Yield and Quality of Two Cool-Season Grasses as Affected by Selected Herbicides

Abstract

Several herbicides applied either in the fall or spring at rates used for musk thistle (Carduus nutansL.) control had no deleterious effects on two cool-season grasses, smooth brome (Bromus inermisLeyss.) and intermediate wheatgrass [Agropyron intermedium(Host) Beauv.]. Herbicides used were 2,4-D [(2,4-dichlorophenoxy)acetic acid], 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], dicamba (3,6-dichloro-o-anisic acid), picloram (4-amino-3,5,6-trichloropicolinic acid), triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid}, and Dowco 290 (3,6-dichloropicolinic acid). Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] was included for comparative purposes because it is known to affect the protein content of some forage grasses. Effects on the quality of the forages were measured by in vitro dry matter disappearance (IVDMD), protein and KNO3determinations. Intermediate wheatgrass was less susceptible to damage from the highest rates of picloram and atrazine than smooth brome.