Comparing Grid and ECa 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 (Bronson et al., 2006; Corwin and Lesch, 2005). However, the relationship between spatial variability of soil EC and crop nutrients is unclear (Johnson et al 2001; Rysan and Sarec, 2008). In this project, grid and zone nutrient management strategies are compared in peanut production. Our first objective is to relate our test site’s soil chemical and physical properties to on-the-go measurements of EC (EC_a). The second objective is to quantify variation in spatial measurements of soil nutrient levels determined using contrasting methods of soil sampling and interpolation compared to a control. These include the comparison of grid sampling by 1 hectare polygon, grid sampling with interpolation, zone sampling by EC_a determined polygons, and zone sampling with interpolation. These methods were compared to a dense sampling scheme to determine the method which yielded the most accuracy. Four peanut production fields (10 to 12 ha) were sampled in 2012 according to grid and EC_a directed management zones at the West Florida Research and Education Center in Jay, Florida. The comparison was repeated on three different fields at the West Florida Research and Education Center in 2013.  A grid size of 1 ha was assigned to each field. On-the-go measurements of soil EC were collected using the Veris 3150 (Veris Technologies, Salina, KS) and the shallow EC measurements were used to generate three management zones for each field. Soil samples from each method were analyzed for pH, texture and Mehlich 1 extractable P, K, Ca, and Mg. Results from objective one found that a poor and inconsistent relationship existed between EC_a, yield and Mehlich 1 extractable P, K, Ca, and Mg. From this we conclude that EC_a alone is not a good predictor of fertility management zones. Results from objective two found that interpolated grid sampling at a one hectare intensity most frequently provided the most accurate representation of variability of Mehlich 1 extractable P, K, Ca and Mg.

Bronson, K.F., Bookera, J.D., Bordovskya, J.P., Keelinga, J.W., Wheelera, T.A., Bomanb, R.K., Parajuleea, M.N., Segarrac, E. and   Nichols, R.L. (2006). Site-Specific Irrigation and Nitrogen Management for Cotton Production in the Southern High Plains. Agron. J. 98: 212-219.

Corwin, D.L. & Lesch, S.M. (2005). Apparent soil electrical conductivity measurements in agriculture. Computers and Electronics in Agriculture, 46: 11-43. 

Johnson, C.K., Doran, J.W., Duke, H.R., Weinhold, B.J., Eskridge, K.M., and Shanahan, J.F. (2001). Field-scale electrical conductivity mapping for delineating soil condition. Soil Sci. Soc. Am. J, 65: 1829-1837.

Rysan, L., and Sarec, O. (2008). Research of Correlation between electric soil conductivity and yield based on the use of GPS technology. Res. AGR. ENG., 54(3): 136-147.