Fertilizer Effects on a Winter Cereal Cover Crop.

Benefits associated with conservation tillage in the Southeast are improved by using a winter cereal cover crop. In general, cover crop benefits increase as biomass production is increased, but the infertile soils typically require additional N (inorganic or organic). Currently, limited information exists on optimal rates, sources, and/or time of application to maximize cover crop biomass production. This experiment was located at the Wiregrass Research and Extension Center in Headland, AL on a Fuquay sand (loamy, kaolinitic, thermic Arenic Plinthic Kandiudults) during the 2006-2008 growing seasons. Main plots were time of application (fall and spring), subplots were N source (commercial fertilizer and poultry 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 on an as-sampled basis) for a rye (Secale cereale L.) cover crop. Rye biomass averaged 31% greater in 2008 compared to combined biomass for 2006 and 2007. Commercial fertilizer produced 14% greater biomass compared to poultry litter across all rates and times of application. A Timing x Rate interaction (P = 0.0035) was observed for rye biomass. Fall applications, regardless of source, averaged 22% more biomass compared to spring applications, but the difference was only observed for the two highest rates. A Timing x Source x Rate interaction (P = 0.0135) was also observed for rye biomass. Biomass differences were more pronounced as rates increased with fall fertilizer superior to spring poultry applications. These results provide general information about N fertilizer for biomass production in the Southeast.