Evaluating soil salt dynamics in a field drip-irrigated with brackish water and leached with freshwater during different crop growth stages

Abstract

Abstract Irrigation with brackish water is a possible solution to alleviate freshwater shortages in arid and semi-arid regions. However, necessary measures need to be taken to leach accumulated salts out of the root zone. This can be accomplished by leaching with freshwater applied by surface irrigation (LFSI), which needs to be optimized to improve the leaching efficiency. An experiment in a field drip-irrigated with brackish water was carried out during 2017 and 2018 to evaluate the effects of leaching (or no leaching (T0)) during the corn elongation (T1), tasseling (T2), and grain-filling (T3) stages. The HYDRUS (2D/3D) model was calibrated and validated using experimental data collected in 2017 and 2018, respectively. The results of numerical simulations were in good agreement with measurements, which is electrical conductivity (ECw), with mean relative errors of 11.9%, 10.1%, 10.6%, and 9.2% for the T1, T2, T3, and T0 treatments, respectively, during the validation periods. LFSI during the corn elongation stage (T1) had the shortest duration of “high salinity stress” which lasted 42, 56, 57, and 82 days for the T1, T2, T3, and T0 scenarios, respectively. The highest rate of salt reduction in the root zone (i.e., the desalination rate) occurred when LFSI was applied during the corn grain-filling stage (T3). The desalinization rates were 59%, 68%, and 69% in the T1, T2, and T3 treatments, respectively. The cumulative salt flux at a depth of 40\xa0cm increased by 2.0%, 16.3%, and 34.7% for T1, T2, and T3, respectively, compared to T0. Two-dimensional simulations of ECe distributions revealed that the “high salinity stress” area in the soil profile after LFSI was 4%, 48%, and 92% higher for T0 than for T1, T2, and T3, respectively. The simulations showed that optimal leaching time was about 41 days after sowing, which led to the lowest duration of the “high salinity stress” period and a relatively high desalination rate of 59%.