Integrating Cover Crops for Nitrogen Management in Corn Systems on Northeastern US Dairies

Northeastern U.S. (New York, Pennsylvania, and New England states) dairy farmers are increasingly interested in improving soil health, nutrient sequestration, and dry matter production. Consequently, farmers ask about managing winter cover crops (WCCs) in corn silage (Zea mays L.) rotations. In this literature review we identify WCCs most suitable to the Northeast, and summarize studies on (i) fall and spring N accumulation, (ii) nitrogen fertilizer replacement value (NFRV) for the next corn crop, and (3) environmental and management variables that affect N uptake and NFRV. We also discuss the literature on use of WCCs as forage commodity crops. Overwintering species most suitable for corn silage rotations are wheat (Triticum aestivum L.), cereal rye (Secale cereale L.) and triticale (X Triticosecale Wittm.). Clover (Trifolium spp.) and vetch (Vicia spp.) can add N but require inter-seeding in the Northeast. The NFRV for vetch typically exceeds that of clover, while the NFRVs of winter cereals tend to be low or negative. A few studies suggest cover crop termination with herbicides compared to tillage incorporation can, when no fertilizer N or manure is added, result in slower decomposition and more gradual N release. Research on the effects of tillage on NFRVs of cover crops is inconclusive. When seeded aft er corn silage, cereal rye is most effective in N uptake in fall and spring. A corn rotation that includes cereal rye or triticale that can be harvested has the potential to reduce soil erosion, capture residual N, increase annual forage yields, and provide quality forage.