soil sampling and nutrient recommendations soil education short course

Soil Sampling and Soil Sampling and Nutrient Nutrient

RecommendationsRecommendations

Soil Education Short CourseSoil Education Short Course

OutlineOutline

How to take a soil sampleHow to take a soil sampleWhat is the appropriate depth for soil testsWhat is the appropriate depth for soil tests

How many should you takeHow many should you take

How often should we sampleHow often should we sample

Preparing samples for lab analysisPreparing samples for lab analysis

Good or not-so-good soil testsGood or not-so-good soil tests

Nutrient RecommendationsNutrient RecommendationsN recommendation ModelN recommendation Model

P and K (Sufficiency and Build-Maintain)P and K (Sufficiency and Build-Maintain)

Why Should We Soil Why Should We Soil Test?Test?

Determine plant available nutrients Determine plant available nutrients in soilin soil

Estimate crop responses to nutrient Estimate crop responses to nutrient additionsadditions

Record long-term soil fertility trendsRecord long-term soil fertility trends Problem solvingProblem solving Generate nutrient recommendationsGenerate nutrient recommendations Make financial decisionsMake financial decisions

Appropriate Soil Sample Appropriate Soil Sample DepthDepth

Consistently take samples from the Consistently take samples from the same depthsame depth

6 inch sample – P, K, pH, Organic 6 inch sample – P, K, pH, Organic MatterMatter

Approximate depth of historical tillageApproximate depth of historical tillage

24 inches – Nitrate, Chloride, Sulfate24 inches – Nitrate, Chloride, Sulfate

Mobile nutrients can be taken up from Mobile nutrients can be taken up from deeper in the soildeeper in the soil

Number of Soil SamplesNumber of Soil Samples

Number of soil samples for specific Number of soil samples for specific accuracyaccuracy

pHpH PP KK OMOM

+/-+/- ## +/-+/- ## +/-+/- ## +/-+/- ##

0.10.1 337337 11 337337 1010 164164 0.10.1 8989

0.20.2 8585 55 1414 2525 2727 0.20.2 2323

0.30.3 3838 1010 44 5050 77 0.30.3 1010

0.40.4 2121 1515 22 100100 22Kansas State University

Number of composite samples Number of composite samples submitted to the lab depends on submitted to the lab depends on management areasmanagement areas

15-20 subsamples for each 15-20 subsamples for each composite samplecomposite sample


Number of composite samples may Number of composite samples may depend on field variabilitydepend on field variability

Identify management zones Identify management zones





Creek

Slope

Low land




Creek

Slope

Low land Sand

y Loam

Sandy Loam

Silt Loam


Grid soil samplingGrid soil samplingRequires more samples and ultimately Requires more samples and ultimately more costmore cost

60 ac field divided into ~2 ac grids60 ac field divided into ~2 ac grids

Grid Soil SamplingGrid Soil Sampling

May be beneficial in highly variable May be beneficial in highly variable fieldsfields

GPS and precision application GPS and precision application equipment make this possibleequipment make this possible

How Often Should We How Often Should We Sample Sample

Every year until a history is Every year until a history is establishedestablished

Historical trends is a strong point of soil Historical trends is a strong point of soil testingtesting

Generally recommended every 3-4 Generally recommended every 3-4 yearsyears

Time →

Soil

Test

→

Crop Removal < Fertilizer

Crop Removal > Fertilizer

Preparing Samples for Preparing Samples for LabLab

Know your objectivesKnow your objectivesLaboratory data is only as good as the Laboratory data is only as good as the sample submitted – regardless of the labsample submitted – regardless of the lab

Combine subsamples into composite Combine subsamples into composite samplessamples

Keep uniform depth and mix thoroughlyKeep uniform depth and mix thoroughly

Avoid contamination – buckets used for Avoid contamination – buckets used for mixingmixing

Know how much sample to submit – a Know how much sample to submit – a sandwich bag is usually enoughsandwich bag is usually enough

Lubricants for Soil Lubricants for Soil Sampling?Sampling?

Drying samplesDrying samplesNot necessary except nitrate samples Not necessary except nitrate samples that are not submitted immediatelythat are not submitted immediately

Nitrate – lay out on paper, turn on fanNitrate – lay out on paper, turn on fanDon’t – put it in the oven or microwave itDon’t – put it in the oven or microwave it

Freezing is an option for nitrate Freezing is an option for nitrate samplessamples

Fill out paperwork including Fill out paperwork including relevant historical informationrelevant historical information

Preparing Samples for Preparing Samples for LabLab

Sample Information Sample Information SheetSheet

Where To Send Your Where To Send Your SamplesSamples

Your objectives! What is important?Your objectives! What is important?Tests appropriate for your areaTests appropriate for your area

Accurate resultsAccurate results

Turn around timeTurn around time

CostCost

ServiceService

Part of a government program?Part of a government program?Ask your local extension agent what Ask your local extension agent what tests are required – Don’t assume all tests are required – Don’t assume all labs provide the same required tests!labs provide the same required tests!

