Performance of Annual Medic Species (Medicago spp.) in Southeastern Wyoming

Annual medic (Medicago spp.) pastures that produce high levels of good quality forage are well suited to grazing and are used extensively throughout dryland farming regions of the world. In these regions, they are normally an integral component of cropping rotations because they allow for reductions in weed and disease problems in addition to increasing soil N levels for subsequent crops. The objective of this research was to investigate the performance of 17 annual medic cultivars and experimental lines for their potential use as self-regenerating annual pastures in the dryland cropping region of southeastern Wyoming. Dry matter and seed production capabilities were recorded over three seasons, 1996 to 1998. Growth phase development following different emergence times was evaluated in two seasons, and the forage quality was assessed for medic cultivars and lines grown in the 1997 season. Results revealed that the M. rigidula (L.) All. line, SA10343, consistently produced the greatest level of dry matter, with more than double the amount of forage than nearly all other cultivars. Dry matter production was related to the period of growth and development where higher yielding cultivars showed extended periods of vegetative growth. In general, the southeastern Wyoming climate substantially reduced the growth and development periods of medic cultivars bred in southern Australia. Given the overall performance of all cultivars, it was determined that the M. rigidula species had the greatest potential for further development in this environment.