农业活动与岩溶山区土地利用的可持续性探讨

Agriculture Activity and Sustainable Use of Farmland in Karst Mountain Area

以 4项专题研究及抽样调查为主要资料来源 ,对西南岩溶山区的土地利用进行研究。结果表明 ,由于该区土地土层薄且通透性强和母岩漏水 ,长期耕种后土壤肥力明显下降、粮食产量对化肥的依赖性增强。长期施化肥的土地耕种约 6 0年后 ,土壤有机质含量相当于天然状态下的 30 %。垦殖率在 2 0 %～ 30 %、覆被率在 35 %～ 45 %时粮食产量高而稳定。土层厚度 <5 0～ 80cm、地形坡度 >16°时的梯地对水肥保持及旱情缓解的作用甚小 ,不是解决干旱的途径。该区耕地的持续利用须建立在适当的垦殖率、森林覆盖率及合理施肥基础上。实现该目标的关键是建立生态农业体系 ,缩小耕地面积、减少人口是发展生态农业的前提。

According to case study and sampling,this thesis researches farmland use in southwest China karst mountain area.The results show that because of the soil layer being too thin and freely aerated as well as waterleakage of the parent layer,the soil fertility reduces distinctly,drought and other natural disasters become more serious,yields strongly depend on chemical fertilizer after long-term improper reclamation and cultivation.On condition that large quantity of chemical fertilizer application,the farmland only keeps about 30% organic matter after about 60 years' cultivation in contrast with the uncultivated land.The yields are highest and very stable whene the rate of reclaimed land is about 20% to 30% and the percentage of forest cover is about 35% to 45%.If the gradient of the original land is steeper than 16° and the soil layer is about 50-80cm thick or thinner,the effect to keep soil water and nutrient by building terraced fields can only relief drought slightly and is not at all the effective way to solve karst drought.Through comprehensive analysis,it is considered that sustainable use of calcic farmland in karst mountain must be based firstly on proper rate of reclaimed land;secondly on proper percentage of forest cover;thirdly on reasonable fertilizer application and lastly on effective soil conservation.The key to realize this aim is to establish eco agricultural system.And the prerequisite for that is to reduce the farm land acreage and population in the area.