Long-term simulation of some soil chemical properties under continuous wheat cultivation irrigated with waters of different qualities

Abstract

The use of low-quality waters for irrigation in arid and semiarid regions is increasing due to the shortage of good-quality water supplies. Geochemical simulations are cost-effective ways to determine the suitable strategies for sustainable water and soil management. In the first step of this study, the combination of one-dimensional solute transport equation and cation exchange model in PHREEQC was used to predict breakthrough curves of the exchangeable sodium percentage (ESP) of nine soil columns during the leaching with 20 pore volumes of a solution with sodium adsorption ratio (SAR) of 10. In the second step, the trend of changes in solution and exchangeable phases of a non-sodic agricultural soil was simulated over 20 years of continuous wheat cultivation irrigated with waters of different qualities. The graphical and statistical comparison (RMSE values ranged from 0.36 to 0.95) between experimental and predicted results showed that the geochemical simulations in the first step were successful. Simulation results of the second step indicated that the soil ESP decreased from 10.1 to 5.6% after a 20-year consecutive application of water with SAR 2.5, while the long-term use of irrigation waters with SAR 10 and SAR 40 increased the final soil ESP to 27.8 and 88.5%, respectively. In the case of application of irrigation water with SAR 10, the final ESP values of wheat residues-, gypsum-, and calcite-amended soils were 18.5, 16.9, and 20.2% which were less than that obtained for control soil.