<i>Global sensitivity analysis of RZWQM2-P in simulation of agricultural phosphorus loss</i>

Abstract

Abstract. In assessing how the output of a numerical model is influenced by its input parameters, sensitivity analysis provides a guideline in identifying and selecting key parameters while calibrating the model. Recently developed RZWQM2-P model, integrating a new phosphorus (P) module into the RZWQM2 model, was shown to successfully simulate P losses through surface runoff and tile drainage under different agricultural management practices. No global sensitivity analysis was performed for the newly developed RZWQM2-P model‘s simulation of P losses, leaving key parameters governing P losses simulation unidentified. The present study‘s objective was to address this shortcoming. Morris screening and Sobol-variance-based sensitivity analysis methods were applied to the prediction of dissolved reactive P (DRP) and particulate P (PP) losses through surface runoff and tile drainage. Data were collected from a liquid cattle manure applied experimental field with maize and soybean rotation in Ontario, Canada. Macroporosity proved to be a sensitive parameter in simulating P losses in all forms and from all outlets, while DRP loss through surface runoff was most sensitive to the P extraction coefficient, and PP loss through surface runoff was mainly governed by Universal Soil Loss Equation (USLE) parameters. Tile flow DRP and PP losses were most sensitive to the plant P uptake distribution parameter and the soil detachability coefficient, respectively. These results will inform the development of guidelines for RZWQM2-P model calibration.