Abstract:The present study aimed to reveal the effects of intercropping on soil runoff and lateral seepage nitrogen (N), phosphorus (P) loss in different types of slope farmland. A runoff and leaching simulating experiment was conducted, different types of soil (red soil and purple soil) and slopes (8° and 15°) and planting patterns maize (Zea mays L.)/soybeans (Glycine max L.) intercropping and mono-maize and mono-soybeans) were designed, the changes of N and P concentrations in runoff and lateral seepage under the influence of various factors were analyzed. The results showed that:(1) In the case of the total nitrogen (TN) and total phosphorus (TP) of runoff:under different slope in red soil, compared with mono-soybean, intercropping has different reduction effect on TN, the reductions were 27.5% and 30.8%, respectively, and the TN under intercropping was the lowest, which was 0.75 mg/L at the slope of 8°. Under the slope of 8° in purple soil, compared with mono-soybeans and mono-maize, the reduction of intercropping on TN of runoff was more obvious, and the reductions were 97.8% and 89.8%, respectively. Compared with mono treatment, intercropping had the different reduction on TP of runoff. However, the TP of runoff increased from the slope of 8° to 15°. (2) For the lateral seepage TN, TP, under the slope of 8° and 15° in the red soil, compared with mono-maize, intercropping had a greater reduction of the lateral seepage TN, which had 87.9% and 86.8% reduction, respectively, as well as the lowest concentration of TN was 2.91 mg/L at 8°; under the slope of 8° and 15° in purple soil, the reduction of intercropping on TN of lateral seepage were 50% and 80%, respectively. Compared with mono-maize, intercropping also had the different reduction on TP of lateral seepage; and the TP under the slope of 8° in red soil of intercropping was the highest with 0.25 mg/L, and the TP under the slope of 15° red soil of intercropping was the lowest with 0.07 mg/L. The output of N and P in soil was different under different slope treatments and the total loss of N and P in runoff or lateral seepage would increase with the slope increasing. In conclusion, the maize/soybean intercropping system had a certain effect on the reduction of N and P concentration in the runoff and lateral seepage. For red soil and purple soil, the reduction of the loss of N and P in the soil of slope farmland might be different because of their physicochemical properties. Therefore, controlling the loss of N and P in slope farmland should consider all kinds of factors, which is of great significance to protect the water environment of Dianchi Watershed.