Yields of Irrigated Grass and Legume Pasture Mixtures in the Northern Rocky Mountain Area1

Grass‐legume mixtures are of major importance for irrigated pasture in the western United States and provide flexibility in managing other forage resources in an integrated system. I evaluated 20 grass‐legume mixtures for use in the northern Rocky Mountain area. Yield contribution of ‘Regar’ meadow bromegrass ( Bromus biebersteinii Roem and Schult), ‘Manchar’ smooth bromegrass ( Bromus inermus L.), ‘Chinook’ orchardgrass ( Dactylis glomerata L.), and ‘Troy’ Kentucky bluegrass ( Poa pratensis L.) to grass‐legume mixtures was studied when each was seeded in mixtures with alfalfa ( Medicago sativa L.), Ladino clover ( Trifolium repens L.), and birdsfoot trefoil ( Lotus corniculatus L.) or with sainfoin ( Onobrychis viciifolia Scop.) added to each of the latter two. Mixtures were planted in the field into a Bozeman silt loam (Argic‐pachic cryoboroll) soil, grown with adequate irrigation water, and harvested to simulate a frequency similar to that occurring in an irrigated pasture system. Regar meadow bromegrass contributed significantly more to mixture yields than other grasses and alfalfa more than other legumes over the 4‐year period. The two bromegrasses contributed more to yield at the first harvest than orchardgrass or Kentucky bluegrass. Birdsfoot trefoil contributed less than other legumes to mixture yields but sainfoin seeded with birdsfoot trefoil mixtures increased yields to a level equal to that of Ladino clover mixtures. Sainfoin was rapidly lost from mixtures containing Ladino clover. Differences in yield contribution among grasses were least when they were grown with taller‐growing legumes and greatest when grown with shorter‐growing legumes.