Crop Residues and Management of Annual Grass Weeds in Continuous No-Till Wheat (Triticum aestivum)

Abstract

Field and growth chamber experiments were conducted from 1983 to 1985 to determine the relationships between loss in plant productivity and plant residue-crop-weed density in no-till wheat (Triticum aestivumL.) and to document chemical management and cultivar options for such a cropping system. Untilled stubble left on the soil at rates of 0.5 and 3 t/ha reduced wheat density and grain yield in continuous winter wheat. Stem densities of cheat (Bromus secalinusL. # BROSE) and downy brome (B. tectorumL. # BROTE) in mulched treatments averaged about 682, 679, and 38 stems/m2in 1983, 1984, and 1985, respectively. In the nonmulched treatment, weed density and standing dry matter ranged from 5 to 30 stems/m2and 2 to 6 g/m2, respectively. Removal of residues eliminated key habitat characteristics required for the establishment ofBromusspp. Preemergence and early postemergence applications of BAY SMY 1500 [4-amino-6-(1,1-dimethylethyl)-3-(ethylthio)-1,2,4-triazin-5(4H)-one] at 2 kg/ha controlled both species ofBromusin no-till wheat. The herbicide treatment slightly delayed maturity of 10 wheat cultivars, but control of cheat and downy brome allowed nine cultivars to attain their yield potential, improving grain yield over that of untreated plots. ‘Vona’ wheat did not tolerate the herbicide and was susceptible after emergence. BAY SMY 1500 widens the spectrum of weed management and wheat cultivar options for an annual conservation production system of winter wheat.