The effects of planted and plowed Stylosanthes guianensis on degrading soil fertility in hilly countries of dry-hot valley

The development of rural economy and ecological restoration were restricted with high temperature and drought in the dry-hot valley of Yuanmou country. The climate and human practice made a degrading ecosystem, and one marked question here was soil fertility degradation. Leguminous forage Stylosanthes guianensis were introduced for years in degraded mountainous dry-hot valley of Yuanmou. Aims to reveal devotions of planting and plowing S. guianensis to degraded mountainous soil fertility, three soil types and two treatments planting experiment were tested in the dry-hot valley of Yuanmou country. The results show that: 1. S. guianensis could adapt to degraded mountain soil. There was a large number of nodules and root in three soil types, number of root nodule was 174.048-650.667 grain/individual plant, root biomass was 214.667-1710.000 kg/hm2. 2. With nitrogen fixation of root nodule, rot and decomposing of dry branches and fallen leaves, organic matter, total nitrogen, pH and germ of degrading soil tended to rising after S. guianensis planting and plowing. Increasing root biomass and rhizobium nodules had been repaired and improved microenvironment of soil, especially made an significant increase for germs, in 0-20 cm soil from 0.020 × 105-1.54 × 105 to 1.880 × 105-70 × 105,and 20-40 cm soil from 0.020 × 105-0.380 × 105 to 1.100 × 105-52.5 × 105. 3. S. guianensis, either planting or plowing into soil as green manure planting, could significantly (P < 0.05) improve total nitrogen, organic matter, available phosphorus, available K of degraded soil in the fruit tree canopy drip line.