Abstract: In-situ monitoring of runoff under artificial rainfall was performed in a runoff experimental field located at the Xiangxi River Valley to investigate characteristics of nitrogen loss with different patterns of runoff and soil loss in a sloping farmland of typical yellow-brown earth, which is highly susceptible to soil erosion. Results show that surface runoff differed sharply from interflow. During a storm event surface runoff accounted for 68.44% of the total runoff and interflow for 31.56%. The loss of TN, DN, NO3^--N and NH₄⁺-N with runoff was 1.869, 1.524, 1.404 and 0.018kg· hm^-2, respectively. All the forms of N, except NH₄⁺-N, were lost with interflows, which contributed over 70 %. The N lost with surface runoff was mainly interflow particulate N, while that with soluble TN. The total loss of total nitrogen with runoff during the rainstorm reached 2.90kg· hm^-2 of which 14.56% was lost with the water in surface runoff, 35.51 % with the silt in surface runoff and 49.93 % with interflow. Therefore, it is critical to adopt cultivation practices that are capable of raising the soil capacity of holding water and nutrients and controlling nutrient losses with interflow in management of of non-point source pollution.

Key words: Three Gorges Reservoir, Xiangxi River, artificial rainfall, nitrogen, loss characteristics