Assessment of AquaCrop Model in Simulating Sugar Beet Canopy Cover, Biomass and Root Yield under Different Irrigation and Field Management Practices in Semi-Arid Regions of Pakistan

The AquaCrop model was analyzed for simulating sugar beet crop production under four irrigation regimes, three mulching conditions and three furrow irrigation systems in semi-arid region of Pakistan. Irrigation regimes were full irrigation (FI), 20% deficit irrigation (DI₂₀), 40% deficit irrigation (DI₄₀) and 60% deficit irrigation (DI₆₀). The mulching practices were No-mulch (NM), black film mulch (BFM) and straw mulch (SM). The furrow irrigation systems were conventional ridge-furrow (CRF) system, medium raised-bed (MRB) system and wide raised-bed (WRB) system. The model was calibrated and validated using the independent data sets of full irrigation and deficit irrigation regimes collected during 2011–12 cropping season. The model performance was evaluated by using different statistical indicators such as Root Mean Square Error (RMSE), index of agreement (d_index), and Nash–Sutcliffe Efficiency (NSE). These indicators showed that the model fairly simulated sugar beet canopy cover for all treatments with 3.00 ≤ RMSE ≤ 16.89, 0.84 ≤ d_index ≤ 0.97, and 0.76 ≤ NSE ≤ 0.99. For biomass and root yield, the model performance was excellent under all full irrigation (FI) and mild deficit irrigation (DI₂₀) treatments with RMSE ranged between 0.07 and 1.17, d_index between 0.48 and 0.84, and NSE between 0.42 and 0.86, respectively. However the low values of d_index (0.10 and 0.13) and NSE (−69.32 and −30.63) showed that the model overestimated both the biomass and root yield when 20% deficit irrigation was applied without mulch in WRB system. The model also over estimated the yield and biomass when 40% deficit irrigation was applied in CRF system. The highest overestimation (d_index: 0.10 to 0.11; NSE: −50.92 to −70.55) was observed when highest stress level (DI₆₀) was applied in the presence of BFM in CRF system. Based on the model’s overall performance, the AquaCrop application is recommended for developing efficient farm water management strategies in the semi-arid regions.