Comparing Grid and Directed Zone Soil Sampling Schemes for Peanut Production.

Site specific crop management involves identifying spatial variability within a field, and using that information to implement efficient management practices. On the go measurement of soil electrical conductivity (EC) is one method of delineating management zones that seeks to improve upon the grid sampling method for nutrient management.  However, the relationship between spatial variability of soil EC and crop nutrients is unclear. In this project, grid and zone nutrient management strategies are compared in peanut production. Our first objective was to relate soil chemical or physical properties to lab and on-the-go measurements of EC. The second objective was to quantify input costs and peanut yield at field-scale for comparison of grid and zone nutrient management strategies. Four peanut production fields (10 to 12 ha) sampled according to grid and EC directed management zones at the West Florida Research and Education Center in Jay, Florida. A grid size of 1 ha was assigned to each field. On-the-go measurements of soil EC were collected using the Veris 3150 and shallow EC measurements were used to generate three management zones for each field. Soil samples from each method were analyzed for EC, pH, texture and Mehlich 1 extractable P, K, Ca, and Mg. Results, indicate a strong relationship exists between laboratory measurement of soil EC and soil extractable Ca (r² = 0.51) and Mg (r² = 0.59) concentration. A similar relationship exists between EC determined by the Veris and soil Ca (r²=.05) and Mg (r²=.15) content. Poor correlation of EC with soil P and K concentration suggest that delineating soil nutrient management zones from soil EC measurement may not be appropriate for P and K fertilizer applications.