The researchers studied how different cover crop management practices affect nitrogen levels in the soil and subsequent corn growth. They compared hairy vetch, rye, and a vetch-rye mixture, finding that hairy vetch accumulated the most nitrogen. The mixture helped conserve nitrogen from the previous year and supplied more nitrogen to the corn than pure rye. Late killing of the cover crops did not significantly impact corn nitrogen uptake. Overall, the vetch-rye mixture acted as a dual-purpose cover crop, balancing nitrogen levels and benefiting corn growth.