BY:G. Voos, P.M. Groffman
The objectives of this study were to quantify differences in herbicide persistence in different components of a heterogeneous landscape and to determine if positive relationships between microbial biomass C and N content and herbicide degradation observed in a laboratory microcosm study held up under field conditions. An 80-day field experiment was conducted to study the dissipation of the herbicides 2,4-D and dicamba from soil in a variety of land-use types. The herbicides were applied to 1 m2 plots in corn field, hardwood forest, home lawn and freshwater forested wetland ecosystems. 2,4-D was completely dissipated by Day 20 in each of the land-use types. Dicamba was totally dissipated in the corn and home lawn plots, but was still present on Day 80 in the wetland and hardwood forest soils. In contrast to a previous laboratory microcosm study done with the same soils, at roughly the same time, there were significant negative correlations (p < 0.05) between microbial biomass C and N and soil organic matter content and
dicamba degradation. Dicamba probably persisted in the forest
and wetland soils, which had high microbial biomass, owing to sorption in the
acidic, organic-rich surface horizons of these soils. Our results indicate that
in terrestrial ecosystems, physical soil factors such as sorption can overwhelm
biological factors, including the size of the active microbial biomass, in
determining the environmental fate of these herbicides.
The objectives of this study were to quantify differences in herbicide persistence in different components of a heterogeneous landscape and to determine if positive relationships between microbial biomass C and N content and herbicide degradation observed in a laboratory microcosm study held up under field conditions. An 80-day field experiment was conducted to study the dissipation of the herbicides 2,4-D and dicamba from soil in a variety of land-use types. The herbicides were applied to 1 m2 plots in corn field, hardwood forest, home lawn and freshwater forested wetland ecosystems. 2,4-D was completely dissipated by Day 20 in each of the land-use types. Dicamba was totally dissipated in the corn and home lawn plots, but was still present on Day 80 in the wetland and hardwood forest soils. In contrast to a previous laboratory microcosm study done with the same soils, at roughly the same time, there were significant negative correlations (p < 0.05) between microbial biomass C and N and soil organic matter content and
dicamba degradation. Dicamba probably persisted in the forest
and wetland soils, which had high microbial biomass, owing to sorption in the
acidic, organic-rich surface horizons of these soils. Our results indicate that
in terrestrial ecosystems, physical soil factors such as sorption can overwhelm
biological factors, including the size of the active microbial biomass, in
determining the environmental fate of these herbicides.Yangzhou pioneer chemical CO.,LTD
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