Abstract

The need for decision-support tools to aid well-informed water use has become a critical priority in irrigated agriculture as climate change effects prolong dry spells, increase variability in rainfall, and exacerbate the water scarcity situation. The study's objective is to evaluate the performance of the AquaCrop model (version 7.1) in simulating yield, biomass, and crop evapotranspiration (ET) of UC 82B tomato cultivar under drip irrigation in Kaduna, Nigeria. The methodology comprised a calibration of the model in the first irrigation season using field data from nine growth-stage-based deficit irrigation treatments and a full irrigation treatment, and its validation in the second season. The simulation results were evaluated using standard statistical indicators. Both calibration and validation results showed excellent agreement between measured and simulated values, with r2 values > 0.90 for fruit dry yield and biomass, and ≥ 0.90 for ET. The prediction errors were low: ≤ 5.4% for yield, 4.7% for biomass, and 5.2% for ET, implying very strong model performance. The Nash–Sutcliffe efficiency (NE) ≥ 0.80, normalized root mean square error (NRMSE) ≤ 5%, and confidence index (c) > 0.85 indicated a high simulation efficiency of AquaCrop 7.1 for UC 82B tomatoes, and a demonstration of its reliability in predicting tomato crop yield and water use under varied irrigation regimes. The calibration of AquaCrop 7.1 for UC 82B tomato is unique as it provides a cultivar- and region-specific model for drip-irrigated, growth-stage-based deficit conditions, appropriate for promoting sustainable water resources management within Nigeria's Northern Guinea Savanna agro-ecological zone.

Key words: Simulation, AquaCrop, Deficit irrigation, Tomato, Kaduna