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坡耕地是我国西南地区最重要的土地利用类型,也是我国一项重要的国土资源。由于该地区坡耕地石漠化程度高,土壤侵蚀问题严重,致使坡耕地土壤肥力不断退化。以重庆市中梁山坡耕地样区为例,采用模糊综合指数法进行小尺度坡耕地土壤肥力评价。经取样数合理性分析表明,25个样点估计研究区土壤肥力评价能够满足90%置信水平条件下,10%、15%和20%的相对误差取样数的精度要求;运用主成分分析(PCA),通过计算变量的Norm值筛选有机质、全氮、全磷、全钾、碱解氨、耕层厚度和粉黏比进入最小数据集(MDS),并对进入MDS的肥力因子进行相关系数分析检验,表明选取的MDS能最大程度表达坡耕地土壤属性信息;利用隶属度函数实现评价指标量纲归一化并对单项肥力指标进行评价,采用加权求和模型计算土壤肥力综合指数(IFI),结果表明,土壤有机质和全磷是影响研究区土壤肥力的限制因子,研究区80%样地肥力综合指数在0.40~0.60之间,肥力水平处于中等程度。
Slope cultivated land is the most important type of land use in southwest China and is also an important land and resources in China. Due to the high degree of rocky desertification on sloping land in the area, the problem of soil erosion is serious, resulting in the continuous decline of soil fertility on sloping farmland. Taking Zhongliang hillside farmland in Chongqing as an example, the fuzzy comprehensive index method was used to evaluate the soil fertility of small scale sloping farmland. The rationality analysis of sampling number showed that the soil fertility evaluation of 25 sampling sites could meet the precision requirements of 10%, 15% and 20% relative error sampling number under 90% confidence level. The principal component analysis (PCA) ). The Norm value of the variables was used to select the minimum data set (MDS) of organic matter, total nitrogen, total phosphorus, total potassium, alkaline hydrolysis ammonia, topsoil thickness and powder to clay ratio, and the correlation coefficient analysis of the fertility factor into the MDS The results showed that the selected MDS can express the soil attribute information of slope farmland to the maximum extent. The membership function was used to normalize the dimension of evaluation index and evaluate the individual fertility index. The weighted summation model was used to calculate the soil fertility index (IFI) The results showed that soil organic matter and total phosphorus were the limiting factors affecting the soil fertility in the study area. The fertility index of 80% of the sample plots in the study area ranged from 0.40 to 0.60, and the fertility level was moderate.