Reducing reactive nitrogen (N) loading from farms in the Chesapeake Bay watershed is of paramount concern to residents, farmers, and policy makers. Excess N loading into the Bay from agriculture lead to large anoxic zones. Cover crops can reduce agricultural nutrient loading by increasing on-farm nutrient retention. Greater retention is achieved by reducing soil erosion, increasing water infiltration water holding capacity, and scavenging reactive N after the cash crop has been harvested. Cereal rye (Secale cereale) is typically planted in the fall, and is the most common cover crop in the US. It is characterized by high N-scavenging potential in the fall and slow N-release in the spring. Embedded within a long-term cropping system experiment, we tested the role of a cereal rye cover crop (presence v. absence) and timing of cover crop termination (early v. late) on (1) vertical distribution of N in the soil profile (0-100 cm), (2) temporal dynamics in soil N due to cover crop N release and corn N uptake, and (3) soil moisture movement in the profile effect on N movement.
During the corn growing season, inorganic N pools (to 100 cm) were larger in plots without cover crops than in plots with cover crops suggesting that cover crops can potentially reduce N losses to surface and groundwater. We will use a soil solution model to understand the fate of N throughout the growing season (e.g. corn uptake or potential leaching loss).will also show the effect of reactive N and soil moisture availability on corn N uptake and corn yield. The presence and management of cereal rye is an important tool for mitigating N loss and movement through the soil profile, as well as to maximize grain yield. Our work can be used to improve environmental sustainability of agroecosystems and reduce N losses from the soil profile to protect the Chesapeake Bay.