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 ( NO3 - -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 of NO3 - -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 soil NO3 - -N content simulated by DNDC were combined to calculate the leachate NO3 - -N concentrations with good accuracy. The accumulative NO3 - -N leaching flux during the simulation year was 71.7 kg N ha(-1), with remarkable spatio-temporal variations on this hillslope. Hot spots of NO3 - -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 of NO3 - -N leaching was mainly controlled by soil texture and soil hydraulic properties. Hot moments of NO3 - -N leaching were observed after the applications of spring fertilizer (16 March) and basal fertilizer (30 October). The temporal variation of NO3 - -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.