Yield Response of Intensively Managed Corn and Soybean to Potassium Fertilizer Rate and Placement

The goal of this project is to examine the variation across a field landscape in corn and soybean yield response to input intensity. The objectives are to identify parts of the landscape most responsive to increased input levels, and to determine the particular constraints to crop growth at these locations during various stages of crop development.

Seven strips of high-input treatments...comparing normal and high rates of potassium (K) across normal and deep placement, and normal and high inputs---nitrogen (N), phosphorus (P), and plant density...were applied in the fall of 2001 across the full length of a large field, in preparation for corn and soybeans. The treatments were repeated for the 2003 and 2004 crops, rotating the corn and soybeans. Starting in the fall of 2004, tillage and fertility treatments were applied only to corn, with soybeans relying on residual fertility.

The intensively managed high potassium treatment has produced corn yields in excess of 220 bu/A in small areas of the landscape, but not much more than 180 bu/A averaged across the field. High inputs boosted corn yields by about 4% in the first two years, increasing to 10% in 2004. Potassium boosted yields equally at grower and high input levels...by about 3% the first 2 years and by 6% in 2004. Potassium reduced corn lodging at high input levels in 2003. The results demonstrate that the impacts of changes in input levels extend well beyond a single year.

Potassium boosted soybean yield by 11% at the grower input level and by 4% at the high input level. Intensive management increased soybean yield by 5%. Up to 2004, soybeans have been grown in twin 30-in. rows, but in the future they will be planted in narrower rows. The project is continuing in 2005. ON-24F