LAUSR

ABSTRACT Information is limited on using winter legumes as a source of nitrogen (N) intercropped with switchgrass in the southern Great Plains of the United States. The objectives of this study were to evaluate N contribution of several winter legumes to switchgrass, and to determine the influence of winter legumes on biofuel quality and soil fertility status. Field experiments were conducted at two locations in Oklahoma in which six winter legumes and four rates of N fertilizer were studied over a 3-year period. Winter legumes did not increase switchgrass forage yield, cellulose, lignin, and hemicellulose concentrations at any location. Soil organic matter (OM), nitrate-N (NO3-N), soil test phosphorus (P), soil test potassium (K), and soil pH remained unchanged. In contrast, applying inorganic N only increased switchgrass yield. This study demonstrated that southern Great Plains may not be conducive to utilizing legumes as the primary N source for switchgrass.