Studies On The Spatial And Temporal Distribution And Information System Of Soil Potential Acid In Cropland Of Fujian Province

Soil potential acid?PA?is one of the potential factors limiting plant growth,and also an important base in soil acidity regulation.The potential acid and pH value of surface soil samples of cultivated lands in Fujian Province were proportionally selected and measured,and then optimized relational model between soil pH and potential acid value was fitted.The 1:50 000 databases of cropland soil potential acid in 1983,2009 and 2016 were established by using the topsoil pH data of 36777,236445 and 21269 sampling sites collected in 1983,2009 and 2016respectively.The dynamics of cropland soil potential acid in Fujian Province and its driving factors were explored by the integrative method of GIS and grey slope correlation analysis and information system was developed.The results showed that:1.The cropland soil potential acid value had an overall upward trend in Fujian Province from 1983 to 2016.Compared with 1983,the average value of soil potential acid?PA?in 2009 and 2016 increased 1.08cmol·kg^-11 and 1.25 cmol·kg^-1,respectively.The increase rate from 1983to 2009 was 0.02 cmol·kg^-1·yr^-11 higher than that from 2009 to 2016.2.Meanwhile,there were significant spatial differences in cropland soil potential acid change around the province from 1983 to 2016.The maximum and minimum change of cropland soil potential acid were located in Longyan and Sanming city,respectively,the difference between them was more than 4 times.In terms of land use type,the cropland soil potential acid change from the largest to the smallest were paddy field>irrigated land>upland;acidic sulfate paddy soils,gleyed paddy soils and submergenic paddy soils had the largest change and were one time higher than the average change around the province,while the latosolic red earths and salinized paddy soils had the smallest change,which were 25.68%and 28.38%of the average,respectively;the minimum soil potential acid change was under an elevation of 200 m,and other areas increased first and then decrease gradually with elevation.3.From the point of view of cropland acid zoning,the cropland acid zoning in 1983-2009 and 2009-2016 were mainly mild acidification zoning,while the cropland acid zoning in the whole province was mainly distributed in Zhangzhou City in southern Fujian,western Quanzhou City,Longyan City in western Fujian and Nanping City in northern Fujian.Compared with 1983-2009,the area of mild acidification zone,moderate acidification zone and severe acidification zone decreased by3.22%,72.81%and 93.04%from 2009 to 2016,respectively.4.Grey slope correlation analysis showed that the driving factors of dynamic changes of cropland soil potential acid included the application rates of nitrogenandphosphorusfertilizer,cationexchange capacity?CEC?,clay content,pH and silt content,the grey slope correlation of them were>0.96.Accordingly,it would be an effective approach to slow down the increase of cropland soil potential acid in Fujian Province to optimize fertilization management and apply alkaline ameliorant scientifically.5.The amount of lime application per unit area and the total amount of lime application in the whole province were 3.96×10³ kg·hm^-22 and5302.37×10⁶ kg,respectively.The spatial difference was showing a decreasing trend along northwest to southeast.The theoretical application area of lime was mainly low lime application area,accounting for 56.24%of cultivated land in Fujian Province.And the medium and high lime application areas mainly distributed in northwest and south of Fujian.6.The information system of cropland acidification in Fujian Province was supported by WebGIS,which established uniform standard and unified management system for the whole province.The system helped users grasp basic data of soil acidification of cultivated land units in Fujian Province and provided plan of lime application according to different acidification degree.Meanwhile,the system provided four functions of information navigation,information query,data statistics and system maintenance,which can realize the rational utilization and resource sharing of the big data of cultivated land in Fujian Province.