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Title:   Author  item
                                            Malone, Robert

                                                         - *Rob*item
                                            Ahuja, Lajpatitem
                                            Ma, Liwangitem
                                            Wauchope, Robert

                                                         - *Don*item
                                            Rojas, Kennethitem
                                            MA, QINGLI - ENVIRON. & TURF SERVICES
  Submitted to: Pest Management Science
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 7/31/2003
                                    Publication  Date: 5/7/2004
                                    Citation: Malone, R.W., Ahuja, L.R., Ma, L., Wauchope, R.D., Rojas, K.W., Ma, Q. 2004. A review of the root zone water quality model (RZWQM). Pest Management Science. 60:205-221.Interpretive Summary: Pesticide transport models offer cost-effective methods to investigate pesticide management strategies, to study pesticide processes under different conditions, and to help illuminate which aspects of a system are most in need of further lab or field study.  The root zone water quality model (RZQWM) is an agricultural systems model being used to  study the effects of agricultural management, including pesticide management, on environmental quality.  This paper reviews RZQWM history, the distinguishing features and components of the model, and results of studies to validate the model.  Results of this review conclude that processes affecting pesticide transport can be adequately simulated by RZQWM.  These processes include evapotranspiration, soil water movement, water percolation and runoff, plant growth, and pesticide degradation and sorption.  This review will impact RQWM users and developers by helping  identify the strengths and weaknesses of the model as well as defining successful modeling strategies.
                                Technical Abstract: Pesticide transport models are tools used to develop improved pesticide management strategies, study pesticide processes under different conditions (management, soils, climates, etc.), and illuminate aspects of a system in need of more field or lab study.  The Root Zone Water Quality Model (RZWQM) simulates pesticide transport under different conditions,  but to simulate pesticide transport some understanding of the whole model is necessary (e.g., plant growth, hydrology).  Therefore, this paper briefly overviews RZWQM history and distinguishing features, overviews key RZWQM components, and reviews RZWQM validation studies.  The RZWQM is a physically-based agricultural systems model that includes sub-models to simulate infiltration, runoff, water distribution, and chemical movement in the soil; macropore flow and chemical movement through macropores; evapotranspiration (ET); heat transport; plant growth; organic matter/N  cycling; pesticide processes; chemical transfer to runoff; and the effect of agricultural management practices on these processes.  Research to date shows that if key input parameters are calibrated, RZWQM can adequately simulate the processes involved with pesticide transport (ET, soil water content, percolation and runoff, plant growth, and pesticide fate).  A review of the validation studies revealed that accurate parameterization of restricting soil layers (low permeability horizons) may improve simulated soil water content; simulating pesticide sorption kinetics may improve simulated soil pesticide concentration by depth; and calibrating the pesticide half-life may improve simulated pesticide persistence.


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