Tillage and Sulfur Management for Corn In Fine Textured Soils.

Research to date has not established a consistent, predictable yield response to sulfur for non-sandy or medium-high organic matter soils. Increased use of concentrated fertilizers which contain little or no sulfur, combined with less sulfur from precipitation, have decreased the supply of sulfur to crops. At the same time, higher crop yields have increased the uptake of sulfur from soils. In addition, accumulation of crop residues under minimum tillage systems may reduce plant available sulfur and consequently may lead to increases in sulfur deficiencies and the need for application of sulfur fertilizers. The objective of this research was to evaluate corn yield response to added sulfur to fine textured soils under two rotations and five different tillage practices. This 4-year field experiment was conducted under long-term tillage plots at the Southwest Research and Outreach Center near Lamberton, MN.  Main plot treatments will include: no-tillage, ridge tillage, fall strip tillage, spring disk + field cultivation, and fall moldboard plow. Rotations included corn following corn and corn following soybean. Sulfate fertilizer (subplots) was applied before corn in spring at a rate of 0 or 28 kg S/ha. A combination of soil and plant samples were collected to test whether the crop had sufficient nitrogen and sulfur to attain optimum yield. Yield results were variable from year to year. Significant interaction between sulfur application and tillage system for the corn following corn rotation were observed. Sulfur and tillage treatments significantly affected grain moisture for corn from both rotations but not soybean in the corn following soybean rotation. Ear leaf data showed significant treatment effects due to sulfur and N:S ratio for the corn following corn rotation.