshowninTables8and9shouldbeusedonly asgeneralguidelinesandshouldnotbeusedfor makingimportantplanningormanagementdecisions. Someinterestinggeneralitiesaboutmanures: Approximately16tonsofmanure(at75% moisture)areproducedforeachtonof livestockperyear,regardlessofspecies.

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Soils,FertilizersandPlantNutrition Page8 About500poundsofabsorbentlitterare neededtoabsorb600poundsofliquidin eachtonofmanure. Additionofsuperphosphatetomanure preventslossofammoniabyvolatilization. Use40lbs/tonforhorseandsheepmanure and25to30lbs/tonforpoultry,swine,or cattlemanure.However,intensivelivestock andpoultryoperationsalreadyhaveanexcess ofPinthemanureandwouldcertainlynot addmoreevenifitsavesN.

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Soils,FertilizersandPlantNutrition Page9 Table7. NutrientConversionFactors ToConvertColumn1to Column2,MultiplyBy: Column1 Column2 ToConvertColumn2to Column1,MultiplyBy: 1.399 Ca CaO 0.7146 1.785 CaOCaCO3 0.5603 2.103 Cl KCl 0.4756 1.649 Cl NaCl 0.6065 1.205 K K2O 0.8301 1.583 K2O KCl 0.6317 2.147 K2O KNO3 0.4658 1.849 K2OK2SO4 0.5405 1.662 Mg MgO 0.6031 1.187 MgCO3CaCO3 0.8424 2.092 MgO MgCO3 0.4762 2.981 MgOMgSO4 0.3349 1.291 Mn MnO 0.7744 2.129 MnOMnSO4 0.4697 7.218 N KNO3 0.1385 6.067 NNaNO3 0.1647 1.216 N NH3 0.8225 2.857 NNH4NO3 0.3500 4.717 N (NH4)2SO4 0.2120 2.291 P P2O5 0.4364 2.498 S SO3 0.4004 2.996 S SO4 0.3338 Table8.Averagepercentagecompositionofmacronutrientsinfreshmanure TypeofManure Percentageof: N P2O5 K2O Ca Mg S Cattle 0.6 0.3 0.5 0.3 0.1 0.04 Horse 0.6 0.3 0.60.30.1 0.04 Sheep 0.9 0.5 0.8 0.4 0.1 0.06 Swine 0.6 0.5 0.40.50.1 0.1 Poultry(layers) 1.5 1.3 0.5 3 0.3 0.4 Poultry(broilers) 3.1 3.0 2.0 2 0.4 0.7

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Soils,FertilizersandPlantNutrition Page10 Table9.Percentagecompositionofmicronutrientsandmoistureinfreshmanure Typeof Manure Percentageof: Mn Zn Cu B Fe Moisture Cattle 0.003 0.002 0.0008 0.002 --80 Horse 0.0030.0020.00080.002--70 Sheep 0.003 0.002 0.0008 0.002 --65 Swine 0.00050.010.00040.00030.03 80 Poultry 0.003 0.002 0.0006 0.002 0.06 65 Table10. Thefollowingdataarepresentedto illustratethevariabilityoffreshmanures. %N %P2O5 %K2O Broiler litter range 1.7-4.8 1.1-7.1 0.6-5.0 average 3.1 3.0 2.0DETERMININGFERTILIZER REQUIREMENTS WiththeAidofSoilTestsFertilizerisneededwhenthesoilcannotsupply sufficientquantitiesoftheessentialnutrientsforthe cropbeinggrown.Fertilizerssupplementthenutrients suppliedbythesoil.Sincesoilsvarytremendouslyin theirnutrientsupplyingcapabilities,themostlogical meansofpredictingwhatcanbeexpectedfromthe soilisbytestingthesoil. Soiltestsareusefulinpredictingfertilizerneeds whenthelevelsmeasuredinthelaboratoryare relatedtocropyieldsthroughextensivefieldstudies. Thiscorrelationofsoilteststocropyieldsisprobably theleastappreciatedaspectof"soiltesting",yet withoutcorrelationsthetestvaluesperseareuseless.WithoutSoilTestsIntheabsenceofsoiltests,onecanstill sometimesestimatethefertilizerrequirements. Experiencewiththecropandsoilisusedtodecide whichnutrientelementsshouldbeaddedandthe quantitiesofeach.Thisapproachfrequentlyleadsto over-fertilizationwithsomeelementsand under-fertilizationwithothers.Incommercial agriculturewherelargesumsarespentonfertilizer,it isapoorsubstituteforsoiltesting.DIAGNOSINGNUTRIENTDEFICIENCIES INPLANTS FoliarsymptomsFoliarsymptomsofnutrientdeficienciesvary considerablybetweenplantspecies.Inaddition, insect,disease,nematode,drought,andpesticide damageoftenproducefoliarsymptoms.General descriptionsofsymptomsproducedbynutritional deficienciesshouldbeusedonlyinconjunctionwith otheravailableinformationwhentryingtodiagnose fieldproblems.TissueTestingTissuetestingisdividedintoseparatephases whicharequitedifferent.RapidtissuetestingGreentissueisusuallytakenforthistypeof analysis.Variouschemicalsincludedinthese"quick tests"areusedtotesteachelementusinggreentissue ortheextractfromgreentissue. Thesetestsmaygiveuseableinformation,but accuracyissacrificedforspeedandfield-use convenience.Confirmationusingdrytissuetestingof suspectednutritionalproblemsisrecommended.

