This research was aimed at studying the leaching of diuron in soil columns, as well as the effect of different methods of reduction of microbial activity on diuron degradation in samples of a sandy loam soil (LVd) and a clay soil (LRd). To measure the downward movement of diuron (0; 1.6 and 3.2 kg ha-1), water layers of 0, 20 40, 60 and 80 mm were applied. For degradation studies, the methods used to restrict were as follow: sterilized in autoclave, methyl bromide application, amoxicillin, captan and amoxicilin+captan; soil samples were kept with or without light incidence. Water depths > 60 mm were enough to promote observable leaching in LVd samples. For clay soil, regardless of the water layer applied, herbicide movement was limited to the superficial soil layer. In degradation studies, biomass accumulation of bioindicator Brachiaria decumbens was higher in LRd samples with no restriction. LVd soil samples treated with any microbial activity restriction methods and exposed to light led to bioindicator biomass reduction, in comparison to others treatments. For both soils, biomass of B. decumbens was increased in soil samples that remained exposed to light.
residual effect; mobility; persistence; retention
