Trifluralin and ethalfluralin granules in conservation-tillage soybeans (Glycine max)

Abstract

Field experiments were conducted on loam soils in North Dakota to evaluate green and yellow foxtail control and grain yield in soybeans after fall application of trifluralin or ethalfluralin granules in untilled wheat stubble. Herbicides applied in October or November were left unincorporated or were "incorporated" with conservation-tillage methods including an undercutter, rotary hoe, or undercutter followed by a rotary hoe. A conventionally tilled standard treatment was included where trifluralin or ethalfluralin were incorporated by a field cultivator. Levels of postplant residue were at least 52% cover and 3810 kg ha−1 of aboveground dry matter where herbicide granules were left unincorporated or were incorporated by conservation-tillage methods. Trifluralin 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 determined the following June. Control in conservation-tillage treatments was 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 conservation tillage with use of the undercutter. Key words: Conservation tillage, no-tillage, trifluralin, ethalfluralin, rotary hoe, undercutter