Comparison of Different Lateral Depths and Irrigation Scenarios for Optimal Sorghum Cultivation using HYDRUS-2D

This study aims to evaluate the HYDRUS-2D model’s ability to simulate soil water content in the soil profile under sweet sorghum with drip irrigation at different lateral depths and irrigation levels. It also aims to determine the optimal lateral depth by numerically evaluating various depth scenarios. The study was carried out in Antalya, Turkey, in 2020 and 2021, using a randomized block design with three replications. Three irrigation levels, 33% (S33), 66% (S66), and 100% (S100) of reference evapotranspiration, were applied when cumulative ET₀ reached 25 ± 5 mm. Two lateral depths, 25 cm (D25) and 50 cm (D50), were used. Soil water contents measured at 20, 40, and 60 cm were used in both the calibration and validation phases. To examine the effect of lateral depth on soil water variations, five additional scenarios (20, 30, 40, 50, and 60 cm) were modeled using the same inputs. During the calibration phase, R² values ranged from 0.90 to 0.99, the root mean square errors (RMSEs) from 0.01 to 0.03 cm3 cm-3, and the mean absolute errors (MAEs) from 0.01 to 0.06 cm3 cm-3 at the three depths. It was concluded that the model provided the most consistent and reliable water content predictions at a soil depth of 40 cm. In contrast, no trend was observed during the validation phase, suggesting that the model's prediction accuracy varied with different soil depths. Additionally, model simulations indicated that a 30 cm lateral depth was the most suitable among the evaluated scenarios; however, this result is subject to the assumptions and constraints of the HYDRUS-2D modeling framework, in which only lateral depth was varied while other conditions were held constant.