Microbial degradation of benthiocarb, MCPA and 2,4-d herbicides in perfused soils amended with organic matter and chemical fertilizers

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Abstract
The degradation of benthiocarb, MCPA and 2,4-D in soils amended with rice straw, compost and chemical fertilizers was studied using the soil perfusion technique. In the control (non-amendment) and rice straw treatments, rapid degradation of benthiocarb occurred after a lag period of 12 days. On the other hand, compost and N-P-K amendments, especially the latter, shortened the lag period. Single applications of N, PorK did not affect the benthiocarb degradation so much as the combined application of these materials, except that N appeared to promote the degradation by shortening the lag period. The courses of degradation of MCPA and 2,4-D appeared to show two stages of lag period. In MCPA degradation, the amendments of organic materials or N, P, K fertilizers did not affect the first lag period but strongly affected the second lag period. In 2,4-D degradation, however, the initial lag period was affected by the various amendments, in contrast to that of MCPA degradation. The promotive effect of P was more remarkable than that of Nor K for both 2,4-D and MCPA. The degradation rates of the herbicides were influenced by the amounts of P or organic materials applied to the soil.