Field Evaluation of a Multicomponent Solute Transport Model in Soils Irrigated with Saline Waters.

Soil salinization/sodification and non-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. The experiments involved irrigating maize with waters of different salinities and nitrogen concentrations. The major ion chemistry module of HYDRUS-1D was used to successfully model water contents, the overall salinity given by the electrical conductivity of the soil solution (EC_sw), the concentration of soluble cations Na⁺, Ca²⁺ and Mg²⁺, and SAR in different experimental plots. The agreement between observed and simulated values was best for EC_sw and soluble Na⁺. The other parameters were predicted slightly less well, failing in some of the goodness-of-fit tests due to limitations inherent in the field experiments rather than the model ability. The standard HYDRUS solute transport module was used to model N-NH₄⁺ and N-NO₃^- concentrations in the soil solution while either assuming 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. HYDRUS-1D proved to be a powerful and useful tool for analyzing concentrations of components related to overall soil salinity and nitrogen species.