ATRAZINE SOIL METABOLISM IN MAIZE FIELDS TREATED WITH ORGANIC FERTILIZERS

The metabolism of atrazine in soil was studied in two maize fields loc ated in regions with different soil types. Treatments were cow manure or pig slurry (50 tonnes each ha(-1)) applied once either in March or in November before sowing, or green manure incorporated in March. Cont rol plots were not treated with organic fertilizers. Atrazine at 0.75 or 1.0 kg a.i. ha(-1) was applied after sowing. In the 0-12 cm soil la yer, the main atrazine metabolites found were deethylatrazine and hydr oxyatrazine. Low concentrations of deisopropylatrazine and 6-chloro-1, 3,5-triazine-2,4-diamine were also observed. During the 4 months after sowing, the organic fertilizers decreased the rate of atrazine degrad ation, but subsequently there were no differences between treated and control plots. At harvest, the concentrations of atrazine and its meta bolites were very low and similar in all plots. The organic fertilizer s thus did not cause atrazine metabolites to accumulate in soil. In ad dition, atrazine and its metabolites were never detected below 12 cm i n any of the plots.