Clover Cover Crops and Nitrogen

In PA we have done a few experiments on this. Several years ago research in northeastern PA showed that we got 80–144 lb N/A from red clover established in wheat or oats. In more recent research in central PA, we found 62–110 lb N/A from red clover established in wheat. In a similar experiment at Landisville in 2008, the N contribution from the red clover was only 40 lb N/A. However, at this location, the corn following the clover cover crop actually required more N to achieve the maximum economic yield than the corn with no cover crop. Interestingly, this was because the maximum yield following the red clover cover crop here was 30 bu/A higher than the maximum yield with no clover. Also, in 2007 at the Centre County location, the yield following the clover cover crop was 17 bu/A higher than with no cover crop. This represents a very significant non-N contribution from the cover crop which further increases the value of the cover crop.

Based on this summary of research and our more limited experience in PA we can probably reliably count on 80–100 lb of fertilizer equivalent N from a good stand of red clover cover before corn. The stand and growth definitely makes a difference in the amount of N available. Therefore, adjust these credits down for poor stands or poor growth before termination. Thus for an investment of around $25/A for seed and planting, we can get around $40 worth of N, plus the non-N yield benefits from the red clover cover crop. Some farmers are also harvesting one cutting of hay from this clover which adds an additional value but the N contribution will be reduced around 30 lb/A if the hay is harvested. Realize that this research reflects a significant range in the benefits and costs but it does give us some ball park figures to use in our crop planning.

By Doug Beegle, Distinguished Professor of Agronomy

Article orginally published in PSU Field Crop News Volume 10:6.