Characterizing Spatial Variability of Phosphorus and Potassium Response in Agricultural Landscapes.

In 2012-13, Research was conducted at the Kansas State University North Central Kansas Experiment field and in cooperation with a producer in Republic County, KS, on fields characterized by high soil variability. In irrigated corn fields, the experimental design consisted of four strip-plots across a field (three P fertilizer rates and a 0 rate control. In irrigated soybean fields, treatments applied in the strip plots included P fertilizer alone, K fertilizer alone, P&K combined, and an utreated control.  Strips were replicated twice across the field.  Geo-referenced soil samples were collected at 100-foot intervals along each strip.  Geo-referenced yield was collected at the same locations.  Soil samples were analyzed for various properties that influence P availability, including: soil test P, soil pH, extractable Al, Fe, and Ca, and organic matter, as well as nitrate-N and soil test K.  Spatial analysis of P and K response will be compared to spatial distribution of soil properties.  This design will allow us to quantify crop response to P and K at varying rates, landscape positions, soil test P and K concentrations, and soil types (comprising variable soil chemical and physical properties).