An Assessment of Integrated Weed Management Strategies for Purple Threeawn-Dominated Rangelands

Abstract

Purple threeawn (Aristida purpurea Nutt.) is a native bunch grass that is avoided by grazers. It is capable of dominating old cropland and overgrazed pastures, limiting livestock carrying capacity, and degrading wildlife habitat. Traditional management tools have had little impact on threeawn dominance in semiarid regions of the west. Our objectives were to: 1) assess fire and nitrogen treatment effects on threeawn forage quality at various phenological stages to test their potential as pretreatments in a grazing strategy and 2) examine a threeawn-dominated plant community’s response to prescribed fire, nitrogen addition, and clipping. Fire improved threeawn forage quality with greater improvements in early phenological stages. Nitrogen had little effect on forage quality. Fire and nitrogen reduced threeawn while increasing cool season grasses. Light and moderate clipping following fire did not improve the efficacy of fire. Fire appears to an effective preliminary treatment to improve the chance of herbivory.