Field Scale Evaluation of Corn Response to Sulfur Applied in Starter Fertilizer.

Historically, no sulfur fertilization has been recommended for corn (Zea mays L.) production in fine textured soils in Minnesota. However, recent sulfur (S) deficiency symptoms have been documented in fine textured soils where spatial variation exists. The objectives of this study were to determine sulfur impact on corn yield response within and across fields using replicated strip trial methodology, to evaluate various factors for predicting S need, and to determine differences between soil type and landscape position in response to sulfur. Field strip trials were conducted in 2008 and 2009 at four locations with three different soil types of sandy loam (SL), clay loam (CL), and loams (Ls). Treatments in addition to 157 kg N ha^-1 and 65 kg K ha^-1 broadcast and incorporated before planting consisted of starter (applied with the planter 5 cm beside and below the seed) rates of N (22 kg N ha^-1), P (10 kg P ha^-1), and S (28 kg S ha^-1) in several combinations of N only, N+P, N+S, and N+P+S.  Two additional treatments included a no starter or S (check) and 28 kg ha^-1 S surface broadcast pre-plant (CheckS). Due to the spatial variation, average, minimum, and maximum organic matter levels  at a 0-15 cm of soil depth ranged from 0.71, 0.4, and 1.3 % for SL, 4.30, 3.0, and 5.5 % for CL, 2.0, 1.2, and 3.2 % for L (2008) and 3.9, 1.0, and 9.7 % for L (2009). The largest yield increase was observed at L (2009) from 630 to 1500 kg ha^-1 by starter sulfur fertilizer combinations. At that location, average grain uptake of S was around 0.068 % without S treatments and around 0.090 % with S applications. Data from this study indicates that targeted sulfur fertilizer application under some circumstances could lead to a potential yield increase.