Simulation of Water and Salt Transport in Soil Using the HYDRUS-1D Software

In this study the HYDRUS-1D software has been applied to simulate water and salt transport through the soil profiles. Field experiments were performed as a randomized complete blocks design in Zabol University campus. Four leaching treatments with five replications were conducted within the blocks. The treatments included 10 irrigations with 100 mm water every 3 days (T1), 7 irrigations with 150 mm water every 7 days (T2), 5 irrigations with 200 mm water every 6 days (T3) and 4 irrigations with 250 mm water every 4 days (T4). For each treatment, soil samples were taken from five depth intervals 0-20, 20-40, 40-60, 60-80 and 80-100 cm and their water contents and soil chemical properties (EC_e, pH, TDS, and Na, K, Ca and Mg) were measured every 7 days. Comparing the mean values of the differences between the studied soil properties amounts before and after leaching over the whole soil profile for different treatments showed that T1 had the highest leaching of TDS, EC_e, Na, K, Ca and Mg. However, the differences between the treatments were not statistically significant (p≤0.05) for Ca. T1 was statistically (p≤0.05) different from T4 for TDS, EC_e, Na, and Mg values and from T3 for K and Mg values. The graphical results showed that the HYDRUS-1D had the highest accuracy in simulating TDS, ECe and Ca in depth of 40 cm. The highest simulation accuracy resulted for Na in soil depth of 20 cm and for Mg, and K in the depth of 80 cm. The highest simulation accuracy of SWC was seen for the depth of 40 cm. For all treatments and properties, the values of R² ranged from 0.72 to 0.88, the RMES values were almost equal to the data standard deviations and the EF values ranged from 0.52 to 0.97, which indicated that the HYDRUS-1D software had a good ability to appropriately simulate water and salt transport in soil and predict water content and EC_e profiles, satisfactorily. Therefore, it should be used for better management of irrigation and leaching of saline soils over the region in the future.