Recovery of Spring Wheat (Triticum aestivum) Injured by Trifluralin

Abstract

The relationship between trifluralin dosages detected in the soil at seeding, initial crop injury, and subsequent recovery of spring wheat during the growing season was investigated in field experiments in 1986 and 1987. As the amount of trifluralin in the soil increased, both crop density and dry matter production decreased such that at 1 kg/ha the two were reduced by 37 and 50%, respectively, early in the season. As the season progressed, crop growth rates (CGRs) of wheat in trifluralin-treated plots exceeded those of wheat in the untreated plots. Maximum CGRs occurred between Zadok's growth stages 30 and 45 where trifluralin levels in the soil were 0.3 to 0.5 kg ai/ha at seeding. Recovery from trifluralin injury was characterized by enhanced net assimilation rates of surviving plants, increased tillering and greater dry matter production per plant. Wheat seed yield was only weakly correlated with trifluralin levels in the soil at seeding. From a linear regression model it was determined that a 35% reduction in plant dry weight from the trifluralin injury at the beginning of tillering would result in no more than a 10% reduction in seed yield at final harvest.