TRIFLURALIN AND ETHALFLURALIN GRANULES IN CONSERVATION-TILLAGE SOYBEANS (GLYCINE-MAX)

Field experiments were conducted on loam soils in North Dakota to eval uate green and yellow foxtail control and grain yield in soybeans afte r fall application of trifluralin or ethalfluralin granules in untille d wheat stubble. Herbicides applied in October or November were left u nincorporated or were ''incorporated'' with conservation-tillage metho ds including an undercutter, rotary hoe, or undercutter followed by a rotary hoe. A conventionally tilled standard treatment was included wh ere trifluralin or ethalfluralin were incorporated by a field cultivat or. Levels of postplant residue were at least 52% cover and 3810 kg ha (-1) of aboveground dry matter where herbicide granules were left unin corporated or were incorporated by conservation-tillage methods. Trifl uralin and ethalfluralin at 1.12 kg ha(-1) applied as granules in mid- October in untilled stubble and incorporated with conservation-tillage methods controlled foxtail 88-92% and 87-94%, respectively, as determ ined the following June. Control in conservation-tillage treatments wi ts as effective as the conventional tillage standard of trifluralin or ethalfluralin at 1.12 kg ha(-1). Soybean yield correlated reasonably well with foxtail control and appeared to be maximized where good weed control was achieved either in conventional tillage or in conservatio n tillage with use of the undercutter.