Document Detail

Modeling hydrology, metribuzin degradation and metribuzin transport in macroporous tilled and no-till silt loam soil using RZWQM.
MedLine Citation:
PMID:  15025237     Owner:  NLM     Status:  MEDLINE    
Due to the complex nature of pesticide transport, process-based models can be difficult to use. For example, pesticide transport can be effected by macropore flow, and can be further complicated by sorption, desorption and degradation occurring at different rates in different soil compartments. We have used the Root Zone Water Quality Model (RZWQM) to investigate these phenomena with field data that included two management conditions (till and no-till) and metribuzin concentrations in percolate, runoff and soil. Metribuzin degradation and transport were simulated using three pesticide sorption models available in RZWQM: (a) instantaneous equilibrium-only (EO); (b) equilibrium-kinetic (EK, includes sites with slow desorption and no degradation); (c) equilibrium-bound (EB, includes irreversibly bound sites with relatively slow degradation). Site-specific RZWQM input included water retention curves from four soil depths, saturated hydraulic conductivity from four soil depths and the metribuzin partition coefficient. The calibrated parameters were macropore radius, surface crust saturated hydraulic conductivity, kinetic parameters, irreversible binding parameters and metribuzin half-life. The results indicate that (1) simulated metribuzin persistence was more accurate using the EK (root mean square error, RMSE = 0.03 kg ha(-1)) and EB (RMSE = 0.03 kg ha(-1)) sorption models compared to the EO (RMSE = 0.08 kg ha(-1)) model because of slowing metribuzin degradation rate with time and (2) simulating macropore flow resulted in prediction of metribuzin transport in percolate over the simulation period within a factor of two of that observed using all three pesticide sorption models. Moreover, little difference in simulated daily transport was observed between the three pesticide sorption models, except that the EB model substantially under-predicted metribuzin transport in runoff and percolate >30 days after application when transported concentrations were relatively low. This suggests that when macropore flow and hydrology are accurately simulated, metribuzin transport in the field may be adequately simulated using a relatively simple, equilibrium-only pesticide model.
Robert W Malone; Liwang Ma; R Don Wauchope; Lajpat R Ahuja; Kenneth W Rojas; Qingli Ma; Richard Warner; Matt Byers
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Pest management science     Volume:  60     ISSN:  1526-498X     ISO Abbreviation:  Pest Manag. Sci.     Publication Date:  2004 Mar 
Date Detail:
Created Date:  2004-03-17     Completed Date:  2004-07-20     Revised Date:  2006-04-17    
Medline Journal Info:
Nlm Unique ID:  100898744     Medline TA:  Pest Manag Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  253-66     Citation Subset:  IM    
USDA-Agricultural Research Service, National Soil Tilth Laboratory, 2150 Pammel Dr, Ames, IA 50011, USA.
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MeSH Terms
Agriculture / methods*
Calibration / standards
Models, Biological*
Pesticide Residues / chemistry,  metabolism*
Plant Roots / chemistry,  metabolism
Research Design / standards
Sensitivity and Specificity
Soil / analysis*
Triazines / chemistry,  metabolism*
Water / chemistry,  metabolism*
Reg. No./Substance:
0/Pesticide Residues; 0/Soil; 0/Triazines; 21087-64-9/metribuzin; 7732-18-5/Water

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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