Soil nitrate leaching of tea plantation and its responses to seasonal drought and wetness scenarios

Abstract Although the frequency and intensity of seasonal drought and wetness are increasing under climate change background, their effects on soil nitrate nitrogen (NO3--N) leaching have remained unclear. In this study, validated by the field data on a typical tea garden hillslope in Taihu basin, China, the Decomposition-Denitrification (DNDC) model was used to investigate these effects. The decennial drought, decennial wetness, and normal conditions of different seasons were combined to construct 31 scenarios. Results showed that seasonal drought decreased annual NO3--N leaching, with a reduction of 6.52%−18.70% (one-season drought), 18.62%−29.68% (two-season drought), 36.64%−43.99% (three-season drought) and 51.44% (all-season drought) relative to the normal scenario. Except the spring drought, drought in other seasons had legacy effects that increased NO3--N leaching in their succession seasons. The legacy effect of summer drought even continued till the summer of next year. Seasonal wetness increased annual NO3--N leaching, with an increase of 2.58%−11.39% (one-season wetness), 10.04%−22.31% (two-season wetness), 19.50%−29.39% (three-season wetness), and 29.66% (all-season wetness) relative to the normal scenario. Autumn and winter wetness decreased the NO3--N leaching in their succession seasons, while spring and summer wetness had no such effect. Soil NO3--N leaching had positive correlations with precipitation (drought scenarios: r = 0.74; wetness scenarios: r = 0.54) and soil water seepage (drought scenarios: r = 0.62; wetness scenarios: r = 0.56). Weak correlation coefficients between soil NO3--N content and NO3--N leaching were also observed especially under spring drought (r = 0.17) and summer drought (r = 0.14). However, NO3--N leaching was not limited by soil NO3--N content after the application of basal fertilizer. Fertilization plus drought or wetness increased the risk of soil NO3--N leaching. These findings will be benefit for controlling the non-point N loss of tea plantation under the background of climate change.