Broom Snakeweed: Effect on Shortgrass Forage Production and Soil Water Depletion

Abstract

Perennial shortgrasses were delayed in responding to removal of a dense broom snakeweed [Xanthocephalum sarothrae] population (387/m2) because of low initial vigor. After 1 yr, grass production increased by 107% (1175 kg/ha) and after 2 yr, by 324% (2201 kg/ha) compared to undisturbed stands. Reducing snakeweed density by 25 or 50% did not affect forage production during the 2 yr study. Estimated carrying capacity of the shortgrass rangeland was increased from 1 A.U./26 ha to 1 A.U./6.1 ha by the 2nd year after complete removal of broom snakeweed. Juvenile broom snakeweed plants utilized soil water from the upper 15-45 cm. Soil water depletion was increased after perennial grasses regained vigor following complete removal of snakeweeds. Precipitation-use efficiency for production of usable forage was 2.1 and 4.3 times greater on broom snakeweed-free rangeland than on infested rangeland at 1 and 2 yr, respectively, following removal of snakeweed.