Choosing Soil TestsChoosing Soil TestspH (1:1 soil:water)pH (1:1 soil:water)

Very accurate and reliableVery accurate and reliable

Substantial research conducted on pHSubstantial research conducted on pH

Determines if lime is neededDetermines if lime is needed

pH > 7.3 – calcium carbonate present pH > 7.3 – calcium carbonate present (free lime)(free lime)

pH < 5.8 – crop response to limepH < 5.8 – crop response to lime

Buffer pH (Buffer Index)Buffer pH (Buffer Index)Very accurate and reliableVery accurate and reliable

Tells how much lime to addTells how much lime to add

SMP is most commonSMP is most common

Choosing Soil TestsChoosing Soil Tests

PhosphorusPhosphorusVariety of testsVariety of tests

Bray P-1Bray P-1Most correlation/calibration dataMost correlation/calibration data

Inaccurate on calcareous soil (reads low)Inaccurate on calcareous soil (reads low)

Olsen POlsen PSpecific to high pH soil (abundant data on Specific to high pH soil (abundant data on high pH)high pH)

Mehlich 3Mehlich 3Works on a wide range of soil pH (acid → Works on a wide range of soil pH (acid → calcareous)calcareous)

Limited correlation/calibration dataLimited correlation/calibration data

Most commonMost common


PotassiumPotassiumExchangeable ammonium acetateExchangeable ammonium acetate

Fairly good testFairly good test

Most useful for watching trends over Most useful for watching trends over timetime

NitrateNitrateKCl extractableKCl extractable

Abundant dataAbundant data

Based on expected yieldBased on expected yield

Adjusted based on organic matter, Adjusted based on organic matter, previous crop, fallow previous crop, fallow

Organic Matter (%)Organic Matter (%)Modified Walkley-Black or loss on ignitionModified Walkley-Black or loss on ignition

Reliable, consistent dataReliable, consistent data

May be inflated if crop residue is in sampleMay be inflated if crop residue is in sample

Warm season crop N adjustment = %OM×20Warm season crop N adjustment = %OM×20

Cool season crop N adjustment = %OM×10Cool season crop N adjustment = %OM×10

ZincZincDTPA extract – diethylenetriaminepentacetic DTPA extract – diethylenetriaminepentacetic acidacid

Good predictor of crop responseGood predictor of crop response

Reliable on high pH soil, less on acid soilsReliable on high pH soil, less on acid soils


SulfateSulfateCalcium phosphate extractCalcium phosphate extract

Little calibration dataLittle calibration data

Variable crop responseVariable crop response

Credit from organic matter (2.5 × % OM)Credit from organic matter (2.5 × % OM)

CEC (Cation Exchange Capacity)CEC (Cation Exchange Capacity)Measured by summation (KMeasured by summation (K++, Ca, Ca++++, Na, Na++, , HH++))

Soil’s potential to ‘hold’ nutrientsSoil’s potential to ‘hold’ nutrients

Overestimates on calcareous soilsOverestimates on calcareous soils


IronIronDTPA extractableDTPA extractable

Poor calibration dataPoor calibration data

Inadequate for acid soilsInadequate for acid soils

Limited use for calcareous soilLimited use for calcareous soil

Calcium, Magnesium, Manganese, Calcium, Magnesium, Manganese, MolybdenumMolybdenum

Poorly calibratedPoorly calibrated

Deficiency is rareDeficiency is rare


BoronBoronPoor calibrationPoor calibration

Poor soil testPoor soil test

Used for alfalfa grown on sandy soilUsed for alfalfa grown on sandy soil

CopperCopperPoor CalibrationPoor Calibration

Deficiency is rareDeficiency is rare

Occasional deficiency in wheat on Occasional deficiency in wheat on organic soilorganic soil


Exchangeable Sodium PercentageExchangeable Sodium Percentage Fairly reliableFairly reliable Diagnoses alkali/sodic soilsDiagnoses alkali/sodic soils

Soluble Salts (Electrical Soluble Salts (Electrical Conductivity)Conductivity) 1:1 soil to water paste1:1 soil to water paste Diagnoses saline soilDiagnoses saline soil


Soil Tests SummarySoil Tests SummaryGoodGood QuestionableQuestionable

pHpH CalciumCalcium

Buffer pHBuffer pH MagnesiumMagnesium

PhosphorusPhosphorus CopperCopper

PotassiumPotassium ManganeseManganese

NitrateNitrate MolybdenumMolybdenum

Organic MatterOrganic Matter

ZincZinc

ChlorideChloride

ESPESP

Soluble SaltsSoluble Salts

Sample ResultsSample Results

Nutrient Nutrient RecommendationsRecommendations

Available at:http://www.agronomy.ksu.edu/SoilTesting

Questions?Questions?

soil sampling and nutrient recommendations soil education short course

Documents

calcareous soil

soil samplewhat

soil testshow

ac gridsgrid soil samplingmay

high ph soil abundant

appropriate depth

management areas15

tests appropriate