FALL-APPLIED TRIFLURALIN GRANULES IN CONSERVATION-TILL SPRING WHEAT (TRITICUM-AESTIVUM)

Field experiments were conducted to evaluate postplant crop residue, g reen and yellow foxtail control, and wheat grain yield after fall appl ication of trifluralin granules in undisturbed small grain stubble. Le vels of postplant residue were at least 48% cover (line transect metho d) and 2750 kg/ha of aboveground dry matter where herbicide granules w ere left unincorporated or were incorporated with conservation-till me thods, including an undercutter, rotary hoe, or undercutter followed b y a rotary hoe, Trifluralin at 0.56 kg/ha applied as granules in mid O ctober in untilled stubble and incorporated with conservation-till met hods controlled foxtail 81 to 88%, with control appearing slightly low er when granules were not incorporated. The 81 to 88% foxtail control in conservation-till treatments was comparable to control achieved wit h trifluralin at 0.56 kg/ha applied in mid October on conventionally-t illed soil and incorporated by a field cultivator. Foxtail control imp roved somewhat as trifluralin rate was increased to 0.84 and 1.12 kg/h a in conservation-till treatments, Slight wheat stand reductions at 1. 12 kg/ha of trifluralin did not appear to reduce wheat yield. Fall app lication of trifluralin granules in these high-residue conditions appa rently minimizes herbicide losses by photodecomposition and volatility , thereby facilitating good trifluralin efficacy the following season.