Forage production of sainfoin across an irrigation gradient

Limited water and curtailed use of public lands for grazing has increased interest in intensively managed pastures in the western USA. Our objective was to evaluate forage production of sainfoin (Onobrychis viciifolia Scop.), a nonbloating legume, compared with alfalfa (Medicago sativa L.). Thirteen sainfoin cultivars and 'Deseret' alfalfa were evaluated at four water levels (WLs) and four harvests in 1998 and 1999 under a line-source irrigation system. Water levels (WL1, WL2, WL3, and WL4) received an average of 78.3, 65.8, 34.9, and 8.3 cm of water, respectively. Significant effects were found for cultivar, cultivar x WL, harvest date, and cultivar x harvest date. Annual production of sainfoin at WL1, WL2, WL3, and WL4 was 11.6, 11.4, 9.6, and 8.9 Mg ha(-1), respectively, whereas annual production of Deseret was 20.7, 18.5, 18.0, and 16.3 Mg ha(-1), respectively, Overall yield trends across WLs were linear for sainfoin and Deseret and were parallel (P = 0.55) with slopes of b = 0.042 and b = 0.054, respectively. Yield of sainfoin at Harvest 1 through 4 was 5.5, 2.1, 1.5, and 1.3 Mg ha(-1), respectively. Yield of Deseret from Harvest 1 through 4 was 5.9, 5.3, 4.7, and 2.4 Mg ha(-1), respectively. Yields of the two species at Harvest 1 did not differ. The flat linear trend across WLs verifies that both crops are tolerant to dry conditions. With its highest production potential during early growth, sainfoin is best suited for situations where early growth of a nonbloating legume is desired, but will not compete with alfalfa in total seasonal production.