湿润区坡地香根草植物篱农作措施对土壤侵蚀和养分的影响

为了解植物篱农作措施的侵蚀、养分循环特征，促进湿润半湿润地区坡地可持续利用。在三峡库区王家桥小流域建立了6个香根草(Vetiveria zizanioides)植物篱农作小区，包括：传统坡地耕作对照小区(C);单纯植物篱坡耕小区(H);植物篱+无机肥坡耕小区(HI);植物篱+有机肥坡耕小区(HO);植物篱+覆盖+无机肥坡耕小区(HIM);植物篱+无机肥+有机肥+覆盖坡耕小区(HIOM)。试验结果表明：N素损失的主要途径是径流携带，各植物篱小区的N损失达对照小区的2～3倍。泥沙携带是P素流失的主要形式，其径流损失几乎可以忽略。K素的径流携带损失非常严重，但低于其泥沙侵蚀损失。N、K平衡与作物产出正相关，越是高产区其养分平衡状况越容易出现亏损。单纯的植物篱措施有较明显的控制土壤流失功能，但减流效益不明显。施肥、覆盖措施，以及作物产出对植物篱农作措施的侵蚀有巨大影响。采取覆盖结合施肥的植物篱小区(HIOM和HIM)，水土效益最高，但投入高，产投比过低；植物篱配合有机肥或者无机肥措施小区(HO和HI)，水土保持效益和产投比均比较理想。综合生态、经济效益，应该优先推广HO和HI农林复合坡耕经营模式。

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.