Persistence, production, quality, and steer intake of sainfoin under different defoliation regimes

Sainfoin (Onobrvchis viciaefolia Scop.), a non-bloat-inducing legume, may have potential for steer production on the Southem High Plains. However, sainfoin has exhibited severe persistence problems. The objectives of this experiment were to determine the relationships among intensity of defoliation, plant growth stage, carbohydrate trend, stand productivity and persistence; and to evaluate forage quality trends and estimate steer liveweight gain from sainfoin. The effects of light, medium, and heavy defoliation by clipping or grazing with steers at bud, flower, and seed shatter growth stages on plant persistence, production, carbohydrate trend, and predicted steer production were investigated near Lubbock, Texas, on a Pullman clay loam (fine, mixed, thermic Torretic Paleustoll). The defoliation method did not significantly affect (P > 0.05) stand persistence, harvested yield, or forage quality. Across growth stages the light, medium and heavy use levels averaged 51,70, and 89 % removal of available forage, respectively. Stands declined to 27 and 53 %, respectively, for defoliation at the bud and flower stages under heavy use, but the light and medium use treatments maintained stands above 80 %. The seed shatter treatments at all use levels had increases in stand from self reseeding. Root non-structural carbohydrate concentration decreased in April to a low in June and then increased in late summer and fall, and exhibited no cyclic response to forage defoliation. Sainfoin may be very dependent upon existing photosynthetic tissue to supply energy needs during the summer. A suggested guideline is to remove not more than 70 % of the available biomass. In all growth stages harvested yield was highest, intermediate, and lowest under heavy, medium, and light use, respectively. Harvested yield totals ranged from 11,937 to 4739 kg ha"^ depending on the treatment-use combination. Crude protein averaged 16,14, and 10 % and in YilEQ dry matter digestibility averaged 58, 56, and 45 % at bud, flower, and shatter stages, respectively. Predicted average daily gain ranged from 1.5 on the bud stage under light use treatment to -.3 kg on the shatter stage under heavy use treatment. Predicted beef production ha"^ was highest on the flower stac,- -nder medium use treatment and averaged 868 kg ha"^. This research indicates that with appropriate management, irrigated sainfoin has potential for high steer production and good stand persistence on the Southern High Plains.