2.  Errors or differences in Soil samples ◦ Collection method > laboratory ◦ Environment > laboratory  Field Variability ◦ Composite sample no matter area is an AVERAGE ◦ Average of highs and lows  #of Cores ◦ 15 to 20 for each management area  Depth ◦ Nutrients can change with depth (P and pH) ◦ No-till and pasture systems ◦ Crop: bermudagrass, wheat, cotton

3.  Impact on soil sampling  Zone Management ◦ What is your Goal? ◦ What is the Product? ◦ Yield Based ◦ Topography based ◦ Soil based  Grid Soil Sampling ◦ What is the Goal? ◦ What is the product? ◦ Is it worth the money?

4.  Soil EC is soil electrical conductivity– a measurement of how much electrical current soil can conduct. It’s an effective way to map soil texture because smaller soil particles such as clay conduct more current than larger silt and sand particles. Soil EC measurements have been used since the early 1900’s-  Veris mobilized the process and added GPS. As the Veris EC cart is pulled through the field, one pair of coulter-electrodes injects a known voltage into the soil, while the other coulter-electrodes measure the drop in that voltage.  The result: a detailed map of the soil texture variability in the crop rooting zone

5.  RTK Elevation  Ran Veris EC Rig  Grid Soil Sampled at 2.5 ac Resolution ◦ Basic, Secondary, Micro, & OM  Will/have collect Yield Monitor data  Will/have apply test strips across each field to measure the variation in response to nutrients added. ◦ Supported by the Oklahoma Soybean Board.

9. Buffer Index Lime required (tons 100% ECCE) pH 6.8pH 6.4 Over 7.1None 7.10.5None 7.00.7None 6.91.0None 6.81.20.7 6.71.41.2 6.61.91.7 6.52.52.2 6.43.12.7 6.33.73.2

10. Soil Test P Index % Sufficienc y P2O5 lbs/a c 02580 104560 208040 308530 409020 65+1000

11. Soil Test K Index % Sufficienc y K2O lbs/a c 05060 757050 1258040 2009520 250+1000

12.  Using 1 factor to determine other unrelated factors

13. Buffer Index Lime required (tons 100% ECCE) pH 6.8pH 6.4 Over 7.1None 7.10.5None 7.00.7None 6.91.0None 6.81.20.7 6.71.41.2 6.61.91.7 6.52.52.2 6.43.12.7 6.33.73.2

14. Soil Test P Index % Sufficienc y P2O5 lbs/a c 02580 104560 208040 308530 409020 65+1000

27. N-Rich Strip NRSNRS NRSNRS NRSNRS NRSNRS NRSNRS NRSNRS NRSNRS NRSNRS

28.  All techniques are potentially the right way and the wrong way. ◦ Zone Management. Better than field management. But…..  MUST have variability before you treat for variability!  Variable Rate Lime, Most economical.  Sometimes Nutrient distribution is the same sometimes its not, more often its not.  Look at the cost of the method versus the economics of the production system.