Application of HYDRUS2D for Dynamical Assessment of the Influence of Irrigation Management on Controlling Soil Cardinal Temperatures

Soil cardinal temperatures are one of the affective factors on biological properties of crops and highly affect root growth and consequently, water and nutrient uptake. Since soil water content has a considerable contribution in controlling soil temperature, predicting the probable consequences of applying a specific irrigation strategy may help with selecting a suitable method aiming at increasing water and nutrient use efficiency. Therefore, in this research, HYDRUS2D was applied for dynamical assessment of the influence of different irrigation strategies on the spatial and temporal pattern of soil temperature variations and the projected uncertainties through the simulation approach. Simultaneous soil water content and soil temperature data was collected by using IDRG SMS T-2 sensors installed in maize rooting zone under full irrigation (FI), deficit irrigation (DI) and partial root-zone drying (PRD) during 2010 growing season. Simultaneous soil water content and soil temperature data was collected by using IDRG SMS T-2 sensors installed in maize rooting zone. The calibration process was done using the continues data collected after 10 irrigation events in all treatments, and the validation process was carried out using daily variations of soil temperature. Finally, the model uncertainty was assessed by calculating the spatial and temporal error variance. Based on the root mean square error (RMSE) and model efficiency (EF) in the validation process, HYDRUS2D could accurately simulate soil temperature (RMSE=0.02-0.42 oC, EF=0.71-0.92) and the minimum and maximum RMSE in estimation soil thermal regimes was corresponded to FI and PRD treatments, respectively. the lowest uncertainty domain for simulating soil temperature under FI, PRD and DI treatments was observed in 60-80 cm soil depth, and the estimated errors for these treatments were, respectively, 0.6±0.2, 5.9±2.3 and -5.4±2 percentage, respectively. Moreover, the highest uncertainty domain for FI, PRD and DI treatments was corresponded to 20-40 cm, 0-20 cm and 60-80 cm soil depth, respectively, and accounted for 9±5, -0.6±3.04 and 13.7±5.3 percentage, respectively. Based on the results, applying PRD would decrease the number of stress days through controlling soil cardinal temperatures in the domain of 9-28 oC which led to providing a better condition for root growth especially in the soil depths beyond 40 cm.