Effects of Preplant Treatment Interval and Tillages on Herbicide Toxicity to Winter Wheat (Triticum aestivum)

Abstract

Glyphosate plus 2,4-D at 0.3 + 0.5 or 0.4 + 0.7 kg ae ha-1applied 31 to 1 d before seeding did not affect wheat yields or grain test weights, in field experiments in conventionally tilled and no-till winter wheat. In the conventionally-tilled system in each of two years and in the no-till system in a year with 48 mm rain within 7 d before wheat was seeded, picloram applied at 0.14 kg ai ha-1from 31 to 1 d before seeding reduced crop yields by 7 to 8%. In the conventionally-tilled system in a year with only 2 mm rain within 7 d before wheat was seeded, 2,4-D at 3.4 kg ae ha-1and dicamba at 0.14 kg ae ha-1applied 30 to 1 d before seeding, reduced wheat yields by 7 and 4%, respectively. Grain test weights in both tillage systems were increased slightly by picloram at 0.14 kg ha-1, but were decreased slightly by dicamba at 0.14 kg ha-1, in the year with little rain before sowing. Test weights did not differ among herbicides or tillage systems in the year with significant rain a few days before seeding.