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Alfalfa (Medicago sativa L.) is an adapted pasture legume for the semi-arid region of western Canada but its use is restricted because of ruminant bloat hazard. Sainfoin (Onobrychis viciifolia Scop.) is a non-bloat-inducing forage legume that yields less forage than alfalfa in this region. Mixture of these legumes may mitigate respective weaknesses by combining their strengths. The objective of this research was to determine the stability of seed-mixture (two legumes seeded in the same row) compared to legume monoculture and alternate row seeding (two legumes seeded in separate but adjacent rows). Three trials were seeded on dryland sites at Swift Current, Saskatchewan, in 1977, 1986, and 1987. Treatments varied from the first trial to the last three but all trials allowed comparison of seed-mixture seeding to monoculture and alternate row swards. In the first and second trials, seed-mixture species composition shifted to alfalfa domination(> 90% alfalfa) over 5 yr more quickly than alternate row, presumably due to interspecific competition. In the other trial, seed-mixture was dominated by alfalfa within 2 yr after seeding due to drought stress. We concluded that sainfoin-alfalfa mixtures are not stable or sustainable in this semi-arid environment.