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The persistence of preemergence herbicides, butachlor [2-chloro-2,6-diethyl-N(butoxymethyl) acetanilide] and nitrofen(2,4-dichlorophenyl-4-nitrophenyl ether), at 10 ppm level in different soil conditions amended with organic matter and lime was studied under flooded and field moisture capacity. The microbial breakdown played a major role in the dissipation of the herbicides in soil. Nitrofen degradation in flooded soil was greatly accelerated, while it was slowed down in field moisture capacity as compared with butachlor. Increased amendment of rice straw to the soil shortened the half-life of butachlor under flooded condition, however it prolonged that of butachlor when the amendment was exceeded over 1% on dry weight basis. Liming the soil stimulated decomposition of the herbicides in the soil systems, which ap pears to be pH independent.
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