By: J. W. Roy, J. C. Hall, G. W. Parkin,* C. Wagner-Riddle, and B. S. Clegg
The leaching of surface-applied herbicides, such as dicamba (2-methoxy-3,6-dichlorobenzoicacid),togroundwaterisanenvironmen-tal concern. Seasonal changes in soil temperature and water content, affecting infiltration and biodegradation, may control leaching. The objectives of this study were to (i) investigate the leaching of dicamba applied to turfgrass, (ii) measure the degradation rate of dicamba in soil and thatch in the laboratory under simulated field conditions, and (iii) test the ability of the model EXPRES (containing LEACHM) to simulate the field transport and degradation processes. Four field lysimeters, packed with sandy loam soil and topped with Kentucky bluegrass (Poapratensis L.) sod, were monitored after receiving three applications (May, September, November) of dicamba. Concentra-tions of dicamba greater than 1 mg L1 were detected in soil water. Although drying of the soil during the summer prevented deep trans-port,greaterleachingoccurredinlateautumnduetoincreasedinfiltra-tion. From the batch experiment, the degradation rate for dicamba in thatch was 5.9 to 8.4 times greater than for soil, with a calculated half-life as low as 5.5 d. Computer modeling indicated that the soil and climatic conditions would influence the effectiveness of greater degradation in thatch for reducing dicamba leaching. In general, EXPRES predictions were similar to observed concentration profiles, though peak dicamba concentrations at the 10-cm depth tended to be higher than predicted in May and November. Differences between predictions and observations are probably a result of minor inaccura-cies in the water-flow simulation and the model’s inability to modify degradation rates with changing climatic conditions.
The leaching of surface-applied herbicides, such as dicamba (2-methoxy-3,6-dichlorobenzoicacid),togroundwaterisanenvironmen-tal concern. Seasonal changes in soil temperature and water content, affecting infiltration and biodegradation, may control leaching. The objectives of this study were to (i) investigate the leaching of dicamba applied to turfgrass, (ii) measure the degradation rate of dicamba in soil and thatch in the laboratory under simulated field conditions, and (iii) test the ability of the model EXPRES (containing LEACHM) to simulate the field transport and degradation processes. Four field lysimeters, packed with sandy loam soil and topped with Kentucky bluegrass (Poapratensis L.) sod, were monitored after receiving three applications (May, September, November) of dicamba. Concentra-tions of dicamba greater than 1 mg L1 were detected in soil water. Although drying of the soil during the summer prevented deep trans-port,greaterleachingoccurredinlateautumnduetoincreasedinfiltra-tion. From the batch experiment, the degradation rate for dicamba in thatch was 5.9 to 8.4 times greater than for soil, with a calculated half-life as low as 5.5 d. Computer modeling indicated that the soil and climatic conditions would influence the effectiveness of greater degradation in thatch for reducing dicamba leaching. In general, EXPRES predictions were similar to observed concentration profiles, though peak dicamba concentrations at the 10-cm depth tended to be higher than predicted in May and November. Differences between predictions and observations are probably a result of minor inaccura-cies in the water-flow simulation and the model’s inability to modify degradation rates with changing climatic conditions.
没有评论:
发表评论