| The monitoring and analysis of the yield and biomasses of the crops, the soil nutrients, and the yields and nutrient contents of hedge pruning were conducted at different locations of the compound operational system combining traditional slopeland farming and nitrogen-fixing hedge plants in the valleyland area of Jinsha River. The results showed that with the traditional slopeland farming, these items did not significantly differ among different treatments; but in different treatments with hedge plants the biomasses of corn and corn stalks in the lower part of the cropping belts were higher than those in the middle and upper parts of the cropping belts, and the biomasses and economic yields of the crops in the upper part of the cropping belts were lower than those in the middle and lower parts of the cropping belts;The contents of the nutrients in the upper part of the cropping belts were lower than those in the middle and lower parts of the cropping belts. All these showed that the introduction of nitrogen fixing plants into the farming system for slopeland resulted in the differentiations in soil nutrients and crop growth down slopeland. This was because soil erosion partially occurred in the cropping belts of the hedge models, i.e. the soil dislocated in the upper parts of the cropping belts deposited in the lower part of the cropping belts due to the interception of hedge plants, thereby leading to soil deterioration and nutrient enrichment in the lower part of the cropping belts, which were the major factors to initiate the differentiations of the soil nutrients and crop yields at different locations. The hedges took in nitrogen, phosphorous and potassium in deep soil, and returned them into topsoil of the cropping belts through hedge pruning. Such nitrogen-fixing plants as leucaena leucocephala and Tephrosia candida annually absorbed nitrogen 79258 kg/hm2, phosphorous 734 kg/hm2 and potassium 730 kg/hm2; accordingly, the nitrogen and potassium amounts could meet with the amounts required for a normal crop yield and the phosphorous amount were not enough for the normal yield so that phosphorous fertilizers should be applied to the system. |