Field evaluation of a multicomponent solute transport model in soils irrigated with saline waters

Soil salinization, sodification, and non-point source pollution are among the most important and widespread environmental problems in agricultural regions with scarce water resources. Models evaluating these environmental problems should therefore consider an integrated approach to avoid favoring one problem over the other. The HYDRUS-1D software package was used to simulate water movement and solute transport in two complex experiments carried out under field conditions in Alvalade and Mitra, Portugal. The experiments involved irrigating maize with synthetic saline irrigation waters blended with fresh irrigation waters and waters with different nitrogen concentrations. The major ion chemistry module of HYDRUS-1D was used to model water contents (RMSE <= 0.04 cm(3) cm(-3)), the overall salinity given by the electrical conductivity of the soil solution (ECSW) (RMSE <= 2.35 dS m(-1)), the concentration of soluble cations Na+ (RMSE <= 13.86 mmol((c)) L-1), Ca2+ (RMSE <= 5.66 mmol((c)) L-1), Mg2+ (RMSE <= 4.16 mmol((c)) L-1), and SAR (RMSE <= 6.27 (mmol((c)) L-1)(0.5)) in different experimental plots. RMSE were always lower for the soil with coarse texture of Mitra. The standard HYDRUS solute transport module was used to model N-NH4+ (RMSE <= 0.07 mmol((c)) L-1) and N-NO3- (RMSE <= 2.60 mmol((c)) L-1) concentrations in the soil solution while either including or neglecting the effects of the osmotic stress on nutrient uptake. The model was able to successfully simulate root water and nutrient uptake reductions due to osmotic stress. Consequently, modeled fluxes of N-NH4+ and N-NO3- leached from the soil profiles increased due to the effects of the salinity stress on water and nutrient uptake. Possible causes of disagreements between the modeling and experimental data are discussed. HYDRUS-1D proved to be a powerful tool for analyzing solute concentrations related to overall soil salinity and nitrogen species. (C) 2011 Elsevier B.V. All rights reserved.