This Ph.D study presents the development of an integrated nutrient loss model that describes the N and P loss and transport process from soil surface, taking into account environmental degradation. Three series of laboratory experiment were carried out to investigate the physical and chemical mechanisms of the environmental degradation, including the N and P degradation brought forth through natural degradation, infiltration and soil adsorption, and plant up-take. A 17-months field study programme was conducted to calibrate the integrated nutrient loss model. The significance of involving the environmental degradation into the nutrient loss model is evaluated by a comparative study of the full nutrient loss model and the partial model without the temporally variable source term. Published results by others were extracted and reformatted in order to investigated the applicability of the integrated nutrient loss model developed in this study. The findings from the simulation study show that the integrated nutrient loss model could indeed satisfactorily reproduce nutrient loss patterns that closely match the measured nutrient loss by others.