Abstract:In order to explore the effects of different green manure cover on the runoff and nutrient loss of the citrus orchard on the purple soil slope farmland, four treatments (Lolium perenne L., Vicia villosa Roth var, Orychophragmus violaceus, and clean tillage control) were set up to quantitatively monitor the runoff and nitrogen and phosphorus loss of different treatments under natural rainfall conditions. The results showed that compared with the clean tillage control, green manure cover significantly reduced the surface runoff by 8.7%~27.0%, total nitrogen loss by 30.1%~50.6%, and total phosphorus loss by 32.4%~62.9%.However, the effects of green manure cover on runoff and nutrient control were different among different varieties, and the trend of overall performance was Lolium perenne L.>Vicia villosa Roth var. >Orychophragmus violaceus. Compared with clean tillage control, Lolium perenne L. treatment reduced the total loss of total nitrogen, soluble nitrogen, nitrate nitrogen, and ammonium nitrogen in runoff by 50.6%, 47.0%, 49.5%, and 48.1% respectively; total phosphorus, soluble phosphorus, and total loss of phosphate was reduced by 62.9%, 62.6%, and 62.6% respectively. In addition, the effect of green manure cover on different nutrient forms were also different, and the loss of soluble nitrogen and particulate phosphorus in the runoff were the largest, accounting for 59.6%~67.0% and 68.6%~71.8% of total nitrogen and total phosphorus, respectively. In summary, green manure cover cultivation can effectively reduce the runoff and nitrogen and phosphorus loss of citrus orchards on purple soil sloping farmland. Among them, Lolium perenne L. and Vicia villosa Roth var. cover were the best. Taken together, our results provide reference for water and soil conservation and non-point source pollution prevention and control in citrus orchards on purple soil slope farmland.