Soil fertility changes of cultivated land in Eastern China

With the intensified pressure of population increase on natural resources and the environment in China, changes in soil quality, especially in soil fertility, have become the focus of increasing world wide concern The aim of this paper is to try to precisely judge the new changing trend in soil fertility and quality in China for the sake of providing scientific basis for decision making to policy makers Data used in this article is from the second national soil census conducted in 1982 1986 and the follow up soil survey based on the sample plots of the soil census done by Nanjing Institute of Soil Science in 2000 Five soil chemical indicators-organic matter total nitrogen, effective phosphorus, effective potassium, and pH value, with close relation to the crops growth, are selected as the primary analytical variables of soil fertility In this paper, agricultural soil fertility and quality changes from the early 1980s to 2000 were described by using data from 3 regions in China-the Northeast, the North China Plain and the middle and lower reaches of the Yangtze River-covering 180 sample plots in 15 counties of 6 provincesin.The principle for sample plot and data selection in the study is that soil fertility indicators mentioned above should be recorded both in the early 1980s and 2000 on sample plot basis Meanwhile, soil sampling season and analytical methods of soil experiments in the two periods should be basically the same so as to guarantee data from each plot of the two periods one to one correspondence and comparably in agreement. This is one of the reasons accountable for the more reliable and more convincing analysis and conclusions of the present paper than other similar studies The results show that, on average, soil organic matter, total nitrogen and effective phosphorus content have been increased since rural reform in China, although soil effective potassium and pH value degraded From the perspective of spatial distribution, however, there exist significant variations in soil fertility and quality The average soil fertility rose in North China and the middle and lower Yangtze River basin, and dropped in Northeast China Additionally, with the exception of North China, which saw an improvement in soil pH value, acidification tendency was observed in the middle and lower reaches of the Yangtze River and Northeast China.