Atrazine Transport in Irrigated Heavy- and Coarse-Textured Soils, Part II: simulations with the Root Zone Water Quality Model

The hydrological and the pesticide component of the root zone water quality model (RZWQM) were calibrated and evaluated for two different Portuguese soil types: silty loam and sandy soils, under irrigated conditions. The RZWQM is a one-dimensional, process-based model, that simulates the physical, chemical and biological processes in the root zone, and can also accurately simulate macropore flow. The model was calibrated using the 1997 data and tested using 1996 data (soil water content and atrazine concentration in the soil) collected at an Experimental Station located at the Sorraia valley, near Coruche, Portugal, during the summers of 1996 and 1997. Data on plant growth was also available for 1997. The RZWQM is effective in simulating plant growth parameters. For both soil types (silty loam and sandy soils) model predictions on soil water content were in agreement with the observed values. During the calibration year, for most of the irrigation events, model performance was good. Regarding atrazine concentrations, model predictions were in the same range of the observed values. These results indicate that RZWQM can be used, when properly calibrated, to simulate the movement of water and atrazine through the soil profile, for Portuguese conditions.