Atrazine and burning in tallgrass prairie infested with prairie threeawn

Abstract

Prairie threeawn (Aristida oligantha Michx.) is an indicator of deteriorated range and is unpalatable and mechanically injurious to livestock. The effects of date of burning (November, February, or April) and atrazine [2-chloro-4-ethylamino)-6+isopropylamino)-5-triazine] applied in March at 0 or 1.12 kg/ha were evaluated in north-central Oklahoma on tallgrass prairie hay meadows infested with prairie threeawn. Atrazine provided consistent control of prairie threeawn and increased yield of desirable species in 2 of the 3 studies. Burning in April reduced prairie threeawn in 1 of 3 studies, but burning in February or November did not reduce prairie threeawn in any of the studies. Combining atrazine and burning controlled prairie threeawn no better than atrazine alone when burning was several months before or after application of atrazine. However, burning just 1 month before application of atrazine decreased the activity of atrazine on prairie threeawn. Burning alone or burning combined with atrazine did not increase production of desirable species.