Investigating the impact of the manure and trifluralin application rate on herbicide persistence in soil

Widespread use of herbicides throughout the world plays an important role in water and soil pollution. Hence، knowledge of the behavior of herbicides is necessary to reduce their adverse effects on the environment. An experiment was conducted in RCBD with a factorial arrangement of treatments and 3 replications to study the effect of manure and herbicide application rates on trifluralin dissipation in soil. The factors were two amounts of animal manure (0 and 25 ton ha-1) and three application rates of trifluralin (0. 48، 0. 96 and 1. 92 kg ai ha-1). Sampling from the soil was carried out immediately and 7، 14، 28، 48، 90 and 120 days after applying the trifluralin and the herbicide residues were measured using HPLC. Dissipation of trifluralin followed first-order kinetics in the soil and its rate was higher in the amended soil independent of the application doses or cover state. A maximum dissipation rate of 0. 032 mg kg-1 ha-1 was observed in no manure and of 0. 48 and 0. 96 kg ai ha-1 of herbicide; a minimum dissipation rate of 0. 012 mg kg-1 ha-1 was observed in the manure treatment and of 1. 92 kg ai ha-1 for trifluralin. A maximum half-life (57. 75 days) was related to the manure treatment and 1. 92 kg ai ha-1 for trifluralin، and a minimum half-life (21. 38 days) was related to the no manure treatment and 0. 48 kg ai ha-1 for trifluralin. According to the findings of this experiment، the persistence of trifluralin in soil is increased by increasing the application rate of the herbicide and applying manure. It is likely that manure utilization increases trifluralin absorption into the soil which probably results in a reduction in herbicide evaporation.