Lysimeter study of the effect of a vegetative buffer compared to maize and bare soil on the leaching of atrazine and DEA.

Abstract

The efficiency of a vegetative buffer strip to reduce pesticide leaching is poorly understood. Using lysimeters (2m*2m*1m) filled with a silty soil, we compared the effects of rye-grass, maize and bare soil. Leaching was monitored for an application of 250 g/ha of atrazine, which is more than would arrive in run-off. The treatments were compared under irrigations, with equal drainage, equivalent to 350 mm in 5 months, allowing the overall effects of differences in dissipation and preferential transfers on leaching to be estimated. Aerial rye-grass and maize residues were exported, to investigate the effect of root system principally. The results show that under the conditions of this experiment the rye-grass root system enhances the purifying power of the soil and suppressed the leaching of atrazine and partly that of DEA. For the DEA, less adsorbed, a risk of leaching may occur when the pesticide is highly available on the soil surface under the conditions of rapid transfers. The maize had no better purifying effect than bare soil. The effectiveness of rye-grass is attributed to dissipation, due to the large root biomass in the 0-30 cm layer. The value of a grassed strip is greater for weakly adsorbed molecules.