Spatial Variability of Saline and Sodic Soils in the Northern Great Plains.

Eastern South Dakota (SD), USA agriculture is dominated by row crop production of primarily maize, soybeans, and wheat. In the past two decades, the salt-affected areas are increasing each year, though the total area is difficult to quantify. The soil salts limit and prevent crop yield of these salt-sensitive crops and cause producers to change management practices in order to maintain productivity on these salt-affected soils. The objective of this study was to identify where soil salts are located and how the salts are spatially related on a field scale, and in doing so, create management zones for mitigation. Soil cores were collected from various points across a field in Day County, SD and analyzed for total soluble salts (TSS), electrical conductivity (EC), sodium adsorption ratio (SAR), and gypsum content. These soil properties were then spatially evaluated using the ArcGIS 10.2 geostatistical analysis toolset to create semi-variograms and kriging maps. The spatial salt data was then combined with historical yield maps to generate management zones using Yield Editor 2.0. Preliminary results for EC show a nugget of 3.2 m and a sill of 12.6 m and a nugget and sill of 1.9 m and 5.8 m respectively for SAR. Because the sill is greater than the nugget, we can preliminarily conclude that spatial correlation exists for soil EC and SAR on a field scale. More data will be collected to determine the spatial dependence of the salts.