Cover Crop Decomposition and Residue Nitrogen Release Dynamics.

Nitrogen (N) loss from agriculture fields in the Corn Belt contributes to impaired waterways and the development of the “Dead Zone” in the Gulf of Mexico. It has been well established that cover crops have the ability to scavenge N, which results in a reduction of N loss via tile drainage. However, the release of cover crop residue N is not well understood in the Corn Belt region. Therefore, the goal of this project was to better understand cover crop residue N release and the synchrony of that release with cash crop N demands within the Corn Belt. To achieve this goal, a litter bag study was established at the Purdue Agronomy Center for Research and Education (ACRE). Treatments considered in this study were crop rotation: Corn/Soybean, Soybean/Corn, and Continuous Corn; cover crop species: hairy vetch (Vicia villosa Roth) and cereal rye (Secale cereal); tillage: No-till and reduced tillage. Tillage and cover crop species significantly influenced the rate of cover crop decomposition and N release. On average, tillage increased the rate of decomposition and N release from cover crop residue by 24% for both cereal rye and hairy vetch. Hairy vetch treatments released an average 73% (No-till) and 92% (reduced till) of their initial N concentrations by the end of June. Compared to cereal rye treatments which released 61% (No-till) and 78% (reduced till) by the same date. The data also revealed that greater than 50% of N release occurred for all treatments by mid-June. This suggests that the majority of cover crop N release would synchronize with the point when corn has its greatest rate of N uptake (V5-V12). Thus, indicating the potential of cover crop residue N to be utilized by the following cash crop.