The use of differential GPS in field data extraction and spatially variable fertilizer application

Practical feasibility tests on the use of differential Global Positioning System (DGPS) in the agricultural environment for field data extraction, and, spatially variable (SV) fertilizer application control, were carried out. Using DGPS, soil sample maps were generated and the data interpolated to the required resolution using the Kriging interpolation technique. It was shown how the generation of semivariogram plots (for Kriging) could be used for the extraction of soil data, and could assist in determining the effectiveness of SV control in the correction of certain nutrient levels. Yield maps were also generated and various processing considerations were outlined for this purpose. High degrees of variation were seen to exist in areas originally considered to be fairly homogeneous in nature. Even when other physical effects (such as the hydrography of the field) were considered, the variations that exist are a strong motivation for the need for SV agricultural practice.