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Soils,FertilizersandPlantNutrition Page11DrytissuetestingThistypeoftestingusuallyinvolvestheuseof driedleavesorplants.Theentiredriedleaforplant isgroundupandthetotalcontentofselected nutrientsisdetermined.Sincetissuetestingis standardized,resultsofanalysesdoneonasplit samplebydifferentlabsshouldbecomparable(thisis notgenerallythecasewithsoiltestsdueto differencesinextractants). Thereareseveraldrawbackstoleafanalysisfor estimatingfertilizerrequirements.Leafanalysisis moretimeconsumingandmoreexpensivethaneither rapidtissuetestingorsoilanalysis.Theplantpart sampledandstageofdevelopmentarecriticalto interpretationsoftheresults.FERTILIZERPLACEMENTThecharacteristicsofthesoil,thekindofcrop, andthenatureofthefertilizermaterialsshouldbe consideredwhenchoosingmethodsoffertilizer application.Pointsaboutfertilizerplacementare listedbelow: Provideadequatequantitiesofplantnutrients withintherootzone. Irregulardistributioncanlowerfertilizer efficiency. Earlystimulationoftheseedlingisusually advantageous.Atleastpartofthefertilizer shouldbeplacedwithinreachofyoung seedlingroots. Therateanddistanceoffertilizermovement dependuponthecharacterofthesoil. Nutrientelementsmaymoveupwardduring dryperiods,andmaybecarrieddownwardby rainorirrigationwater. Soil-suppliednutrientswhenindrysoilsare oflittleornobenefittotheplant. Excessiveconcentrationsoffertilizerin contactwithseed,roots,orlegumeinoculant maybeinjurious.Cropsvaryintheir tolerancetosolublefertilizersalts. Water-solublefertilizerofrelativelylowplant foodcontenthasagreatersaltcontentper unitofplantfoodandhasagreatertendency toproducesaltinjurythandoesafertilizer containingmoreconcentratedmaterials. Nitrogenandpotassiumcarriersaremore readilysolublethanphosphaticfertilizer materialsandcannotbesafelyconcentrated inaslargeamountsnearseedsorplantroots. Reductionofsoilmoisturecontentincreases theconcentrationofsaltsinthesoilsolution. Soildryingincreasesthepossibilityofinjury. Exceptinstronglyacidic,sandysoils, phosphatesmoveslowlyfromthepointof placement.Therefore,phosphaticmaterials shouldbeplacedwheretheywillbereadily reachedbyplantroots. Placementoffertilizerinbandsreduces contactwiththesoil,therebydelayingthe conversionofphosphorustoformsnot availabletoplants.Bandedfertilizerrates maybesafelyreducedbyasmuchas50% comparedtobroadcastrates.LIQUIDANDDRYFERTILIZERS COMPAREDThereisnodifferenceintheresponseobtained fromapplicationofliquidordryformulationsofthe samefertilizermaterials.Reactionswhichoccurinthe soilarethesameforbothtypesofmaterials.Aliquid materialisneithermoremobilenormoreavailable thanadryproduct.Irrigationorrainfollowing applicationofeithertypeoffertilizeraidsinplant uptakeoftheappliednutrients.