Abstract
Water is extremely sacred resource, and there is a need to preserve it for future generations. Water is life because no one can live without water. A significant portion of water is consumed for agriculture, industrial production, and domestic purposes. In agriculture, most crops are irrigated using traditional methods, which result in greater water waste. Drip irrigation is the most efficient irrigation system, which saves water by slowly delivering water to the roots of crop. The information on water movement in the root zone during drip irrigation is essential for studying soil water movement and plant water uptake across different soil layers to plan irrigation scheduling. Appropriate calibration and validation of a numerical model can reduce the time and cost required to study soil water movement in the root zone. HYDRUS is one such model; a suite of Windows-based modeling software can be used to simulate soil water movement. Hence, the experiment was conducted during kharif 2022 at the field irrigation laboratory, Department of Soil and Water Conservation Engineering, Dr. N.T.R. College of Agricultural Engineering, Bapatla, Andhra Pradesh, to study soil water dynamics in a drip-irrigated sweet corn crop using the Hydrus-1D model. The study primarily aimed to calibrate, validate, and simulate soil moisture dynamics for a sweet corn crop under different irrigation scenarios. The experiment consisted of six treatments with different irrigation levels through drip irrigation namely T1(0.6 ETc), T2(0.7 ETc), T3(0.8 ETc), T4(0.9 ETc), T5(1.0 ETc) and T6(without drip irrigation i.e., traditional watering method). A randomized block design with four replications of each treatment was laid out in the field, resulting in a total of 24 plots. Crop water requirement was estimated as 332 mm using CROPWAT 8.0 model. A total of 5 access tubes were installed in the first replication of each drip-irrigated treatment. Frequency Domain Reflectometry (FDR) was used to measure soil moisture content through the installed access tubes in the field up to a depth of 100 cm. The moisture reading was taken before the start of irrigation, immediately after irrigation, 3h after irrigation, 6h after irrigation, and 24h after irrigation. Calibration and validation of the model were done for 25 DAS and 55 DAS, respectively. The statistical indices of the observed and predicted values during validation indicate that there is a good agreement between observed and predicted values during calibration with the high values of NSE (99.29 to 99.39 %) & R2 (0.9968 to 0.9987) and low values of RMSE (0.083 to 0.122) & RE (2.67 to 2.95). Thus, the model performed well with the calibrated hydraulic conductivity parameter. Simulation of soil moisture was performed for the entire crop-growing period using calibrated and validated parameters in the Hydrus-1D model. In a drip emitter with 2 lph, soil moisture content in the top layers up to 50 cm depth is well distributed and holds sufficient water in the root zone. There were no percolation losses observed below the active root zone during the application of water at a low rate (2 lph) through drip irrigation. Hence, the Hydrus-1D model can be effectively used to study the moisture movement in the soil.