Seasonal Leaching and Biodegradation of Dicamba in Turfgrass

• Published in: Journal of environmental quality Vol. 30; no. 4; pp. 1360 - 1370
• Main Authors: Roy, J.W., Hall, J.C., Parkin, G.W., Wagner‐Riddle, C., Clegg, B.S.
• Format: Journal Article
• Language: English
• Published: Madison American Society of Agronomy, Crop Science Society of America, Soil Science Society 01.07.2001; Crop Science Society of America; American Society of Agronomy
• Subjects: Applied sciences; Biodegradation, Environmental; Biological and physicochemical phenomena; Biological and physicochemical properties of pollutants. Interaction in the soil; Climate; Computer Simulation; dicamba; Dicamba - metabolism; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Herbicides - metabolism; Natural water pollution; Poa pratensis; Poaceae; Pollution; Pollution, environment geology; Seasons; Soil and sediments pollution; Soil Pollutants - metabolism; Temperature; Water; Water treatment and pollution; Biodegradation; Auxin; Pollutant behavior; Soil moisture; Pesticides; Runoff water; Soil pollution; Modeling; Herbicide; Transport process; Thatch; Turf; Unsaturated zone; Medium effect; Seasonal variation; Lixiviation; Numerical simulation; Water pollution; Kinetics; Unsaturated soil; Sandy loam soil; Soil temperature
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq2001.3041360x

ABSTRACT The leaching of surface‐applied herbicides, such as dicamba (2‐methoxy‐3,6‐dichlorobenzoic acid), to ground water is an environmental 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 (Poa pratensis L.) sod, were monitored after receiving three applications (May, September, November) of dicamba. Concentrations of dicamba greater than 1 mg L−1 were detected in soil water. Although drying of the soil during the summer prevented deep transport, greater leaching occurred in late autumn due to increased infiltration. 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 inaccuracies in the water‐flow simulation and the model's inability to modify degradation rates with changing climatic conditions.