Impacts of 2 commonly used sulfonylurea herbicides and 2 auxin herbicides on establish- ment, inter-specific seedling competition and physiological response under CRP field conditions were evaluated. Seeded species were blue grama [Bouteloua gracilis (Willd). Ex Kunth) Lag. ex Griffiths], sideoats grama [Bouteloua curtipendula (Michx.) Torr.], western wheatgrass [Pascopyrum smith; (Rydb.) A. Love], switchgrass [Panicum virgatum L.], and sand dropseed [Sporobolus cryptandrus (Torr.) Gray].