重庆市丰都县紫色土养分空间变异及土壤肥力评价

综合运用地统计学、GIS和模糊数学相结合的方法,分析了丰都县紫色土养分的空间变异规律,对其土壤肥力进行综合评价,并绘制了养分空间分布图和土壤综合肥力指数空间分布图,为该县紫色土养分分区管理及精准施肥决策等提供理论依据。结果表明:研究区内5种肥力指标中,除有效磷属于强变异性外,pH、有机质、碱解氮和速效钾均具有中等变异性。土壤pH、速效钾的最适模型是指数模型,块金值与基台值之比分别为17.07%和10.65%,有较强的空间相关性;用线性模型可较好地模拟有机质、碱解氮和有效磷,块金值与基台值之比分别为76.37%、84.21%和87.92%,空间相关性较弱。土壤pH、有机质、碱解氮、有效磷和速效钾的变程分别为5.43、28.02、31.24、36.48和2.28 km。土壤pH在长江以北较高与较低区域都呈带状并相间分布,在长江以南呈西低东高状态;有机质、碱解氮、有效磷及速效钾的分布存在明显的方向不均匀性,都呈零星斑状。丰都县土壤肥力质量呈现北低南高的趋势,5个等级地块分别占8.14%、18.86%、31.75%、28.58%、12.67%。丰都县土壤肥力总体水平中等偏上,这主要与该地区地形地质有关,同时也受到社会经济与人为管理措施的影响。

Spatial Variability of Soil Nutrients and Assessment on fertility of Purple Soil in Fengdu City of Chongqing

The spatial variability of soil nutrients of purple soil in Fengdu City of Chongqing was comprehensively analyzed by geostatistics, GIS platform and fuzzy mathematics method. Scatter diagrams of the spatial distribution of soil nutrients were then quantitatively constructed on order to potentially provides theoretical bases not only for the use of management zones (MZs) with purple soil in Fengdu, but also for decision-making inprecision fertilization. The results showed that moderate level of spatial variability occurred in 4 nutrients contents in the research region except available P(AP) which belonged to the strong level. The nugget/still ratios were 17.07% for pH and 10.65% for available K (AK), respectively, which showed strong spatial correlation, and could be modeled with the exponential model. While the nugget/still ratios were 76.37%, 84.21% and 87.92% for organic matter (SOM), available N (AN) and available P (AP), respectively, which showed weak spatial correlation, and could be well modeled with the spherical model. The ranges of pH, SOM, AN, AP and AK were 5.43, 28.02, 31.24, 36.48 and 2.28 km, respectively. pH showed banding distribution both in the higher and lower regions in the north of the Yangtze River, but showed high in the west region and low in the south region in the south of the Yangtze River; all the distribution of SOM, AN, AP and AK showed apparent direction inhomogeneity and were sporadic and patchy. The soil fertility quality of Fengdu decreased from south to north, but generally was above the middle level, the areas of the five grades of fertility quality were 8.14%, 18.86%, 31.75%, 28.58% and 12.67% of the total area, respectively. The fertility quality of Fengdu was affected by soil texture, socio-economic and artificial cultivation management.