Study On Spatial Acidification Variation And It's Impacting Factors Of Cropland Soil

Soil pH is an important indicator of soil fertility of cropland soils,and soil acidification,a representation of the decline of soil pH value,is a vital problem in soils of intensive agricultural systems in China.As we all know,crop growth and improvement of ecological environment were heavily obstructed by soil acidification.Thus,accurate revelation of acidification degree and causes of regional cropland soils is of great significance for enhancement of cropland soils quality and sustainable development of agriculture.In this study,with the aid of the ArcGIS software and the Grey slope correlation analysis model,based on the data of topsoil attributes collected from 36 777 sampling sites during the second soil survey in 1982 and 236445 sampling sites in extrapolation of soil surfaces of soil testing and fertilizer recommendation in 2008,and the data of fertilizer,average annual temperature and average annual precipitation of the past 26 years of Fujian Province,a 1:50 000 mapping scaled cropland soil pH and relevant attribute database of the province was established.This database,containing a total of 612426 patches,was used to study acidification degree.And with the aid of the SEM and the Grey slope correlation analysis model,exploring the causes of cropland acidification of Fujian province in the past 26 years,in order to provide scientific basis of soil acidification regulation.The results showed that:1.The average value of soil pH were 5.38 and 5.11 of 1982 and 2008 year respectively in Fujian Province.And the soil pH of eastern region farmland is higher than west,which indicating the spatial variation of cropland pH wree very obviously.The average value of soil pH had decreased by 0.27 units in the past 26 years in Fujian province,which indicating that the acidification of croplands was obvious.2.Analysis on climatic zone scale,the results showed that acidification areas of mid-subtropical and south-subtropical accounted for 44.26%and 26.74%of the total croplands areas of the whole province.The acidification areas of one-crop system,two-crop system and three-crop system accounting for 4.02%,44.64%and 51.34%.The acidification areas of plain region,valley basin and hilly region accounted for 56.71%,74.86%and 75.83%.And the acidificationareas of<200 m,200?400 m,400-600 m,600?800 m,800?1000 m,1000?1200 m and 1200?1400m accounted for 61.60%,74.16%,81.27%,76.54%,72.09%and 64.67%of the total farmlands soil areas.The of acidification areas of different interval of road accounted for 67.99%,79.38%,82.62%,79.10%,82.98%and 82.84%of the total farmlands soil areas.The acidification areas of different interval of resideations accounted for 67.60%,75.48%,78.73%,78.15%,78.73%and 69.42%of the total acidification farmlands of Fujian Province.3.Total acidified areas accounted for 71.00%of the whole croplands of Fujian province in the past 26 years.The low acidified croplands were widely disperse Fujian province and its areas accounted for 42.78%and 60.26%of total farmland soil of the whole province and total acidification farmland soil.Areas of moderately and strongly acidified croplands accounted for 21.53%,6.68%and 30.33%,9.41%of total farmland soil of the whole province and total acidification farmland soil.4.Grey slope correlation and SEM analysis suggested that serious acid rain,high precipitation and high fertilizer input were the main factors contributing to the acidification of croplands in Fujian Province.And their direct effects?indirect effects and total effects are-0.70,-0.16 and-0.86,-0.4,-0.35 and-0.75,0.38,0.11 and 0.49.It is effective approach for controlling cropland soil acidification in Fujian Province to strictly control the emission of industry acidic exhaust gas containing sulfur in order to reduce acid rain and to carry out optimal fertilizer management programs by increasing organic fertilizer and reducing nitrogen and phosphorus fertilizer.