Choosing the Right Cover Crop Can Reduce Corn’s Nitrogen Needs
A study led by Kritsanee Iamjud, in collaboration with Lisa M. Fultz and Kathleen Bridges, examined how winter cover crops and nitrogen fertilizer rates affect corn production and soil health in a no-till cropping system in northeastern Louisiana.
The researchers compared legume cover crops, a grass–brassica mixture, and winter fallow under four nitrogen fertilizer rates to determine their effects on corn yield, soil nutrient availability, microbial communities, and biological indicators of soil health.
Why It Matters
Cover crops can improve soil health and nutrient cycling, but their effects depend on the species planted. This means growers should not assume that every cover crop will affect nitrogen availability or the following corn crop in the same way.
Understanding these differences can help farmers select cover crops that complement their fertilizer program, improve nitrogen-use efficiency, and maintain crop productivity.
Key Takeaway
Corn following legume cover crops reached maximum yield at a lower nitrogen rate than corn following the grass–brassica mixture. The estimated rate for maximum yield was approximately 90 kg N ha⁻¹ after legumes, compared with 179 kg N ha⁻¹ after the grass–brassica treatment.
Legumes increased soil nitrate and available phosphorus, while the grass–brassica mixture increased soil potassium and influenced different components of the soil microbial community.
For growers, the practical message is clear: cover crop selection should be considered when determining nitrogen fertilizer rates for the following corn crop. Legumes may provide part of the crop’s nitrogen requirement, while grass-based cover crops may retain nitrogen temporarily and require a different fertilizer strategy.
Local soil conditions, cover crop biomass, termination timing, weather, and regional fertilizer recommendations should still guide final nitrogen decisions.
Reference: Iamjud, K., Fultz, L. M., & Bridges, K. (2026). Cover crops and nitrogen rates: Impacts on no-till corn and soil health in Louisiana. Agrosystems, Geosciences & Environment, 9(2), e70378. https://doi.org/10.1002/agg2.70378
