In Field Measurements of Nitrogen Mineralization following Fall Applications of N and the Termination of Winter Cover Crops

Little is known about the timing and quantity of nitrogen (N) mineralization from cover crop residue following cover crop termination. Therefore, the objective of this study was to examine the impact of cover crop species on the return of fall applied N to the soil in the spring following chemical and winter terminations. Fall N was applied (200 kg N ha −1 ) into a living stand of cereal rye, tillage radish, and control (no cover crop). After chemical termination in the spring, soil samples were collected weekly and were analyzed for inorganic N (NO 3 -N and NH 4 -N) to investigate mineralization over time. Cereal rye soil inorganic N concentrations were similar to that of the control in both the spring of 2012 and 2013. Fall N application into tillage radish, cereal rye, and control plots resulted in an average 91, 57, and 66% of the fall N application rate as inorganic N in the spring at the 0-20 cm depth, respectively. The inclusion of cover crops into conventional cropping systems stabilized N at the soil surface and has the potential to improve the efficiency of fall applied N.