Effects of Herbicide and Liquid Nitrogen Fertilizer Application on the Establishment of Wheatgrass Pastures in the Texas Rolling Plains

Abstract

Introduced wheatgrasses selected for improved productivity, quality, and drought tolerance may be a complemntary forage to winter wheat and perennial warm-season grasses, filling a gap in spring forage availability in the semi-arid regions of the Texas Rolling Plains. In this experiment, the effects of herbicides applied with water or liquid nitrogen (N) fertilizer on the establishment of crested wheatgrass cv. Hycrest, hybrid wheatgrass cv. NewHy, intermediate wheatgrass cv. Oahe, pubescent wheatgreass cv. Luna and cv. Manska, and tall wheatgrass cv. Jose were investigated. Wheatgrasses were sown at a location near Guthrie, TX in November 1998. Five months after seeding, 2,4-D (2.0 lb ai/A), metsulfuron (Ally; 0.011 lb ai/A), triasulfuron (Amber; 0.026 lb ai/A), dicamba (Banvel; 0.5 lb ai/A), and picloram (Tordon 33K; 0.5 lb ai/A) were applied in an aqueous solution or with liquid N fertilizer carrier (28% N, ammonium nitrate + urea, UAN). One month after herbicide application, plants were evaluated for chlorosis, necrosis, stunting, and stand coverage. Thirty days later, herbage dry matter (DM) yield was determined. Wheatgrasses differed in their responses to individual herbicides; however, the use of sylfonylurea herbicides triasulfuron and metsulfuron, and auxin-type herbicides picloram and dicamba increased or did not affect DM yield when compared to control. Application of UAN in a mixture with these herbicides improved establishment of wheatgrasses compared with herbicides applied in an aqueous solution by reducing leaf and plant injury and increasing DM yield. In contrast, application of the auxin-type herbicide 2,4-D reduced growth of most wheatgrasses when compared to control plants, regardless of the carrier type. When compared to untreated plants, application of auxin-like herbicides resulted in a greater incidence of leaf injury and reduction in DM yield than application of sylfonylurea herbicides.