EFFECT OF PESTICIDES ON MICROBIAL BIOMASS OF FLOODED SOIL

Application of 2,4-D and its analog 2, 4, 5-T at 0.75 mu g g(-1) soil led to a distinct increase in microbial biomass carbon content over th at of untreated soil samples both under flooded and nonflooded conditi ons. 2,4-D was inhibitory to microorganisms at 7.5 and 15.0 mu g g(-1) soil. Repeated applications of a commercial formulation (an isomeric mixture) of hexachlorocyclohexane (HCH) to flooded soil caused a marke d increase in microbial biomass content. Technical grade gamma-HCH was also stimulatory to microbial biomass content. Suspensions of soil tr eated even once with commercial HCH formulation effected rapid aerobic degradation of alpha- and gamma-HCH, but not beta- and delta-HCH, in a mineral salts medium supplemented individually with these isomers as a single carbon source. (C) 1998 Elsevier Science Ltd. All rights res erved.