Split application of sulfur and potassium and their leaching potential for corn grown on irrigated soils

Abstract

Irrigated coarse textured soils have the potential to produce high yielding crops but are also likely to leach out fertilizer nutrients before they can be utilized. Few studies have considered split fertilizer applications of sulfur (S) and potassium (K) on coarse textured soils. Eight fertilizer studies, four S and four K, were conducted to assess how split applications of S and K fertilizers affect plant uptake, corn grain yield, and the leaching potential over the growing season. Each site had four at planting (AP) and four in-season (IS) fertilizer rates applied for a combination of 16 different fertilizer treatments. Various plant tissue, remote sensing readings, and soil samples were taken to assess nutrient availability and movement through the soil profile. Suction cup lysimeters were used in select treatments to monitor soil pore water concentrations. Single or split applications of S and K fertilizers did not increase grain yield. Significant differences among different AP and IS rates were found for early plant and ear leaf S and K concentrations, but these were unable to predict grain yield. Normalized difference vegetation index or SPAD chlorophyll readers did not prove to be indicators of final corn grain yield in either S or K studies. Plant NDVI data was able to predict biomass in K studies. Lysimeter data from S studies suggest increased S concentration towards the end of the growing season but provided no advantage of split application of S fertilizer to avoid S losses. Lysimeter data suggested early season K movement and in most sites and IS fertilizer application had the greatest effect on end of the growing season pore water K concentration. Because of potential early K movement, split applications may be advised for farmers growing corn on coarse textured soils to avoid K losses.