摘要
The Taihu Region in eastern China is one of China's most intensive agricultural regions and also one of the economically most developed areas. High nitrogen balance surpluses in the summer rice-winter wheat double-cropping systems are leading to large-scale non-point source pollution of aquifers. In an interdisciplinary approach, four-year (1995-1998) field trials were carried out in two representative areas (Jurong County and Wuxi City) of the Taihu Region. Five farmers' field sites were chosen in each of the 2 locations, with each site divided into 'standard' (farmers' practice) and 'reduced' (by 30%-40%) N fertilization. For both fertilization intensities, N balance surpluses and monetary returns from grain sales minus fertilizer expenditures were calculated in an economic assessment. Based on the field trials, the mineral N fertilizer application rates reduced by about 10% for rice and 20%-30% for wheat were recommended in 1999. Since 1999, the research focused on the trends in N fertilizer application rates and changes in grain and agricultural commodities prices.Summer rice N fertilizer use, in Wuxi City as of 2001, dropped by roughly 25%, while for winter wheat it decreased by 10%-20%, compared to the 1995-1998 period. This has been achieved not only by grain policy and price changes, but also by an increased environmental awareness from government officials. Nitrogen balance surpluses in Anzhen Town (of Wuxi City) have consequently diminished by 50%-75% in rice and by up to 40% in wheat, with reductions being achieved without concomitant decreases in physical grain yields or returns from sales minus fertilizer costs.
The Taihu Region in eastern China is one of China's most intensiveagricultural regions and also one of the economically most developed areas. High nitrogen balancesurpluses in the summer rice-winter wheat double-cropping systems are leading to large-scalenon-point source pollution of aquifers. In an interdisciplinary approach, four-year (1995—1998)field trials were carried out in two representative areas (Jurong County and Wuxi City) of the TaihuRegion. Five farmers' field sites were chosen ineach of the 2 locations, with each site dividedinto 'standard' (farmers' practice) and 'reduced' (by 30%-40%) N fertilization. For bothfertilization intensities, N balance surpluses and monetary returns from grain sales minusfertilizer expenditures were calculated in an economic assessment. Based on the field trials, themineral N fertilizer application rates reduced by about 10% for rice and 20%-30% for wheat wererecommended in 1999. Since 1999, the research focused on the trends in N fertilizer applicationrates and changes in grain and agricultural commodities prices. Summer rice N fertilizer use, inWuxi City as of 2001, dropped by roughly 25%, while for winter wheat it decreased by 10%—20%,compared to the 1995—1998 period. This has been achieved not only by grain policy and pricechanges, but also by an increased environmental awareness from government officials. Nitrogenbalance surpluses in Anzhen Town (of Wuxi City) have consequently diminished by 50%—75% in rice andby up to 40% in wheat, with reductions being achieved without concomitant decreases in physicalgrain yields or returns from sales minus fertilizer costs.
基金
Project supported by the Volkswagen-Foundation, Germany (No. Ⅱ/69 948)
the Institute of Soil Science, Chinese Academy of Sciences.
