Performance of Irrigated Tall Fescue–Legume Communities under Two Grazing Frequencies in the Southern Rocky Mountains, USA

Abstract

Irrigated pastures form a significant component of agriculture in the irrigated steppe of the southern Rocky Mountains, USA. Information is limited, however, describing performance of grazed binary perennial cool‐season grass–legume mixtures in the region. Established monoculture tall fescue [Festuca arundinacea Schreb. = Lolium arundinaceum (Schreb.) S.J. Darbyshire] + 134 kg N ha−1 (MONO) and tall fescue mixed with alfalfa (Medicago sativa L.) (ALF/TF), birdsfoot trefoil (Lotus corniculatus L.) (BFT/TF), cicer milkvetch (Astragalus cicer L.) (CM/TF), or kura clover (Trifolium ambiguum M.B.) (KC/TF) at New Mexico State University's Sustainable Agriculture Science Center at Alcalde were subjected to two grazing frequencies (grazed monthly or bimonthly mid‐May to mid‐September) from 1998 to 2000. Grass, legume, and combined dry matter (DM) yields were measured in May 1998 to 2001. A year × grazing frequency × pasture interaction for legume DM yield was moderated by a lack of effect in grass DM yield, leaving a year × pasture interaction for combined DM yield in which MONO, ALF/TF, and CM/TF increased linearly across years and cubic trends were exhibited by ALF/TF and KC/TF. Despite the cubic trend of KC/TF, it and BFT/TF had the most uniform yield distribution across years because of nonsignificant linear effects. Annual combined DM yield averaged 2.21, 3.90, 2.43, 1.93, and 3.03 Mg ha−1 for MONO, ALF/TF, BFT/TF, CM/TF, and KC/TF, respectively, from 1998 to 2001 (5% LSD = 0.77). Kura clover‐tall fescue offers an alternative to alfalfa– tall fescue for long‐term pastures in the irrigated steppe of the southern Rocky Mountains.