Renovation of Seeded Warm-season Pastures with Atrazine

Abstract

Numerous warm-season pastures have been established in the last 30 years in the central Great Plains. Some of these pastures are old enough to verify that they can be abused by overgrazing as easily as native tallgrass prairies. Overgrazed warm-season pastures are invaded and dominated by cool-season grasses such as smooth brome (Bromus inermis Leyss.) and Kentucky bluegrass (Poa pratensis L.), which diminishes the pasture productivity during the hot summer months. Since established warm-season grasses have greater tolerance to the herbicide atrazine than cool-season grasses, the effectiveness of atrazine applications in renovating invaded warm-season pastures was evaluated. A single, early spring application of atrazine (3.3 kg/ha) killed or sufficiently suppressed the cool-season grasses so that surviving warm-season remnants were able to effectively re-establish the warm-season pasture in a single growing season without any loss in total pasture forage production. Lower rates of atrazine were not as effective, particularly if smooth brome was the primary cool-season grass. The single atrazine application cost was approximately 25% of the seed cost associated with more conventional renovation. Pastures should not be grazed the treatment year but can be hayed at the end of the growing season. The success of the practice is dependent on the presence of warm-season grass remnants. Spraying test strips in small fenced areas would be advisable before treating entire pastures.