Monday, November 5, 2007
40-2
Sulfur and Nitrogen Starter Fertilizer for Soybean in Michigan.
B.E. Daley, R.J. Gehl, D.D. Warncke, and K.D. Thelen. Crop and Soil Sciences, Michigan State University, 566 PSSB, East Lansing, MI 48824
A combination of cool, wet weather in early spring and planting in reduced-tillage or no-till fields reduces the amount of sulfur released in the soil by decomposition and mineralization of organic matter, particularly in northern regions of the U.S. Recent changes to sulfur emission regulations have decreased the amounts of sulfur that is deposited to the soil through atmospheric channels. Field studies were conducted at six soybean (Glycine max L. Merr) sites in Michigan in 2006 and 2007 to evaluate the effects of sulfur starter fertilizer on nutrient uptake, plant growth, and grain yield. Three sites per year were on-farm strip trials with treatments of ammonium sulfate (21-0-0-24S) band-applied at planting at rates of 0, 5.6, 11.2, and 22.4 kg S ha-1. Other sites each year included additional starter fertilizer treatments of 28 kg N ha-1 and 11.2 kg S ha-1 as gypsum (16% S). In 2006, differences in yield among treatments were significant at only 1 site, where plots receiving the treatment including 11.2 kg S ha-1 yielded 531 kg ha-1 greater than plots receiving 28 kg N ha-1. However, the 11.2 kg S ha-1 treatment did not yield greater than the no-starter control, indicating that the response at this site may have been a negative response to the N-only fertilizer application. Responses observed for plant growth and tissue nutrient concentrations may be attributed to the nitrogen component of the starter source rather than sulfur. When sulfur was applied as gypsum, there were no differences in measured variables compared with the control.