Finding Legumes for the Texas High Plains.

Inclusion of legumes in pastures is becoming more important as N prices escalate but legumes require more water for growth than warm-season grasses. In semi-arid regions where water is scarce, finding appropriate legumes is challenging. In west Texas, alfalfa (Medicago sativa L.), yellow sweetclover (Melilotus officinalis Lam.) and sainfoin (Onobrychis viciifolia Scop.) were each interseeded into three old world bluestems including ‘WW-B. Dahl’ [Bothriochloa bladhii (Retz)], ‘WW Sparr’ [Bothriochloa ischaemum (L.) Keng. var. ischaemum (Hack.)], and ‘Caucasian’ [Bothriochloa caucasica (Trin.)]. Additionally, no N and 60 kg N ha-1 treatments were included. Treatments were replicated three times in a randomized block design with a split-plot treatment arrangement. Forage mass (kg ha-1) and concentrations of N in both the grass and the legume components were determined in June, July, and October. Total irrigation water applied through subsurface drip was limited to a maximum of 250 mm, annually. Nitrogen fertilizer increased grass biomass in Sparr and Caucasian in June and July but not in October, compared with no N. The N response in Dahl occurred by July and remained in October. Inclusion of legumes increased total biomass in all three grasses in June and July, compared with the mean of no legumes but was only observed in Dahl in October. Legumes increased crude protein in the associated Sparr and Dahl compared with no legumes but had no effect on Caucasian. Responses due to inclusion of legumes were largely due to inclusion of yellow sweet clover. This legume appears to have potential for increasing yield and crude protein in old world bluestems in west Texas with limited irrigation.