[Temporal characteristics of soil fertility of cropland requisition-compensation in the typical region of Yangtze River Delta, China.].

Based on the satellite image in 1984, 2000 and 2016, we analyzed the temporal and spatial variation of cropland requisition-compensation in Changshu City, Jiangsu Province. Based on ArcGIS and the data of soil samples, membership function with integrated fertility index were used to evaluate the soil fertility in 1984 and 2000, respectively. The overlay analysis had been used to reveal the characteristics of soil fertility of cropland requisition-compensation between the period of 1984 to 2000 and 2000 to 2016. Results showed that the cropland reduced by 1/3 from 1984 to 2016, which was occupied by water area (51.7%) and residential, industrial and mining land (41.4%) between 1984 to 2000, while between 2000 to 2016 cropland was occupied dominantly by residential, industrial and mining land (80.8%). The soil fertility of in 65.5% of the total area of Changshu increased while the decreasing part just accounted for 3.9% from 1984 to 2000. At the same time, soil fertility was higher in the south area of Changshu City than other area. The quantity and quality of cropland requisition-compensation were not balanced, with the serious status of occupying more cropland but replenishing less, occupying fertile cropland and replenishing poor one in former period, and occupying more cropland and replenishing less, occupying poor cropland and replenishing poor one in the later period. The trend of cropland shrinking had not been altered, and the cropland compensation in different places was epidemic. The quality of cropland compensation in different places and the temporal characteristic of soil fertility should be highlighted for the balance of cropland requisition-compensation.