Study on the In-Field Water Balance of Direct-Seeded Rice with Various Irrigation Regimes under Arid Climatic Conditions in Egypt Using the AquaCrop Model

Abstract

Crop growth models are cost-effective and user-friendly tools for decision-makers to develop efficient in-field management strategies. These models are particularly important in countries such as Egypt, where the risk of water scarcity is inevitable. The present study aimed to examine the in-field water balance of direct-seeded rice (Giza 178) under various irrigation regimes and arid conditions during two growing seasons (2019 and 2020). Four irrigation regimes, namely, continuous flood irrigation with a fixed water depth of 5 cm, and 3-, 6-, and 10-day irrigation frequencies (FI, 3IF, 6IF, and 10IF, respectively), were arranged in a randomized complete block design with three replicates. Then, the feasibility of using AquaCrop in simulating direct-seeded rice development and in-field water balance was assessed. Five statistical indicators, including normalized root-mean-squared error (NRMSE), index of agreement (d), coefficient of determination (R2), Nash–Sutcliffe efficiency coefficient (EF), and percent deviation (Pd), were used to evaluate the performance of AquaCrop. The field trial results demonstrated that both the 3IF and 6IF irrigation regimes were the best for achieving the highest biomass (21.0 t·ha−1, under 3IF), yield (9.8 t·ha−1, under 3IF), and saving irrigation water (18.3–22.4%, under 6IF), making them the best to apply in Egypt. Moreover, the AquaCrop simulation results showed a good correlation between the observed and simulated rice yield (Y) in both seasons (R2 = 0.99 and 0.98 in 2019 and 2020, respectively). AquaCrop showed excellent performance in simulating canopy cover (CC) and biomass (B) during both growing seasons (5.0 ≤ NRMSE ≤ 15.0, 0.97 ≤ d ≤ 0.99, 0.92 ≤ R2 ≤ 0.99, and 0.92 ≤ EF ≤ 0.99). In addition, the model showed acceptable performance in simulating in-field water balance components. Reasonably good model efficiency was recorded in simulating crop actual evapotranspiration (ETact). Meanwhile, the average Pd for percolation (P) was between −15.3% and 5.4% during both growing seasons. Overall, AquaCrop showed adequate accuracy in simulating CC, B, Y, ETact, and P but relatively low efficiency in simulating ETact and P under severe water scarcity. Therefore, AquaCrop may serve as a valuable tool for irrigation management and crop yield prediction even in arid regions, such as Egypt.