Nitrogen Contribution of Legume Cover Crops in Corn Cropping Systems.

Increases in nitrogen fertilizer costs have prompted many researchers and producers to investigate alternative means of supplying nitrogen to corn. The use of short season legume cover crops is gaining popularity in many areas due to its conservation benefits, but the agronomic benefits are not well understood. The goal of this experiment was to quantify the nitrogen benefit of a legume cover crop (red clover) established after wheat for a subsequent corn crop. Two experimental locations were established in the spring/summer of 2006. At the northern Ohio location, red clover was frost seeded into an established wheat crop in early spring, and at the Western Ohio location, red clover was drilled after wheat harvest. A split-plot in a randomized complete block design was employed with red clover being the main plot effect with 4 replications. Each cover crop stand was terminated in either the fall or the spring (Northwest and Western, respectively). Urea-ammonium nitrate was sidedressed after corn emergence in the spring at nitrogen rates of 0, 90, and 180 kg/ha. Comparison of nitrogen response models for both systems (with and without red clover) revealed that at both locations red clover did affect subsequent corn productivity. The benefit was not however as a result of nitrogen contribution as the optimum nitrogen rates were similar for both systems. Red clover treatments did show a rotational benefit that resulted in increased grain yield. This research reveals that nitrogen contributions from legume cover crops appears to be minimal, but rotational benefits are likely to occur when legume cover crops are established after wheat prior to corn.