Kill Date of Vetch, Rye, and a Vetch–Rye Mixture: I. Cover Crop and Corn Nitrogen

Abstract Spring kill date affects cover crop N content and N availability to subsequent no‐till corn ( Zea mays L.). This 2‐yr study was conducted in 1990 and 1991 at Coastal Plain and Piedmont locations in Maryland to evaluate three cover crop kill dates, three corn planting dates, and four corn fertilizer N (FN) rates following hairy vetch ( Vicia villosa Roth), cereal rye ( Secale cereale L.) and a vetch‐rye mixture. No‐cover checks were included for each corn planting date. Fertilizer N rates were 0 to 202 kg ha −1 in the Piedmont and 0 to 270 kg ha −1 for the Coastal Plain. The vetch‐rye mixture contained as much or more N than vetch, and more N than rye within each kill date. Cover crop biomass and N content increased for each delay in kill. In a 50‐d period from late March until early May, vetch and the vetch‐rye mixture accumulated about 2 kg N ha −1 d −1 , with total topgrowth N accumulation from 144 to 203 kg ha −1 over two locations and two years. Greatest rye N accumulation was 51 kg ha −1 . Corn N content ranged from 37 to 293 kg ha −1 , and was significantly affected by FN rate. Within FN rate, N content was greater following vetch or vetch‐rye than following rye or no cover, particularly at low FN rates. Corn N content was greater if cover kill and corn planting were delayed until late April or mid‐May. This was attributed to greater cover crop N production and mulching effects, and the timing of summer rainfall. Corn FN requirements were greatest following rye or no cover, intermediate following vetch‐rye, and least following vetch. This demonstrates that cover crop species and kill date can be managed to conserve N with rye, supply N for the next crop with vetch, or provide both N conservation and N supply with a vetch‐rye mixture.