Biochar-based fertilizer can mitigate nitrogen runoff loss from the citrus orchard as comparison with organic...

China has the largest citrus cultivation area globally, where it faces a high risk of nutrient loss from the excessive chemical fertilizer application. Organic and biochar-based fertilizers have been shown to mitigate nutrient losses. However, research on mitigating nutrient runoff losses from citrus orchards remains limited. This study conducted a 2-year field experiment in southern China, with four treatments including no-fertilizer (CK), chemical fertilizer (CF), organic fertilizer substitution (COF), and biochar-based fertilizer (BF). Nitrogen and phosphorus losses via surface runoff and their inputs from precipitation were monitored. The result indicated that the BF treatment reduced total nitrogen runoff losses by 18.35% compared with COF, primarily by decreasing nitrate nitrogen losses following precipitation events. Nitrogen and phosphorus deriving from precipitation constituted significant sources in runoff. Different from runoff losses of ammonium nitrogen closely linked to recent fertilization activities, nitrate nitrogen losses were supposed mainly to originate from rain-eroded soil particles, which also led to phosphorus losses. This study provides valuable insights for mitigating non-point source pollution from citrus orchards.