Effects of Aboveground and Underground Parts of Vetiveria zizanioides L.Hedgerow on the Nitrogen Loss of Purple Soil on Slope Farmland in the Three Gorges Reservoir Area

Hedgerow can influence not only on the erosion and runoff process,but also on the related nitrogen loss on slope farmland.However,the effect of aboveground part and underground part of hedgerow on nitrogen loss is still not clear.Simulated rainfall experiments were conducted at 1 rainfall intensity (60mm/h),2 slope gradients (15° and 25°) and 3 slope conditions (Control check,Hedgerow and Only hedgerow roots) to analysis the sediment amount,runoff amount,and the content and loss of nitrate nitrogen (NO^-₃-N),ammonia nitrogen (NH⁺₄-N) and total nitrogen (TN) via them.The results indicated that the hedgerow could effectively reduce the sediment amount and runoff amount,and the nutrient was mainly lost via sediment.The nitrogen content in runoff could be reduced by hedgerow while that could be increased in sediment,and finally the hedgerow could effectively reduce the nutrient via both runoff and sediment.The reduction effect can attribute to the combination of aboveground and underground parts of hedgerow,and the average contribution rates of aboveground part and underground part of hedgerow to the reduction of nutrient loss amount for NO^-₃-N,NH⁺₄-N,TN were 43.97% and 56.03%,44.12% and 55.88%,46.91% and 53.09%,respectively.The results could deepen the understanding of the influence mechanism of Vetiveria zizanioides hedgerow on nitrogen loss of slope farmland,and provide a scientific basis for the sustainable and efficient utilization of soil and water resources of slope farmland in the TGRA.