Spring forage yield and nutritive value of Texas black medic accessions

Black medic (Medicago lupulina L.) has become naturalized in south-central USA where, in semiarid climates, it acts as a cool-season annual. Cultivation for wildlife and livestock forage and seed has not been fully realized as cultivars adapted to warm and dry climates have not been developed. This study evaluated forage yields and nutritive value of black medic accessions collected in Texas. March, April, and May forage yield, acid detergent fiber (ADF), acid detergent lignin (ADL), N, and P concentrations of 11 black medic accessions collected in Texas were compared with cultivar George at Stephenville, TX, during establishment and first self-reseeding years. Entries exhibited no frost damage and insignificant insect damage, but some Texas accessions were more vigorous in February and flowered earlier than other Texas accessions and George. Some Texas accessions were also more productive (P < 0.01) than others as well as George. Forage yields among entries ranged from 0.6 to 1.5 Mg ha(-1) yr(-1) when averaged over years and harvest months. Harvest month affected all entry yields equally and peaked at 2.3 Mg forage ha(-1) yr(-1) during May of the first season but declined in the second, self-reseeding year despite greater rainfall. March ADF, ADL, N, and P concentrations tended to be lower than those of later harvests while the higher-yielding accessions also tended to have greater ADF and ADL concentrations. The results indicate that forage yield and nutritive value of naturalized black medic germplasm from Texas is variable and that a blend from the southern Great Plains should be developed.