SLIDE 1
Soil Sampling and Nutrient Soil Sampling and Nutrient Recommendations Recommendations
Kent Martin Kent Martin SW Agronomy Agent Update SW Agronomy Agent Update 12/1/2009 12/1/2009
SLIDE 2 Outline Outline
How to take a soil sample How to take a soil sample
What is the appropriate depth for soil tests What is the appropriate depth for soil tests How many should you take How many should you take How often should we sample How often should we sample Preparing samples for lab analysis Preparing samples for lab analysis Good or not Good or not-
so-
good soil tests
Nutrient Recommendations Nutrient Recommendations
N recommendation Model N recommendation Model P and K (Sufficiency and Build P and K (Sufficiency and Build-
Maintain)
SLIDE 3 Why Should We Soil Test? Why Should We Soil Test?
Determine plant available nutrients in soil Determine plant available nutrients in soil Estimate crop responses to nutrient additions Estimate crop responses to nutrient additions Record long Record long-
- term soil fertility trends
term soil fertility trends Problem solving Problem solving Generate nutrient recommendations Generate nutrient recommendations Make financial decisions Make financial decisions
SLIDE 4
Appropriate Soil Sample Depth Appropriate Soil Sample Depth
Consistently take samples from the same depth Consistently take samples from the same depth
6 inch sample 6 inch sample – – P, K, pH, Organic Matter P, K, pH, Organic Matter Approximate depth of historical tillage Approximate depth of historical tillage 24 inches 24 inches – – Nitrate, Chloride, Sulfate Nitrate, Chloride, Sulfate Mobile nutrients can be taken up from deeper in the Mobile nutrients can be taken up from deeper in the soil soil
SLIDE 5 Number of Soil Samples Number of Soil Samples
Number of soil samples for specific accuracy Number of soil samples for specific accuracy 2 2 100 100 2 2 15 15 21 21 0.4 0.4 10 10 0.3 0.3 7 7 50 50 4 4 10 10 38 38 0.3 0.3 14 14 337 337 # # 5 5 1 1 +/ +/-
P 85 85 337 337 # # 23 23 0.2 0.2 27 27 25 25 0.2 0.2 89 89 0.1 0.1 164 164 10 10 0.1 0.1 # # +/ +/-
# +/ +/-
+/-
OM K K pH pH
Kansas State University
SLIDE 6 Number of composite samples submitted to the Number of composite samples submitted to the lab depends on management areas lab depends on management areas 15 15-
- 20 subsamples for each composite sample
20 subsamples for each composite sample
Number of Soil Samples Number of Soil Samples
SLIDE 7
Number of composite samples may depend on Number of composite samples may depend on field variability field variability
Identify management zones Identify management zones
Number of Soil Samples Number of Soil Samples
SLIDE 8 Number of composite samples may depend on Number of composite samples may depend on field variability field variability
Identify management zones Identify management zones
Number of Soil Samples Number of Soil Samples
Creek Slope Low land
SLIDE 9 Number of composite samples may depend on Number of composite samples may depend on field variability field variability
Identify management zones Identify management zones
Number of Soil Samples Number of Soil Samples
Creek Slope Low land Sandy Loam Sandy Loam Silt Loam
SLIDE 10
Number of Soil Samples Number of Soil Samples
Grid soil sampling Grid soil sampling
Requires more samples and ultimately more cost Requires more samples and ultimately more cost 60 ac field divided into ~2 ac grids 60 ac field divided into ~2 ac grids
SLIDE 11
Grid Soil Sampling Grid Soil Sampling
May be beneficial in highly variable fields May be beneficial in highly variable fields
GPS and precision application equipment make this GPS and precision application equipment make this possible possible
SLIDE 12 How Often Should We Sample How Often Should We Sample
Every year until a history is established Every year until a history is established
Historical trends is a strong point of soil testing Historical trends is a strong point of soil testing
Generally recommended every 3 Generally recommended every 3-
4 years
Time → Soil Test → Crop Removal < Fertilizer Crop Removal > Fertilizer
SLIDE 13
Preparing Samples for Lab Preparing Samples for Lab
Know your objectives Know your objectives
Laboratory data is only as good as the sample Laboratory data is only as good as the sample submitted submitted – – regardless of the lab regardless of the lab
Combine subsamples into composite samples Combine subsamples into composite samples
Keep uniform depth and mix thoroughly Keep uniform depth and mix thoroughly Avoid contamination Avoid contamination – – buckets used for mixing buckets used for mixing Know how much sample to submit Know how much sample to submit – – a sandwich a sandwich bag is usually enough bag is usually enough
SLIDE 14
Lubricants for Soil Sampling? Lubricants for Soil Sampling?
