Application of HYDRUS-1D model for simulating water and nitrate leaching from continuous and alternate furrow irrigated rapeseed and maize fields

Different simulation models were used to evaluate drainage and nitrogen fertilizer movement to groundwater. The objectives of this study were to evaluate the HYDRUS-1D model for simulation of water and nitrate leaching in different nitrogen fertilization rates (as urea) and variable and fixed alternate furrow irrigation (VAFI, FAFI) and continuous furrow irrigation (CFI) of rapeseed and maize planted in 36 field lysimeters. Results indicated that seasonal drainage in rapeseed field was reduced 39% and 72% under VAFI and FAFI, respectively compared with CFI. These reductions for maize were 40% and 57%, respectively. For rapeseed, NO3–N leaching was reduced 40% and 69% under FAFI and VAFI compared with that obtained under CFI, and it was increased up to 55% by increasing N application rate to 200–300 kg ha−1 compared to 0 N application rates. For maize, NO3–N leaching was reduced similarly under VAFI and FAFI (56%) compared with CFI, and it was increased up to 67% by increasing N application rate to 300 kg ha−1 compared to 0 N application rates. Furthermore, for both crops, HYDRUS-1D model was able to simulate deep percolation water (NRMSE of 0.11 and 0.094 for rapeseed and maize, respectively), NO3–N leaching (NRMSE of 0.14 and 0.18 for rapeseed and maize, respectively) with a very good accuracy even though the water and NO3− flow in soil surface layer was 2-dimensional. The measured and predicted crop N-uptake was different and this difference was attributed to the excluding root nitrogen uptake in the measured values and neglecting N mineralization, denitrification and microbial immobilizatrion processes.