Sulfur Cycling In a Wheat, Double Crop Soybean Rotation In Southwest Indiana.

Sulfur (S) is often an overlooked macronutrient in today’s agronomic cropping systems especially for cool season crops. The objective of this study was to determine optimum rates of nitrogen (N) and S in a field low in S. The field was located near Vincennes Indiana on an Ade loamy fine sand (Coarse-loamy, mixed, superactive, mesic Lamellic Argiudoll). The study was initiated with winter wheat in 2009-10 growing season followed by double-crop soybean in 2010. Experimental design was a 4 x 5 factorial with 4 replications.  Treatments were arranged in a randomized complete block design with 4 S rates of 0, 17, 34, and 50 kg S/ha and 5 N rates of 0, 45, 78, 112, and 146 kg N/ha. Biomass, grain yield, and seed mass were measured for each crop. Plant and seed tissues were analyzed for N and S. Soil samples to a depth of 90 cm in 15-cm increments were analyzed for the movement and concentration of nitrate, sulfate, and ammonium. In wheat, tissue concentrations at Feekes 6 for 17 kg S/ha and 78 kg N/ha correlated well with maximum yield and biomass production. Increased disease severity and lodging were noted at the higher N and S rates. At first bloom, soybean plant tissue was low in S following the low S applications to wheat.  However, soybean yields showed no clear relationship with the applications of N and S in wheat. Additional study results will be provided.