Barley grass control with herbicides in subterranean clover pasture. 1. Effect on pasture in the year of spraying

Abstract

Barley grass (Hordeum spp.) in a subterranean clover pasture was controlled with herbicides in the time between the 2-3 leaf stage and flowering. The effects on subsequent pasture production and composition were measured and the interaction between grazing and herbicides was also assessed. Early removal of barley grass reduced dry matter production in winter by an average of 41%. It also allowed an incursion of Indian hedge mustard (Sisymbrium orientale L.). which was suppressed by grazing but comprised an average of 23% ground cover in ungrazed pasture. Loss of total pasture production decreased as the date of herbicide application was delayed from June to September. Broadleaf species compensated for the early removal of barley grass, so that total dry matter production in spring in herbicide-treated areas was higher than in the unsprayed pasture. Fluazifop-p at 32, 53, and 106 g a.i/ha gave, respectively, 94, 91, and 94% reduction in barley grass seedhead density when applied at the 2-3 leaf stage, and 64, 88, and 98% reduction when applied at mid jointing. Application of this herbicide at 53 or 106 g a.i/ha for barley grass control can be delayed until late winter, thereby maintaining winter feed production but avoiding declining palatability and awned barley grass seeds.