[Effects of pesticide-contamination on population size and denitrification activity of denitrifying bacteria in paddy soils].

The effects of pesticide contamination on the population size and denitrification activity of denitrifying bacteria (DNB) were studied with three types of paddy soil (Huangsong paddy soil, red earth paddy soil and purple paddy soil) treated with carbofuran, carbendazim and butachlor for four weeks. The results showed that the population size of DNB in purple paddy soil, Huangsong paddy soil and red earth paddy soil varied in the range of 59.04 x 10(4)-157.59 x 10(4), 42.89 x 10(4)-108.97 x 10(4) and 32.14 x 10(4)-75.30 x 10(4) cfu.g-1 dried soil, respectively, which was positively related to the quantity of consumed nitrate in paddy soils. The population size and denitrification activity of DNB were increased by adding carbofuran (1 mg.kg-1 dried soil) or butachlor (1 mg.kg-1 dried soil), but decreased significantly by adding 10 mg.kg-1 dried soil of butachlor, 5 mg.kg-1 dried soil of carbofuran, and 10 mg.kg-1 dried soil of carbendazim on 7th d, 14th d and 7th d, respectively.