我国水蚀区坡耕地土壤肥力现状分析

Present Condition Analysis of Sloping Farmland Soil Fertility in the Water Erosion Zone of China

土壤肥力是土壤质量的重要组成部分,为探讨我国东部水蚀区坡耕地土壤肥力质量现状,以田块尺度为研究单元,选取36个采样点,测定11项土壤养分及肥力环境指标。应用主成分分析法,计算变量的Norm值,结合指标间的相关系数,确定有机质、全钾、pH值、CEC、粘粒含量进入土壤肥力评价的最小数据集（MDS）。采用＂S＂型或抛物线型隶属度函数计算指标隶属度并对单项肥力指标进行评价,利用综合指数模型计算各点土壤肥力综合指数（IFI）进行评价。结果表明：（1）CEC和粘粒含量隶属度值较低,是制约我国水蚀区坡耕地土壤肥力的重要因素;（2）各采样点土壤肥力综合指数变幅是0.17~0.72,平均值为0.44±0.15,属中等肥力水平。36个采样点土壤肥力综合指数等级属低、中、高的比例分别为27.8%,58.3%,13.9%,大多数采样点土壤肥力处于中等及以下水平;（3）6个水蚀二级分区的土壤肥力综合指数均值不存在显著差异,东北低山丘陵和漫岗丘陵区土壤肥力综合指数最高,而西北黄土高原区土壤肥力综合指数最低。研究结果对指导我国水蚀区坡耕地合理施肥和土地资源可持续利用具有重要意义。

Soil fertility was an important component of soil quality.In order to investigate the present statue of sloping farmland soil fertility in the water erosion zone of China,selecting field scale as the research unit,soil samples from the soil layer of 0-20 cm were collected and we tested 11 soil physical and chemical indicators for 36 sampling sites.The principal component analysis（PCA）combined with Norm values and correlation coefficients between the 11 indicators were employed to select the key indexes for representing soil fertility.The key indexes were soil organic matter,total kalium,pH value,cation exchange capacity and clay content.S-type and parabola-type membership functions were used to transform the indicators into dimensionless dates and to evaluate single indicators.Comprehensive index model was used to calculate integrated fertility index（IFI）for each sampling point,providing the basis for quantitative analysis of sloping farmland soil fertility in the water erosion zone of China.The results showed that：（1）The values of membership functions of the indexes revealed that the CEC and clay were the major limiting factors for this region.（2）The IFI for water erosion zone of China varied from 0.17 to 0.72,and the mean value was 0.44±0.15,belonging to moderate fertility level.The proportions of integrated fertility index ranked as low,middle,high level were 27.8%,58.3%and 13.9%of the total area of sloping farmland,respectively.（3）There was no significant difference about integrated fertility indexes between the six secondary partition regions.The IFI of the northeast low mountain and rolling hill region was the highest,while the IFI of the Loess Plateau region wasthe lowest.The results of the study had guiding significance for rational fertilization and sustainable utilization of land resources for sloping farmland in the water erosion zone of China.