等高固氮植物篱技术——山区坡耕地保护开发利用的有效途径

固氮植物篱近年来被热带地区用作防治坡耕地的水土流失和肥力退化的有效手段。在地处亚热带金沙江干热河谷区的中国科学院成都生物研究所宁南持续发展实验站的研究结果表明：与传统顺坡耕作方式相比，利用新银合欢(L．1eucocephala)或山毛豆(T．candida)在坡耕地上每隔4m培植高密度的双行等高植物篱可使坡耕地的径流量平均减少49．6％以上，土壤侵蚀及其产生的养分流失均减少98％以上，土壤有机质、全氮、阳离子交换量等养分有很大程度的恢复和改善。农作物产量得以维持和提高，这说明等高固氮植物篱对我国亚热带坡耕地的水土保持和土壤改良同样具有十分良好的效果。

Contour Hedgerow Intercropping for Exploitation and Conservation of Slope Cropland in Mountain Areas

Increasing population pressure drives farmers cropping even in steep lands, which induced land degradation such as soil erosion, nutrient loss, and seasonal drought. Field experiments were conducted to test the effects of contour hedgerow system on slope croplands in Ningnan County, which lies in the dry and hot valley of Jinsha River in the southwestern Sichuan with more than 90 % of its rainfall in monsoon. The results of four treatments with three replicates (CK: slope tillage, T2 and T3: Leucaena leucocephala hedgerow with and without fertiliser; and T4: Tephrosia candida hedgerow with fertiliser) showed that L. leucocephala and T. candida hedgerow planted apart 4m in slope reduced surface runoff to less than 49.6 % of the control, i.e., runoff were very large in CK, reaching more than 303 t/hm 2 and 568 t/hm 2 in Tangguanyao and Masangping Sites, respectively. However, runoff were markedly reduced to less than 110 t/hm 2 and 282 t/hm 2 respectively under contour hedgerows system, and soil loss were reduced to less than 2 % of the control due to obstruction by densely planted hedgerow barriers. Utilizing hedgerows' pruning as green manure ameliorated soil fertility of degraded soil and increased crops yield. Multi_purpose hedgerows can also provide fodder and firewood. The contour hedgerow has shown integrated benefits for sustainable agricultural development in mountain areas.