Simulation of water and heat transport in drip-irrigated sandy soil under mulched conditions

Extremely high temperatures during summer and limited water availability are characteristics of arid and semi-arid regions. Drip irrigation offers a great potential for getting high water use efficiency under such situations. Therefore, a field experiment was carried out to quantify the effects of wheat straw mulch on soil water and thermal regime in the drip-irrigated sandy soil under uncropped condition at Regional Research Station Balsamand (29° 07^/N, 75° 28^/E, 225 m elevation) of CCS Haryana Agricultural University, Hisar. The field experiment consisted of two treatments, namely 1) control (no mulch), and 2) wheat straw mulch. Two-dimensional Hydrus-2D numerical model was used to estimate hydraulic parameters using inverse modeling for simulating water and heat transport under control and mulch field conditions. Soil water content and hourly temperature were measured at different depths. Wheat straw mulch increased the soil water storage by 1.9 L m⁻² compared to control. The mulch decreased the daily soil temperature amplitude and average temperatures measured at 0.05, 0.10 and 0.20 m depths than those in control. Hydrus-2D model performed well for simulating water flow in control with RMSE values ranging from 0.008 to 0.012 m³ m⁻³, and in mulch with RMSE values of 0.010 to 0.012 m³ m⁻³. The model predicted that soil water storage decreased and evaporation increased by increasing the drip irrigation frequency under both the treatments. The Hydrus-2D also simulated diurnal soil temperatures reasonably well under control and mulch treatments with RMSE values ranging from 0.8 to 1.9°C. Thus, mulching is beneficial in conserving soil moisture and moderating soil temperature in arid regions. The Hydrus-2D model was found to be a useful tool for simulating water and heat flow in the drip-irrigated sandy soil under field conditions.