Temporal And Spatial Variation Of Farmland Soil PH And Analysis In The Factors In Yizheng City

With the increasing acute conflictions between population , resource and environment people gave more and more common attention to soil quality. Soil pH had been given more concern,because it played an important role in soil and enviroment system, it affacted plant growth ,soil nutrient availablity , soil microbial availablity , the quality of agricultural products, etal.The paper attached great emphasis on Spatial and Temporal Variation in soil pH in Yizheng city in Jiangsu province, finding out main driving forces and proposing some management measures.The datas were analysed through conventional statistical and GIS . By research, the results were as follows:1. From 1980 to 2005 , soil pH showed a gradual downward trend in Yizheng city, and the rate of decline got faster and faster. From 1980 to 1994, soil pH average decreased from 6.62 to 6.43, with an average annual decline in 0.013 pH units. From 1994 to 2005 ,soil pH decreased to 6.17 from 6.43, 0.022 pH units at an average annual rate of decline. The rate of decline after 12 years was significantly higher than the previous 15 years.2.The value of Soil pH under different soil types showed that: gray tide soil> paddy soil> yellow-brown soil> rocky soil.3. The value of Soil pH under different land-use types showed that: the value of Dryland soil pH was higher than the soil of paddy fields, but soil pH values decreased significantly faster than that of paddy fields.4. The trend effect analysis of Kriging interpolation of soil pH values in 1984, 1994, 2005 and the level distribution pattern of soil pH values of different years suppo-rted by GIS showed that 60% of the city soil pH value was from5.0 to 6.5 ,it meaned the soil was weak acid, and the distribution of soil pH values was in general gradually increasing from northwest to southeast.5. The result of spatial and temporal variation of soil pH analysed by spatial overlay at different stages further explained the changes of soil pH in the past 20 years,which provided a scientific basis for agricultural management. In the whole, , the soil pH value of Yizheng City was decreasing year by year; the decrease in soil pH values from 1994 to 2005 was faster than that from 1980 to1994; the soil pH value of the whole city was decreasing year by year,but it was increasing in some areas,for example in Dayi town and Liuji town.It may be related to the destruction of the farmland surface caused by land reclamation, the overed immature soil, and the alkaline construction waste.From the survey of the different fertilizers form of 182 farmers in Yizheng Soil and Fertilizer Station in 2003, the farming system, fertilizer conditions, food production and farmers production at different stages from1980 to 2006, the monitoring results of soil fertility in arable land in long-term monitoring points from1988 to 2005,and the data of rainfall from the Environmental Protection Agency of Yizheng City from 1996 to 2005 ,we summed up the main driving factors for the changes of soil pH: the decrease of organic fertilizer application, long-term use of a large number of physiological acid fertilizers, acid rain, land use and field management.