金沙江干旱河谷坡地复合经营系统内竞争及养分平衡研究

Competition and nutrient balance in the compound operational system for the dry slopeland in the valleyland area of Jinsha River

对干旱河谷传统种植制度下耕地和氮植物篱农林复合经营系统植物篱不同位置的农作物产量、生物量、土壤养分和植物篱枝叶量及其养分含量进行监测和分析。结果表明:传统坡耕地种植方式中各行无显著差异,而植物篱不同处理中,种植带下侧玉米及其秸秆生物量均高于中部和上侧,种植带上侧农作物生物量和经济产量低于种植带下侧。种植带上侧的养分状况也不及种植带中部和下侧,这表明固氮植物篱引入坡耕地系统后坡耕地土壤养分特征和农作物生长状况在顺坡方向发生了分异。这是由于植物篱模式中种植带中仍存在局部土壤侵蚀,种植带上侧侵蚀的土壤由于植物篱的拦截作用在种植带下侧淤积,使上侧土壤恶化而下侧土壤养分相对富集,这是引起表土养分分异和不同位置农作物产量差异的主要因素。植物篱吸收深层土壤的磷、钾,并通过刈割枝叶返还种植带表土。新银合欢、山毛豆等固氮植物篱每年通过枝叶输入种植带的氮、磷、钾、钙、镁分别为79～258kg/hm2、6～21kg/hm2、39～207kg/hm2、7～34kg/hm2、7～30kg/hm2,氮素、钾素可满足农作物一般产量所需,而磷素不足,这表明该系统要使用磷肥。

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 79~258 kg/hm\+2, phosphorous 7~34 kg/hm\+2 and potassium 7~30 kg/hm\+2; 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.