EFFECTS OF 3 HERBICIDES ON SOIL MICROBIAL BIOMASS AND ACTIVITY

Three post-emergence herbicides (2,4-D, picloram and glyphosate) were applied to samples of an Alberta agricultural soil at concentrations of 0, 2, 20, and 200 μg g-1. The effects of these chemicals on certain microbial variables was monitored over 27 days. All herbicides caused enhancement of basal respiration but only for 9 days following application, and only for concentrations of 200 μg g-1. Substrate-induced respiration was temporarily depressed by 200 μg g-1 picloram and 2,4-D, and briefly enhanced by 200 μg g-1 glyphosate. It is concluded that because changes in microbial variables only occurred at herbicide concentrations of much higher than that which occurs following field application, the side-effects of these chemicals is probably of little ecological significance. © 1990 Kluwer Academic Publishers.