Nitrogen Applications to Increase Cover Crop Biomass and Benefits in the Southeast.

Benefits associated with conservation tillage in the Southeast are improved by using a winter annual cover crop.  In order to maximize associated benefits, biomass production should also be maximized.  For the highly weathered, infertile soils of the Southeast, additional N (inorganic or organic) is typically required; however, no information exists on optimal rates, sources, 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 2006-2008.  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).  Sub-subplot size was 7.3 m wide and 12.2 m long.  Growers that choose to maximize biomass production by utilizing N fertilizer, regardless of source or rate, may benefit more from fall application.  Although not significant, commercial fertilizer tended to promote more cover crop biomass compared to poultry litter, possibly due to ammonia volatilization losses from surface applied poultry litter.  However, no differences were observed between fertilizer and poultry litter rates with the highest rates producing the highest levels of biomass.  Results indicate that poultry litter may be a substitute for costly N fertilizer to promote maximum biomass production in conservation systems.