Interactive effects of environmental factors and fertilization practices on soil nitrate leaching and tea productivity in Tianmu Lake Basin, China

Although the effects of fertilization practices and environmental factors on tea yield and NO3−–N leaching have been acknowledged, the interactive effects of these influencing factors remain unknown. These effects were investigated in this study using the denitrification–decomposition (DNDC) model, which was validated using field data collected from a typical tea garden hillslope in the Tianmu Lake Basin, China. Environmental factors such as temperature, precipitation intensity, slope, saturated hydraulic conductivity (Ksat), and fertilization practices (fertilizer amount and type) were combined to construct 1080 scenarios. The results revealed that DNDC achieved acceptable performance in simulating NO3−–N leaching under the application of a compound fertilizer (CF) and a slow-release fertilizer (SF). During the calibration period, the Nash–Sutcliffe efficiency (NSE) values were 0.48 and 0.24. During the validation period, the NSE values were 0.71 and 0.67. Scenario analysis indicated that precipitation intensity (p < 0.001), saturated soil hydraulic conductivity (Ksat) (p < 0.001), fertilizer amount (p < 0.001), and fertilizer type (p < 0.001) significantly influenced the leaching flux of NO3−–N and tea yield. The interactive effects of different factors also varied across the different types of fertilizers. The amount of fertilizer had the most significant impact on NO3−–N leaching, with relative contribution rates of 70% and 53% for compound and SFs, respectively. As CF application increased, there was a significant increase (93%) in the average flux, whereas SF application resulted in an increase of only 76%. The highest contribution rate in terms of tea yield was observed for the amount of fertilizer under CF application at 44%. However, the highest contribution rate under SF application was attributed to Ksat at 51%. The application of SFs resulted in a higher yield improvement rate than that of CFs as the fertilizer amount increased, with respective rates of 15% and 8%. Additionally, environmental factors, excluding temperature, exerted opposite effects on tea production and NO3−–N leaching flux. These findings contribute to optimizing fertilization management in tea plantations by integrating multiple environmental factors to control nonpoint nitrogen loss. Future research should conduct long-term monitoring of tea garden yield and nitrogen loss to accurately assess the impact of SF application on the ecological and economic benefits of tea gardens.