Effect of Winter Wheat (Triticum aestivum) Straw Mulch Level on Weed Control

Research was conducted to determine the effect of winter wheat (Triticum aestivum L.) straw mulch level on weed control in a winter wheat-ecofallow corn (Zea mays L.)-fallow rotation at North Platte and Sidney, NE, in 1981 and 1982. Wheat straw mulch was established at 0, 1.7, 3.4, 5.1, and 6.8 Mg/ha in stubble fields. After application of 1.5 times the recommended rate at corn planting, metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] concentration remained higher in unmulched soil than in mulched soil for more than 4 months, due to interception of metolachlor by the mulch. Even though the amount of metolachlor in the soil was reduced by mulch, weed control was not reduced and increased with increasing mulch level. Thus, increasing metolachlor rate was not necessary to maintain adequate weed control in no-till winter wheat stubble since mulch itself provided some measure of weed control.