The researchers studied how different kill dates for cover crops like vetch and rye affect the nitrogen content and availability for corn crops. They found that delaying the kill date of cover crops led to increased nitrogen content. Vetch and vetch-rye mixtures accumulated more nitrogen than rye. Corn planted after vetch or vetch-rye had higher nitrogen content compared to corn planted after rye or no cover crop. Delaying the kill date of cover crops and corn planting until late April or mid-May resulted in higher nitrogen content in corn. Overall, the study shows that managing cover crop species and kill dates can help conserve nitrogen with rye, supply nitrogen for the next crop with vetch, or provide both nitrogen conservation and supply with a vetch-rye mixture.