Alternative Nitrogen for Subsequent Southern Switchgrass Production Using Cool Season Legumes.

 SEQ CHAPTER \h \r 1Alternative Nitrogen for Subsequent Southern Switchgrass

Production Using Cool Season Legumes

Mitchell B. Holmberg, J. Brett Rushing & Brian S. Baldwin

Dept. of Plant & Soil Sciences, Box 9555

<>Mississippi State University, Mississippi 39762tc "Mississippi State University, Mississippi 39762"

Switchgrass (Panicum virgatum) has become an important biomass crop.   Nitrogen fertilizer can be one of the biggest costs in crop production.  Warm winter temperatures in the Southeast allow for fall establishment and winter growth of cool-season legumes.  These legumes have the potential to provide nitrogen to the spring crop of switchgrass, replacing the need for inorganic nitrogen application.  This study compared biomass production of switchgrass fertilized with five levels of nitrogen (0, 25, 50, 75, and 100 lbs/acre) and seeded to seven legume species: Five clover species; Arrowleaf (Trifolium vesiculosum), ball (T. nigrescens), barrel medic (Medicago truncatula), crimson (T. incarnatum), white clover (T. repens), and two vetch species; common (Vicia sativa L), and hairy (V. villosa R.).  The experiment was a randomized complete block design with four reps super-imposed over an existing switchgrass field.  Yield of the subsequent switchgrass occupying the seeded and fertilized plots indicated a significantly higher yield with 50 lbs of nitrogen compared to 0, 25, 75, and 100 lbs of nitrogen.  Variance around the mean of the grass plot yields caused legume values to separate with both the 50 lbs nitrogen rate and the 0, 25, 75, and 100 lbs nitrogen plots.  The 2011-12 study will add more data to decrease the variance around the means.