Taihu Lake area is one of the most developed areas in agricultural production. Application of fertilizers and pesticides in large quantities greatly aggravate environmental pollution of this area, and water pollution ...Taihu Lake area is one of the most developed areas in agricultural production. Application of fertilizers and pesticides in large quantities greatly aggravate environmental pollution of this area, and water pollution has worsened to an unbearable condition. Two sampling farms (respectively 1 hm2) under rape-rice rotation and wheat-rice rotation were selected as studied ecosystem and a 5-yr-old Poplar forest and 8-yr-old Metasequoia forest were chosen in the selected areas. By collecting samples of Nitrogen, Phosphorus in water, crops and underground of forest, the transfer and loss of N and P (main water pollutants) in faming ecosystem were studied, and the effects of forest belts on non-point source pollution of agricultural lands was analyzed. The results indicated that the transfer and loss of N and P vary with means of rotation, types of crops and the amount of fertilizer application. Buffering forest belts betweens farmlands and ditches can effectively stop and purify such elements as N and P in soil runoffs, thus controlling non-point source pollution of agricultural lands. When the width ratio of farmland to forest belt is 100 to 40, 50.05% losing N, 29.37% losing P can be absorbed by forest under rape-rice rotation and 30.98% N, 86.73% P can be absorbed by forest under wheat-rice rotation. When the width ratio of farmland to forest belt is 150 to 40, 33.37% losing N, 19.58% losing P can be absorbed by the forest under rape-rice rotation, and under wheat-rice rotation 20.65% lost N and 57.82% lost P can be absorbed. There is only some purification effect when the width ration of farmland to forest belt is 200 to 40. Based on model of buffering forest belts, the width ratio of farmland to forest is determined between 100 to 40 and 150 to 40, because it not only can purify water, but also occupy less farmland. It is suggested that Poplars, with the characteristics of fast-growing and high value, are suitable to be planted as shelter-forest in Taihu Lake Watershed.展开更多
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...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.展开更多
The nitrogen （N） pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system ...The nitrogen （N） pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system （GPS）. The seasonal variations in the concentrations of different N components in the rivers were measured. Using tension-free monolith lysimeters and ^15N-labeled fertilizer, field experiments were carried out in this region to determine variations of iSN abundance of NO3^- in the leachate during the rice and wheat growing seasons, respectively. Results showed that the main source of N pollution of surface waters in the Taihu Lake region was not the N fertilizer applied in the farmland but the urban domestic sewage and rural human and animal excreta directly discharged into the water bodies without treatment. Atmospheric dry and wet N deposition was another evident source of N pollutant of the surface waters. In conclusion, it would not be correct to attribute the N applied to farmlands as the source of N pollution of the surface waters in this region.展开更多
基金This paper was supported by the Environmental Protection Foundation of Jiangsu Province (2000(二) 0009) National Natural Science Foundation of China (NSFC39970605).
文摘Taihu Lake area is one of the most developed areas in agricultural production. Application of fertilizers and pesticides in large quantities greatly aggravate environmental pollution of this area, and water pollution has worsened to an unbearable condition. Two sampling farms (respectively 1 hm2) under rape-rice rotation and wheat-rice rotation were selected as studied ecosystem and a 5-yr-old Poplar forest and 8-yr-old Metasequoia forest were chosen in the selected areas. By collecting samples of Nitrogen, Phosphorus in water, crops and underground of forest, the transfer and loss of N and P (main water pollutants) in faming ecosystem were studied, and the effects of forest belts on non-point source pollution of agricultural lands was analyzed. The results indicated that the transfer and loss of N and P vary with means of rotation, types of crops and the amount of fertilizer application. Buffering forest belts betweens farmlands and ditches can effectively stop and purify such elements as N and P in soil runoffs, thus controlling non-point source pollution of agricultural lands. When the width ratio of farmland to forest belt is 100 to 40, 50.05% losing N, 29.37% losing P can be absorbed by forest under rape-rice rotation and 30.98% N, 86.73% P can be absorbed by forest under wheat-rice rotation. When the width ratio of farmland to forest belt is 150 to 40, 33.37% losing N, 19.58% losing P can be absorbed by the forest under rape-rice rotation, and under wheat-rice rotation 20.65% lost N and 57.82% lost P can be absorbed. There is only some purification effect when the width ration of farmland to forest belt is 200 to 40. Based on model of buffering forest belts, the width ratio of farmland to forest is determined between 100 to 40 and 150 to 40, because it not only can purify water, but also occupy less farmland. It is suggested that Poplars, with the characteristics of fast-growing and high value, are suitable to be planted as shelter-forest in Taihu Lake Watershed.
基金Project supported by the Volkswagen-Foundation, Germany (No. Ⅱ/69 948) the Institute of Soil Science, Chinese Academy of Sciences.
文摘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.
基金Project supported by the State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences (No. 035109)the National Natural Science Foundation of China (No. 30390080).
文摘The nitrogen （N） pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system （GPS）. The seasonal variations in the concentrations of different N components in the rivers were measured. Using tension-free monolith lysimeters and ^15N-labeled fertilizer, field experiments were carried out in this region to determine variations of iSN abundance of NO3^- in the leachate during the rice and wheat growing seasons, respectively. Results showed that the main source of N pollution of surface waters in the Taihu Lake region was not the N fertilizer applied in the farmland but the urban domestic sewage and rural human and animal excreta directly discharged into the water bodies without treatment. Atmospheric dry and wet N deposition was another evident source of N pollutant of the surface waters. In conclusion, it would not be correct to attribute the N applied to farmlands as the source of N pollution of the surface waters in this region.
