Fertilizer Management for a Rye Cover Crop to Enhance Biomass Production

Abstract

Core Ideas Additional N can enhance cereal cover crop biomass production and maximize benefits. Cover crop N fertilizer recovery efficiency averaged 37% across all treatments. Commercial N fertilizer increased biomass for less money compared to poultry litter. Winter cereal cover crops are necessary to achieve maximum benefits of conservation tillage in the southeastern United States. These benefits generally increase as cover crop biomass increases; therefore, we conducted a study to evaluate N application times, sources, and optimal rates to maximize cover crop biomass production at Headland, AL, on a Fuquay sand (loamy, kaolinitic, thermic Arenic Plinthic Kandiudults) during the 2006–2008 growing seasons. Treatments were arranged in a split‐split plot treatment restriction in a randomized complete block design with four replications. Main plots were time of fertilizer application (fall and spring), subplots were N source (commercial fertilizer and poultry [Gallus gallus domesticus] litter), and sub‐subplots were N rate (0, 34, 67, and 101 kg N ha−1 as commercial fertilizer and 0, 2.2, 4.5, and 6.7 Mg ha−1 as poultry litter [as‐sampled basis]) for a cereal rye (Secale cereale L.) cover crop. Commercial fertilizer produced 13% greater biomass compared to poultry litter across all rates and application times. Lower biomass production and higher costs for poultry litter reduced the feasibility of poultry litter as an N source compared with commercial N. Higher C/N ratios were measured for fall‐applied N compared to spring‐applied N, while N fertilizer recovery efficiency (REN) averaged 37% across the experiment. Results indicated fall application of commercial fertilizer N produced superior results across cover crop responses examined in this study, while providing general information about N fertilizer requirements to increase surface residue associated with cover crops across the southeastern United States.