Abstract:
Large quantities of herbicides are used on agricultural soils, but the effects of herbicides on the structure
of the soil microbial community have not been well investigated. In this study, soil from three soybean
fields was investigated. The herbicide imazethapyr was applied in one year to soil 1 and in two sequential
years to soil 2. Control soil received no imazethapyr. Microbial biomass and community structure were
characterised using chloroform fumigation–extraction and phospholipid fatty acid (PLFA) determination.
The imazethapyr residue was 1.62 μg·kg−1 in soil 1 and 1.79 μg·kg−1 in soil 2. The microbial biomass
carbon and total PLFAs for soil 2 were much higher than for the other soils. PLFA profiles showed that
fatty acids for Gram-negative and Gram-positive bacteria, as well as total bacteria and total fungi in soil 2
were higher than in other samples. Principal component analysis of the PLFAs showed that the structure of
the microbial community differed substantially among the three different soybean field soils. Application
of the herbicide imazethapyr to soybean fields clearly changed the soil microbial biomass and shifted the
structure of the microbial community
