Simulation of Drainage Volume and Nitrogen Loss Load in Paddy Fields under Different Irrigation and Drainage Modes and Hydrological Years

Controlled irrigation and drainage technology for rice is crucial water management that has been widely promoted in northeastern China. It is of great significance to clarify the response mechanism of the drainage volume and nitrogen loss load in the paddy field for realizing water saving, emission reduction, pollution control and high yield in rice-planting areas. In this study, we conducted field experiments and simulations on drainage volume and nitrogen loss load regulations of paddy fields in a cold black soil region under different hydrological years and irrigation and drainage modes. The key parameters for simulating drainage volume and nitrogen loss load in paddy fields using DRAINMOD-NII were determined by combining field experiments, data analysis, and numerical simulation. The results showed that the simulated drainage volume and nitrogen loss load showed a high coefficient of determination with the observed results, which were all above 0.83. The Nash-Sutcliffe efficiency coefficient ranged from 0.72 to 0.97 in model calibration and verification, indicating that the model effectively simulated drainage volume and nitrogen loss load in paddy fields under controlled irrigation and drainage in the cold black soil region. The paddy field drainage volume was not only influenced by rainfall frequency but also by the distribution of rainfall. Compared with traditional irrigation and drainage, the controlled irrigation and drainage significantly reduced the irrigation amount by 39.07% and increased rainwater utilization efficiency by 13.07%. It also reduced the drainage volume by 44.71% and NO3--N and NH4+-N loss load by 59.38% and 44.96%. The controlled irrigation and drainage mode optimized natural rainfall resources and increased irrigation water productivity and rice yield by 97.85% and 16.88%, respectively. Controlled irrigation and drainage outperformed the traditional mode in different hydrological years, with more pronounced effects in dry years, which highlights its significant value in practical agricultural production.