基于模糊c-均值聚类的亚热带丘陵区土壤肥力空间分异与管理分区OA北大核心CSTPCD

[Objectives]Our study focused on understanding the spatial variation of soil fertility in subtropical hilly region with complex terrain,and aimed to approach an effective way for regional nutrient management in hilly regions.[Methods]A case study was carried out in a typical watershed,Jinjing Town,Changsha County,Hunan Province,which belongs to subtropical hilly region.A total of 946 soil samples were collected within the study area of 112 km²in 2009.The tested soil fertility indicators included soil organic carbon(SOC),total nitrogen(TN),total phosphorus(TP),available nitrogen(AN),available phosphorus(AP),and pH.Geographical statistics and fuzzy c-means clustering algorithm were used to analyze the spatial heterogeneity of soil fertility.Principal component analysis was employed to divide the watershed into different fertility zones.The results were validated using significance test of difference and coefficient of variation.[Results]Except for soil pH,SOC,TN,TP,AN and AP exhibited moderate to strong degree of spatial variations,with the coefficient of variation(CV)ranging from 36%to 125%.The study area was then divided into three soil fertility zones(MZ1,MZ2 and MZ3)based on principal component analysis and fuzzy c-means clustering algorithm.The CV values of soil fertility indices after zoning were distinctively reduced,the lowest and highest reduction were in the CV of pH and AP,with the zoning CV reduction of 6%and 96%,respectively.Soil fertility indices tended to be homogeneous within a zone,but more heterogeneous among zones(P<0.01).The late rice yields and total yields of early and late rice were significantly higher in zone MZ1 than in MZ2 and MZ3.In the three zones,soil pH was 4.12,4.04 and 4.00,respectively,all of which were at acidic levels.SOC contents were at a high level(15.15,14.38,and 12.24 g/kg).TN contents were at a high level(1.56,1.48,and 1.34 g/kg).TP contents were at high to very high level(0.86,0.69,and 0.60 g/kg).AN contents were at a low level(41.08,35.33,and 26.16 mg/kg).AP contents were at a middle or low level(8.63,4.46,and 3.39 mg/kg).[Conclusions]Soil fertility exhibites significantly spatial variations in the subtropical hilly region due to the complex topography.Zoning based on the soil fertility is an effective way to eliminate the heterogeneity and propose regional nutrient management strategies.The watershed of the case study is divided into three fertility zones,the MZ1,MZ2,and MZ3 zones should focus on ameliorating soil acidification,enhancing the utilization efficiency of fertilizer nitrogen,and avoiding the over-application of chemical nitrogen fertilizers.For zone MZ1,a moderate reduction in the application of inorganic phosphorus fertilizers was recommended,with particular attention to preventing excessive phosphorus fertilization during critical growth stages.MZ2 and MZ3 zones should consider appropriate application of biological enzyme-activated phosphate fertilizer or increasing application of organic fertilizers to enhance the utilization efficiency of phosphorus by crops.