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Precision Nutrient Management: Grid-Sampling Basis

Precision Nutrient Management: Grid-Sampling Basis. Hailin Zhang and Gordon Johnson Department of Plant and Soil Sciences. Spatial variability (macro) for agronomic land use. Acquired (use induced). Influence of historical crop production on soil properties.

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Precision Nutrient Management: Grid-Sampling Basis

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  1. Precision Nutrient Management:Grid-Sampling Basis Hailin Zhang and Gordon Johnson Department of Plant and Soil Sciences

  2. Spatial variability (macro) for agronomic land use. • Acquired (use induced). • Influence of historical crop production on soil properties. • Alfalfa vs. wheat for acidification and soil organic matter. • Fertilizer use and change in soil fertility (Garfield County).

  3. Acquired spatial variability (macro). C.V. = 54

  4. Garfield Co. Farmer’s Use of Soil Testing and Fertilization Previous Grain Normal Fertilization Soil Test Results Acres Soil Test Yield N P O K O pH N P K 2 5 2 Sur Sub 86* 1981 35 100 46 4.5 24 54 106 445 118* 1981 25 100 46 4.9 53 108 88 411 30* 1989 34 100 46 5.1 44 43 75 377 65* 26 100 46 4.4 115 118 159 752 50 1981 29 100 46 5.5 0 70 44 551 *Savings from no fertilizer to four fields = 299 acres X $24.50/acre, = $7,325 Acquired spatial variability (macro).

  5. Terrace 4 Upland Terrace 5 Terrace 3 Field Average Field Range pH=5.7 BI = 6.9 N = 20 P = 23 K = 397 pH=5.4 BI = 6.8 N = 20 P = 31 K = 522 pH=5.5 BI = 6.7 N = 12 P = 32 K = 423 pH=4.6 BI = 6.8 N = 16 P = 65 K = 310 “Bad Spot” pH=5.2 BI = 6.8 N = 14 P = 49 K = 408 pH=4.6-5.7 BI = 6.6-7.0 N = 10-20 P = 23-93 K = 310-522 pH=7.3 BI = -- N = 67 P = 22 K = 343 Terrace 2 Terrace 1 Bottom pH=5.3 BI = 6.9 N = 10 P = 44 K = 415 pH=5.2 BI = 7.0 N = 13 P = 54 K = 354 pH=4.9 BI = 6.6 N = 10 P = 93 K = 435 Acquired spatial variability (micro).

  6. Acquired spatial variability (micro). “Cow Pocks” in wheat pasture

  7. Acquired spatial variability (micro).

  8. Precision Nutrient ManagementStrategies Grid soil sampling Apparent Electrical Conductivity Yield monitor/mapping Sensing techniques

  9. Purposes of Soil Sampling Measure the nutrient content or availability of the soil Identify nutrient deficiencies Predict crop response to added nutrients Build a nutrient management plan

  10. Recognize Field Nutrient Variability Nitrate - Nitrogen lbs/acre 0-30 31-40 41-50 51-60 61-80 >80 (Nitrate-N within a 75’ x 75’ plot)

  11. Limiting Factors for Crop Growth Factors are different for every field, therefore, remediation should be different too Factors change from year to year Factors limiting yield will interact

  12. Considerations for Soil sampling Strategies Locate variability responsive to fertilizer and lime Obtain a sample that accurately represents the area sampled Balance cost of sampling with the value of information

  13. The greatest potentialfor error in soil testingis in taking the sample

  14. Soil Sampling Strategies * * * * Whole field composites: Composite sample representing the average nutrient status of the field * * * * * * * * * *

  15. 20 cores are needed to make a representative composite sample in order to get reliable soil test results

  16. Soil Sampling Strategies 2. Zone composites: Break field based on known or expected source of variability

  17. Soil Sampling Strategies 3. Grid Sampling: Break field based on ordered pattern Grid cell method: similar to whole field Grid center method: point sampling X X X X X X X X X X X X X X X X X X X

  18. Field Soil Sampling, Soil Testing, and Making Fertilizer Recommendations Exercise 1. Random sampling of the entire field , 25 cores of soil from a 0-6” depth filling two soil sample bags from the composite mixture 2. Grid-cell sampling 15 cores of soil from a 0-6” depth 3. High resolution 15 cores of soil from a 0-6” depth

  19. Whole field • 1 acre grid • Sub-grid X X X X X X X X X X X X X X X

  20. Whole field sample pH: Team 1: 6.0, 6.1 Team 2: 6.4, 6.4

  21. Whole field sample nitrate: Team 1: 19, 18 Team 2: 28, 28

  22. 127 Whole Field Sampling: 114 & 117, 188 & 190

  23. 188 Whole Field Sampling: 206 & 196, 186 & 180

  24. 5.6 Whole Field Sampling: 5.9 & 5.9, 5.6 & 5.6

  25. Why Account for Spatial Variability of Soil Properties Improve performance of ag. practices Either costs go down and/or returns go up Avoid over application that might be environmentally harmful

  26. Analysis Costs of Various Sampling Intensities *at $10/sample

  27. Analysis Costs of Various Sampling Intensities *at $10/sample; **at $10/hour and collecting 1 to 5 samples per hour

  28. Choosing a Soil Sampling Strategy • Level of management and the resources to account for variability • Whole field sampling most appropriate when fertility is high and variability is low • Zoning/sub-field sampling may be most appropriate when • Location of variation known • Sampling areas are large • Limited resource • Grid sampling maybe appropriate if location of variation is unknown and variable rate applicator is available, or variable changes slowly with distance

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