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Fertility Best Management Practices for Phosphorus Control on Organic Soils: Calibrated Soil Testing
http://edis.ifas.ufl.edu/ ( Publisher's URL )
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STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/IR00001221/00001
 Material Information
Title: Fertility Best Management Practices for Phosphorus Control on Organic Soils: Calibrated Soil Testing
Series Title: Fertility Best Management Practices for Phosphorous Control on Organic Soils series
Alternate Title: Fertility BMPs for Phosphorous Control on Organic Soils: Calibrated Soil Testing
Abbreviated Title: Calibrated Soil Testing
Fertility Best Management Practices for Phosphorus Control onOrganic Soils: Calibrated Soil Testing
Physical Description: Fact Sheet
Creator: Bottcher, Del
Hanlon Edward A. (Edward Aloysius) 1946-
Izuno, Forrest T.
Publisher: University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication: Gainesville, Fla.
Publication Date: 1992
 Subjects
Subjects / Keywords: Everglades Agricultural Area
Fertilizers -- Application -- Florida -- Everglades
Soils -- Testing -- Florida -- Everglades
Phosphorus -- Environmental aspects -- Florida -- Everglades
Genre:
Spatial Coverage:
 Notes
Abstract: Background -- Calibrated soil testing procedure -- References
Acquisition: Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Diana Hagan.
Publication Status: Published
General Note: "Original publication date December 1992. Reviewed July 2002."
General Note: "AGR52"
 Record Information
Source Institution: University of Florida Institutional Repository
Holding Location: University of Florida
Rights Management: All rights reserved by the submitter.
System ID: IR00001221:00001

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FertilityBMPsforPhosphorousControlonOrganicSoils:CalibratedSoilTesting Page2 fieldshouldbecarriedout.Areasofdifferent croppingandmanagementhistoryandsoiltypes shouldalwaysbesampledseparately.Untilsampling dataareavailabletoprovetheuniformityofa managementarea,samplingshouldbedoneforareas nogreaterthana1/4sectionandpreferablyatthe40 acreblocklevel. Bandingoffertilizerstypicallydoesnotpresenta significantproblemfortheuseofaCST.Forthe mostpart,practicesincludetillageafterharvestinga cropwhichhasreceivedbandedfertilizerplacement. Thispracticeusuallymixesthesoilsufficientlysothat thebandsarenolongeraconcern.Thepresenceof bedsforlettuceproduction,acropwithdefinite phosphorussavingsforbanding(about50%),also meansextrasoilmixingwhenthebedsaredestroyed forsubsequentcrops(see BandingofFertilizer). StepTwo. Developmentofyieldresponsecurvesis themostcostlyandtimeconsumingphaseinthe developmentofaCalibratedSoilTest,butitisalso themostimportantphase.Thecurveisdevelopedby conductingmultiplefieldfertilityexperimentson fields/plotsthathavehadsoilsamplingdonepriorto fertilization.Itisbesttouseseveralgroupsof fields/plotswithdifferentpre-fertilizationsoil phosphoruslevels(rangingfromverylowtovery high)andtohaveenoughfields/plotswithineachsoil phosphorusleveltodetermineanaccurateyield responsecurve.Examplesofyieldresponsecurves fortwopre-fertilizationsoilphosphoruslevelsare showninFigure1(Hanlon,et.al.,1990). Thecropyieldresponsefigureintroducesthe problemsofinterpretations.ThelineforeachprefertilizationsoilphosphoruslevelinFigure1isa linearconnectionofthemeans.However,thecurrent "bestapproach"isbelievedbymanytobetheuseof bothalinearplateauandasimplequadratic regression.Thezoneofphosphorusrateswithinthe criticalpointofthelinearplateaumodelandthe maximumofthequadraticmodelcontainsthelower andupperbounds,respectively,foraphosphorus recommendation.RhoadsandHanlon(1990)trieda probability-of-responseapproachwithsnapbeansand thatthecurrentinterpretationandrecommendations (Hanlon,etal.,1990)wereappropriate. Thebottom-lineisthatthedatavariabilitywithin responsecurvespreventsaccurateinterpretationofan optimalfertilityratewhichideallywouldbebasedon thepointwherethemarginalcostoffertilization becomesequalwiththemarginalrevenuefrom increasingyield.Anacceptedprocedure(usedby IFAS'sGainesvilleSoilsLab)istoplotsoiltestlevels versuscropresponseat0Prate(thiscurvewould lookverymuchlikethoseinFigure1withsoiltest levelonthebottomaxis).Thesoiltestlevelsare groupedintoratingsof"very,low,....,high,veryhigh" andspecificrecommendationsaremadebycrop. Anotherapproachwouldbetoplottheoptimalor "bestapproach"fertilizationratefromeachofthe individualyieldresponsecurves(Figure1)againstthe pre-fertilizationsoil-testPleveltoproducetheCST responsecurve(Figure2).ThelineinthisCSTcurve impliesanaccuracygreaterthanisknownsogrouping intoratingasaboveisstillappropriate.This approachdiffersonlyinthepresentation.Both approachesusethephilosophyoffertilizationthe cropandnotthesoil.TheCSTresponsecurvesby eitherapproachcanthenbeusedtomakefuture fertilizerrecommendationsbasedonsoil-testvalues andcroptypealone.Itisimportanttore-emphasize thattheoptimalfertilizationrateoccursnotwhere theyieldismaximized,but,rather,wherethe marginalcostofaddingmorefertilizerequalsthe marginalrevenuegainedbytheincreasedyield.This pointwillalwaysbereachedbeforemaximumyieldis attained.However,duetotheuncertaintyintheCST curves,itisgenerallybettertoselecttheoptimal fertilityrateasthepointwheretheyieldresponse curvebeginstoflattenoffwhichmorespecifically definedinthe"bestapproach"usedabove. TheappropriatelaboratorysoilPextraction procedureforestimatingtheactualamountofPina soilsampleavailabletoacropvariesaccordingtosoil properties.TheCSTshavebeendevelopedfor mineralsoilsusingMehlich-1anddoubleacid extractantsandfororganicsoilsusingawater extraction(Pw).UsingPwonmineralsoilsisnot recommendedbyIFASbecauseitisuncalibrated. UsingMehlich-1onorganicsoilsisnotrecommended byIFASbecauseithasbeenonlymarginally calibrated.Espinoza(1992)foundthattheMehlich-3 mightbebetterthaneithertheMehlich-1orthePw, butadditionalworkisneeded. Forfurtherinformationonsoiltesting,contact theSoilTestingLaboratoryattheEverglades AgriculturalResearchandEducationCenter.

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FertilityBMPsforPhosphorousControlonOrganicSoils:CalibratedSoilTesting Page3 Specificsoilsampling,soiltesting,andfertilizer recommendationscanbefoundinCircular817 (Hanlon,etal.,1990)andtheSugarcaneGrowers NewsletterbyCoale(1989).REFERENCESCoale,F.J.1989. SoilSampling,SoilTestingand FertilizerRecommendationsforFloridaSugarcane. SugarcaneGrowersNewsletter.3(1):1-4.Fla. CooperativeExtensionService.BelleGlade,FL. Figure1. .HypotheticalcropyieldresponseforPfertilizationfortwogivensoilPlevels

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FertilityBMPsforPhosphorousControlonOrganicSoils:CalibratedSoilTesting Page4 Figure1. Hypotheticalcalibratedsoiltest(CST)responsecurvetoprovideoptimalyieldresponsefor agivensoiltestlevel.