Mitigating non-point source pollution in tea plantations: SWAT modeling and field validation of slow-release fertilizers.

Non-point source (NPS) pollution from tea plantations can significantly affect watershed water quality. To mitigate NPS pollution, this study used the Soil and Water Assessment Tool (SWAT) to simulate the impacts of conventional and slow-release fertilizers on tea plantations and to develop best management practices (BMPs) for phosphorus reduction in the Jingmei River watershed, Taiwan. The model was calibrated at both watershed and field scales, showing high accuracy in simulating streamflow, sediment, nitrate nitrogen, and phosphorus. Simulation results indicated that slow-release fertilizers reduced phosphorus losses by 0.96 kg/ha at the field scale and 1.16 kg/ha at the watershed scale, equivalent to constructing 36-60 m² of low-impact development (LID). Each bag of slow-release fertilizer reduced phosphorus by 5.04-8.02 g at the field scale and 7.38-8.35 g at the watershed scale, highlighting their effectiveness in phosphorus reduction. This study suggests that combining slow-release fertilizers with LID measures provides a sustainable approach for managing tea plantations and mitigating nutrient pollution in river systems.