SLIDE 15 Drying samples Drying samples
Not necessary except nitrate samples that are not Not necessary except nitrate samples that are not submitted immediately submitted immediately Nitrate Nitrate – – lay out on paper, turn on fan lay out on paper, turn on fan
Don Don’ ’t t – – put it in the oven or microwave it put it in the oven or microwave it
Freezing is an option for nitrate samples Freezing is an option for nitrate samples
Fill out paperwork including relevant historical Fill out paperwork including relevant historical information information
Preparing Samples for Lab Preparing Samples for Lab
SLIDE 16
Sample Information Sheet Sample Information Sheet
SLIDE 17
Where To Send Your Samples Where To Send Your Samples
Your objectives! What is important? Your objectives! What is important?
Tests appropriate for your area Tests appropriate for your area Accurate results Accurate results Turn around time Turn around time Cost Cost Service Service
Part of a government program? Part of a government program?
Ask your local extension agent what tests are Ask your local extension agent what tests are required required – – Don Don’ ’t assume all labs provide the same t assume all labs provide the same required tests! required tests!
SLIDE 18
Choosing Soil Tests Choosing Soil Tests
pH (1:1 pH (1:1 soil:water soil:water) )
Very accurate and reliable Very accurate and reliable Substantial research conducted on pH Substantial research conducted on pH Determines if lime is needed Determines if lime is needed pH > 7.3 pH > 7.3 – – calcium carbonate present (free lime) calcium carbonate present (free lime) pH < 5.8 pH < 5.8 – – crop response to lime crop response to lime
Buffer pH (Buffer Index) Buffer pH (Buffer Index)
Very accurate and reliable Very accurate and reliable Tells how much lime to add Tells how much lime to add SMP is most common SMP is most common
SLIDE 19 Choosing Soil Tests Choosing Soil Tests
Phosphorus Phosphorus
Variety of tests Variety of tests Bray P Bray P-
1
Most correlation/calibration data Most correlation/calibration data Inaccurate on calcareous soil (reads low) Inaccurate on calcareous soil (reads low)
Olsen P Olsen P
Specific to high pH soil (abundant data on high pH) Specific to high pH soil (abundant data on high pH)
Mehlich Mehlich 3 3
Works on a wide range of soil pH (acid Works on a wide range of soil pH (acid → → calcareous) calcareous) Limited correlation/calibration data Limited correlation/calibration data Most common Most common
SLIDE 20
Choosing Soil Tests Choosing Soil Tests
Potassium Potassium
Exchangeable ammonium acetate Exchangeable ammonium acetate Fairly good test Fairly good test Most useful for watching trends over time Most useful for watching trends over time
Nitrate Nitrate
KCl KCl extractable extractable Abundant data Abundant data Based on expected yield Based on expected yield Adjusted based on organic matter, previous crop, Adjusted based on organic matter, previous crop, fallow fallow
SLIDE 21 Organic Matter (%) Organic Matter (%)
Modified Modified Walkley Walkley-
- Black or loss on ignition
Black or loss on ignition Reliable, consistent data Reliable, consistent data May be inflated if crop residue is in sample May be inflated if crop residue is in sample Warm season crop N adjustment = %OM Warm season crop N adjustment = %OM× ×20 20 Cool season crop N adjustment = %OM Cool season crop N adjustment = %OM× ×10 10
Zinc Zinc
