Multi-Species Cover Crop Effects on Nitrogen Availability in Corn.

Virginia farmers were among the pioneers in no-tillage crop production and the recipe for successful no-till production in the early years always included cover crops.  The reasons for this include soil conservation, nutrient retention, and weed suppression, among others.  Based on past farmer adoption of no-tillage production systems, we know that producers will adopt and maintain systems that noticeably improve soil quality and crop productivity.  In the case of no-till, farmers have experienced the effects of increased soil quality (organic matter) and the concurrent increase in crop productivity.  Adoption of diverse cover crop species mixtures and planting these cover crops in current gaps in crop rotations (e.g., in the typical fallow period after soybean) can result in even further measurable improvements in soil quality.  Understanding the potential nitrogen contribution of multi-species cover crop (MSCC) mixtures to the following corn (Zea mays L.) crop will be essential in order to better integrate mixtures into current cropping systems.  A total of 10 on-farm studies were conducted over two years in the Shenandoah Valley and Northern Piedmont regions of Virginia.  Mixtures of winter-hardy grass and legume cover crops were planted in the fall with aboveground biomass measured in December (fall growth) and at in spring at the time of cover crop termination.  Corn was planted directly into cover crop residue following standard agronomic practices.  At the V6 growth stage corn was sidedress with either 0, 56, or 112 kg N ha^-1.  Corn was harvested with commercial equipment for either grain or silage, depending on site and the effect of N rate determined.  Overall, MSCC contributed up to 80 kg N ha^-1 but the contribution was highly dependent on the timing of spring termination and cover crop biomass.