Investigating the spatio‐temporal variations of nitrate leaching on a tea garden hillslope by combining HYDRUS‐3D and DNDC models

Spatio‐temporal variations of nitrate‐nitrogen (NO 3-‐N) leaching is driven by both soil hydrology and biogeochemistry. However, the widely used soil hydrology and biogeochemistry models have their weaknesses in simulating soil N cycling and soil water movement processes, respectively. In this study, we proposed an alternative approach by simply combining the HYDRUS‐3D and DNDC models to investigate the spatio‐temporal variations ofNO 3-‐N leaching on a representative tea garden hillslope in Taihu Lake Basin, China. Results showed that the soil hydrology and N cycle were well simulated by HYDRUS‐3D and DNDC models, respectively. Based on the leaching equation, the soil water flux simulated by HYDRUS‐3D and soilNO 3-‐N content simulated by DNDC were combined to calculate the leachateNO 3-‐N concentrations with good accuracy. The accumulativeNO 3-‐N leaching flux during the simulation year was 71.7 kg N ha −1 , with remarkable spatio‐temporal variations on this hillslope. Hot spots ofNO 3-‐N leaching were observed in blocks 24, 27, 31, 34, 37, and 40 with accumulative leaching fluxes > 82.0 kg N ha −1 y −1 . The spatial variation ofNO 3-‐N leaching was mainly controlled by soil texture and soil hydraulic properties. Hot moments ofNO 3-‐N leaching were observed after the applications of spring fertilizer (16 March) and basal fertilizer (30 October). The temporal variation ofNO 3-‐N leaching was mainly controlled by precipitation and the spring fertilization. Methods and findings of this study will be benefit for the risk assessment of non‐point source N loss and the precise agricultural management.