DTPA extract DTPA extract – – diethylenetriaminepentacetic diethylenetriaminepentacetic acid acid Good predictor of crop response Good predictor of crop response Reliable on high pH soil, less on acid soils Reliable on high pH soil, less on acid soils
Choosing Soil Tests Choosing Soil Tests
SLIDE 22 Sulfate Sulfate
Calcium phosphate extract Calcium phosphate extract Little calibration data Little calibration data Variable crop response Variable crop response Credit from organic matter (2.5 Credit from organic matter (2.5 × × % OM) % OM)
CEC ( CEC (Cation Cation Exchange Capacity) Exchange Capacity)
Measured by summation (K Measured by summation (K+
+, Ca
, Ca++
++, Na
, Na+
+, H
, H+
+)
) Soil Soil’ ’s potential to s potential to ‘ ‘hold hold’ ’ nutrients nutrients Overestimates on calcareous soils Overestimates on calcareous soils
Choosing Soil Tests Choosing Soil Tests
SLIDE 23
Iron Iron
DTPA extractable DTPA extractable Poor calibration data Poor calibration data Inadequate for acid soils Inadequate for acid soils Limited use for calcareous soil Limited use for calcareous soil
Calcium, Magnesium, Manganese, Molybdenum Calcium, Magnesium, Manganese, Molybdenum
Poorly calibrated Poorly calibrated Deficiency is rare Deficiency is rare
Choosing Soil Tests Choosing Soil Tests
SLIDE 24
Boron Boron
Poor calibration Poor calibration Poor soil test Poor soil test Used for alfalfa grown on sandy soil Used for alfalfa grown on sandy soil
Copper Copper
Poor Calibration Poor Calibration Deficiency is rare Deficiency is rare Occasional deficiency in wheat on organic soil Occasional deficiency in wheat on organic soil
Choosing Soil Tests Choosing Soil Tests
SLIDE 25
- Exchangeable Sodium Percentage
Exchangeable Sodium Percentage
Fairly reliable
Diagnoses alkali/sodic sodic soils soils
- Soluble Salts (Electrical Conductivity)
Soluble Salts (Electrical Conductivity)
1:1 soil to water paste
Diagnoses saline soil
Choosing Soil Tests Choosing Soil Tests
SLIDE 26
Soil Tests Summary Soil Tests Summary
Soluble Salts Soluble Salts ESP ESP Chloride Chloride Zinc Zinc Organic Matter Organic Matter Molybdenum Molybdenum Nitrate Nitrate Manganese Manganese Potassium Potassium Copper Copper Phosphorus Phosphorus Magnesium Magnesium Buffer pH Buffer pH Calcium Calcium pH pH Questionable Questionable Good Good
SLIDE 27
Sample Results Sample Results
SLIDE 28 Nutrient Recommendations Nutrient Recommendations
Available at: http://www.agronomy.ksu.edu/SoilTesting
SLIDE 29
Nutrient Recommendations Nutrient Recommendations
SLIDE 30
Nutrient Recommendations Nutrient Recommendations
SLIDE 31 Nutrient Removal Nutrient Removal
Crop Unit P2O5 K2O
Alfalfa lbs/ton 12.00 60.00 Red clover lbs/ton 12.00 50.00 Bermudagrass lbs/ton 12.00 40.00 Bromegrass lbs/ton 12.00 40.00 Fescue, tall lbs/ton 12.00 40.00 Corn lbs/bu 0.33 0.26 Corn silage lbs/ton 3.20 8.70 Grain sorghum lbs/bu 0.40 0.26 Sorghum silage lbs/ton 3.20 8.70 Wheat lbs/bu 0.50 0.30 Sunflowers lbs/cwt 1.50 0.60 Oats lbs/bu 0.25 0.20 Soybeans lbs/bu 0.80 1.40 Native grass lbs/ton 5.40 30.00
SLIDE 32 Nutrient Removal Nutrient Removal
Example Example
Assume 50 Assume 50 bu bu/ac wheat /ac wheat 50 50× ×0.5 = 25 lb P 0.5 = 25 lb P2
2O
O5
5/ac removed
/ac removed 50 50× ×0.3 = 15 lb K 0.3 = 15 lb K2
2O/ac removed
O/ac removed 5 years of production without fertilization 5 years of production without fertilization
125 lb P 125 lb P2
2O
O5
5/ac removed
/ac removed 75 lb K 75 lb K2
2O/ac removed
O/ac removed
SLIDE 33
Questions? Questions?
