Quantifying nitrogen loss and water use via regionalization and multiple‐year scenario simulations in the North China Plain

Background: Intensive winter wheat–summer maize ( Triticum aestivum L.– Zea mays L.) double‐cropping systems in the North China Plain often show high nitrogen (N) losses and water use causing harmful threats to the environment. Methods: Continuous multiple‐year simulations (31 years) with the HERMES model were used to spatially quantify N and water losses at county scale in order to identify best‐practice management applications. Results: Results show simulated annual long‐term N losses for the investigated Quzhou County, Hebei Province of 297 kg N ha −1 under common farmers practice treatment (FP) and 102 kg N ha −1 under optimized treatment including model derived N fertilizer recommendation and automated irrigation (OPTai). Total losses by N leaching, volatilization and denitrification were 57% (FP) and 40% (OPTai) of the applied fertilizer N, respectively. Spatial differences in N losses were found due to survey‐specific differences of average N inputs among the townships. More than 260 kg N ha −1 y −1 of fertilizer input, N losses of 190 kg N ha −1 y −1 , and around 116 mm y −1 of irrigation water could be saved on average by optimized treatments compared to farmers practice. Conclusion: On clay loam soil only OPTai could maintain crop yield without drought stress. The optimized treatments had the lowest N inputs and N losses but they did not seem to be able to sustain the organic N pools.