Effect of grasses on herbicide fate in the soil column: infiltration of runoff, movement, and degradation.

摘要

The objective of the present study was to evaluate if the presence of grass or the type of grass influences the environmental fate of herbicides within a soil column. Intact soil columns were planted with either smooth brome, big bluestem, tall fescue, switchgrass, or a mixture of prairie grasses or were left unvegetated. Artificial runoff containing atrazine, metolachlor, and pendimethalin was applied to the columns and allowed to infiltrate, and the resulting leachate was collected at the bottom of the soil column. This process was repeated on day 7 with herbicide-fortified runoff and on days 14 and 21 with water only. Following the leaching experiments, soil from the columns was fortified with either [14C]atrazine or [14C]metolachlor to measure pesticide degradation potential. The mean time necessary for infiltration of the artificial runoff decreased from 7.5 h for unvegetated to 3.4 h for grassed soil columns, and the type of grass did not have a significant effect. Neither the type of grass nor the presence of grass caused a significant change in the total amount of herbicide that leached through the columns. However, the presence of some grasses did decrease the amount of herbicide that leached in the final two events (i.e., additions not fortified with herbicide). Fescue was the least effective, reducing the amount of leached atrazine and metolachlor by 13% and 33% respectively, and mixed prairie grass was most effective, with reductions of 43% and 44%, respectively. In addition, atrazine and metolachlor degraded more rapidly in soil vegetated by some grasses. Mixed prairie grass had the greatest effect, increasing atrazine mineralization by 260% and formation of metolachlor-bound residue by 760%.