Simulation of nitrate leaching for different nitrogen fertilization rates in a region of Valencia (Spain) using a GIS–GLEAMS system

Abstract

Abstract The groundwater loading effects of agricultural management systems (GLEAMS) model coupled to a GIS was used to evaluate the effect of different fertilization treatments on the total N leaching in a selected area of eastern Spain with intensive agriculture. Four nitrogen fertilization rates (traditional or base, base rate reduced by 20%, reduced by 50%, and the rate calculated by the Nmin recommendation system for vegetables, and reduced by 70% for citrus) were evaluated at a regional scale to find the rate that minimized N leaching without reducing crop N uptake. Nitrate leaching maps were obtained for the different nitrogen rates studied. A great reduction of N leaching (up to 68% for vegetables, and 75% for citrus) was observed under the most reduced fertilization rates and this reduction was greater in areas irrigated with surface water in comparison to those irrigated with groundwater. The GIS–GLEAMS system was a useful tool to assess the N leaching at a regional scale for the different N management considered. For example, it was shown that the Nmin recommendation system was the most efficient for vegetables, and for citrus the most efficient fertilization rate was the reduced 50%, that is similar to that recommended by the Code of Good Agricultural Practices. The areas irrigated with groundwater with high nitrate content had a high leaching rate, and the nitrate applied in irrigation water should be considered when planning the crop fertilization. A temporal analysis of the NO3-N in soil, N leaching, crop evapotranspiration and rainfall allowed to identify the influence of the soil NO3-N and the rainfall on nitrate leaching.