Study On The Acidification Of Cropland Soil In Fujian By GIS Technology

In this study,taking Fujian province as the study area,the acidification degree,discrepancy,temporal and spatial variation and it's causes under different regions,soil types and land uses over last 26 years were analyzed deeply with the help of GIS and mathematical model of integrated technology,utilizing the data of Second Soil Census,present land-use survey,soil testing and fertilizer recommendation,precipitation pH monitoring and measured values of 29945 sampling points at 1983 and 236445 sampling points at 2009.Further more,some controlling measures were proposed.The main research conclusions are as follows:1.The soil acidity of cropland in 1983 and 2009 of Fujian both decreased gradually from the northwest to the southeast paralleling to the coastline.Large spatial variability was also observed,with the pH values of 1983 ranging from 3.84 to 8.17 and pH values of 2009 from 3.59 to 8.19,and the area-weighted average of soil pH were 5.51 ±0.45 and 5.22 ± 0.52 respectively,and the coefficient of variation also incresed from 8.17%to 9.96%over past 26 years.Overall the pH values of Fujian decreased about 0.29 units averagely,and the total area of acidification soil accounted for 66.47%of the cropland in Fujian,indicating that the acidification of cropland was obvious.2.Acidification of farmland soil was observed in all regions of Fujian,but the degree and area of acidification differed.The degree of acidification was found to be in the order of:Quanzhou>Nanping>Longyan>Fuzhou>Xiamen>Sanming>Putian>Zhangzhou>Ningde,and the pH value of soil in quanzhou decreased about 0.42 units averagely;the area of acidification was found to be in the order of:Nanping>Sanming>Fuzhou>Longyan>Ningde>Quanzhou>Zhangzhou>Putian>Xiamen,and the area of acidification of Nanping accounted for 21.77%of the acidification soil in Fujian.3.Except Fluvo-aquic soils,the pH values of all soils decreased in varying degree,of which the Coastal solonchaks and Aeolian soils decreased apparently,while Yellow earths declined little over past 26 years.In addition,the pH of Submergenic paddy soils,Acid sulfate paddy soils and Greyfluvo-aquic soils increased slightly,inverse,the pH of other Soil subgroup declined between 0.02 to 0.48 units in 2009 compared to 1983;the pH of Cultivated sandy mud soil,Red sandy mud field.Sandy mud field,Sulfonic acid soils,Cultivated grey sandy soil,Lateritic field and Grey sandy mud field increased between 0.05 to 0.27 units,while the othersoil genus's pH decreased in varying degrees,of which Dark red soils declined the most with an average reduction of 0.65 units.Acidification of soil exist in all the land uses,of which the pH of Irrigated land and Paddy field reduced by 0.30 and 0.20 units respectively.4.The result of the Gray slope-correlation analysis showed that:the influence degree of acidification was found to be in the order of:CEC>clay>Available phosphorus>average pH of rainfall>average annual rainfall>available nitrogen>som>sand>average annual temperature>average annual amount of phosphate fertilizer>elevation>slope>average annual amount of nitrogen fertilizer>silt>average annual amount of potash fertilizer,of which CEC,clay,som,average pH of rainfall,elevation,slop and silt had positive influence on soil acidification and other factors had negative influence.5.Over past 26 years,the area of the degree of strong,moderate and weak acidification soil accounted for 5.49%,23.95%and 37.03%of total cropland soil in Fujian Province respectively,in which the strong acidification of cropland mainly distributed in Changting,Anxi,Liancheng,the moderate acidification of cropland mainly located in Pucheng and Jianou,and the weak acidification of cropland mainly distributed in Jianyang,Jianou,Gutian and Wuping;Paddy soils,Percogenic paddy soils,Yellow mud field and Yellow sandy mud field had the largest area of all degree of acidification;The area of acidificatinog in Irrigated land was larger than the other land use types.Hence,the future cropland fertilizer management of Fujian province should control the amount of fertilizer based on the accuracy nutrient demand and actual acidification,and modulate fertilizer structure in order to amend acidification soil.