Adaptation under Integrating Seasonal and AQUACROP Simulations to Evaluate Soil Moisture and Drip Irrigation Effects on Tomato Production in Southern Ethiopia

Seasonal variation analysis revealed slight differences in crop growth and model performance between the calibration (Season 1) and validation (Season 2) periods. The simulated and observed results showed that biomass (BM) and dry yield (DY) exhibited minor seasonal reductions, while soil water content (SWC) and water productivity (WPET) showed modest increases. Specifically, biomass decreased by 1.6%, from 8.788 t ha⁻¹ in Season 1 to 8.650 t ha⁻¹ in Season 2, whereas dry yield declined by 1.9%, from 5.458 to 5.357 t ha⁻¹. These slight decreases are mainly attributed to higher mean air temperature and reduced mid-season rainfall during the validation period, which increased crop water stress and evapotranspiration demand under deficit irrigation treatments. In contrast, the mean soil water content increased by 1.3%, from 276.1 mm in Season 1 to 279.6 mm in Season 2, likely due to enhanced late-season rainfall and improved soil moisture retention under full irrigation. The most notable seasonal improvement was observed in water productivity, which increased by 10.0%, from 1.65 to 1.81 kg m⁻³, indicating more efficient water use and higher transpiration efficiency during the slightly drier validation season. Overall, AquaCrop demonstrated stable performance across both seasons, effectively capturing the temporal variability in crop growth and soil moisture dynamics. Although small fluctuations occurred due to climatic variability, the model maintained strong correlations for canopy cover (r ≥ 0.96), biomass (r ≥ 0.98), and soil water content (r ≥ 0.94), confirming its reliability for simulating seasonal crop responses under different irrigation regimes.