Erosion and nutrient cycling in the Vetiveria zizanioides hedgerow intercropping system with fertilization or mulching measures in humid slopeland

It is very important to understand the effects of hedgerow system on nutrient cycling, which is one of the bases to improve sustainable slopeland use. Six treatments were established in 1996 in Three Gorges Areas(TGA) to examine how different fertilization and mulching techniques affect nutrient cycling in Vetiveria zizanioides intercropping system. They were: Sloping without hedgerow (C); Vetiveria zizanioides hedgerow(H); Vetiveria zizanioides Hedgerow + Mulching+inorganic fertilizer(HIM); Vetiveria zizanioides Hedgerow + inorganic fertilizer(HI); Vetiveria zizanioides hedgerow + organic fertilizer(HO); Vetiveria zizanioides hedgerow + Mulching + inorganic and organic fertilizer(HIOM). During three cropping seasons (May 1996-November 1997), nutrient inputs and exports were recorded. N was lost mainly through runoff compared with its loss by soil erosion. When mono-hedgerow combined with mulching and/or fertilization, N loss was two to four times than that of C. P was lost mainly through soil erosion whereas its loss through runoff could almost be neglected. K loss through runoff was serious, but that was still lower than its loss through soil loss. P balance was positive in the more nutrient input plot including HO, HI, HIM and HIOM, N and K were minus, however. Moreover, the degree of deficit was positive to crop production, which means the nutrient condition in the higher production plot should be measured timely and supply enough nutrient input to ensure their balances in the system. The benefits of Vetiveria zizanioides hedgerow on controlling erosion were affected by not only mulching or fertilization but by crop production. Mono-hedgerow (H) can play a good role in controlling soil erosion, but its runoff was identical to the C plot; Ratio of cost-benefit in HIM and HIOM was very low although its high effects on controlling erosion (only 14.3% of that from C); treatments of hedgerow with fertilization (HO, HI) had the higher ratio of cost-benefit and better effect on controlling erosion. Both amounts of soil loss and runoff generation were in an ascending order of C, H>HO, HI>HIM, HIOM. Based on the economic benefits and ecological effects, comprehensively, HO and HI should be preferential options for agroforestry in Three Gorges Areas.