| Agricultural nonpoint source pollution is an important reason for water eutrophication, clarifying nitrogen and phosphorous loss from different source such as cropland and poultry farm is the effective base of controlling eutrophication. Jiaxing city is in lowland plain areas with crisscross network of river courses, and so the loss of N and P from cropland and poultry farm is affected strongly by the surrounding hydrology, which makes it very difficult to get significative result through small-scale investigation. In order to make clear of the characteristics of N and P loss from the three land use types, i.e. paddy-upland rotation field, intensive cropping field and poultry farm, we selected 7 representative experimental sites and monitored 14 times on square kilometer scale from July 2006 to June 2007, including 1 site paddy-upland field (flood season 2 times, non-flood season 1 time), 3 sites intensive cropping fields (flood season 1~2 times, non-flood season 1 time), and 3 sites poultry farm (flood season 1 time). Altogether, we monitored and calculated water quality of 5 different type: river water, channel water, soil surface water, channel sediment water, and topsoil water. We have also monitored total nitrogen, water soluble nitrogen, nitrate, and ammonium of river water, channel water and soil surface water. For channel sediment, we monitored water extractable P (WEP), Olsen P, nitrate, and ammonium nitrogen. For cropland soil, we monitored WEP and Olsen P of 0~5 cm topsoil, and mineral nitrogen (nitrate and ammonium N) of 0~20 cm topsoil. The main conclusions are as follows:The total water storage ranged from 83.7 to 944.7×103m3/km2, with an average of 200.3×103m3/km2 .The maximum of water storage was 11.3 times of that of the minmum. The average of the total water storage in four farmland study areas in the flood season and the non-flood season was 198.7×103m3/km2 (83.7~276.0×103m3/km2), 174.9×103m3/km2 (83.7~276.0×103m3/km2) respectively. The total water storage in four farmland study areas in the flood season was 1.1 times of that in the non-flood season. It was obvious that the average of the total water storage had little difference between in flood season and non-flood season. The water in rivers, ditch, soil surface water of paddy field, 0~20 cm and 0~5 cm soil layer averagely were respectively 69.6%, 0.9%, 2.0%, 27.5%, 7.7% of the total water storage. The river water was the main part, and 0~20 cm soil layer took second place. So the water in rivers and 0~20 cm soil layer were the main factor on the differentiation of the total water storage among the different study areas.The total P storage ranged from 177 to 6220 kg/km2, with a mean of 933 kg/km2. The maximum of total P storage was 53 times of that of the minmum.The total P storage in poultry farm (760 kg/km2) and intensive field (1111 kg/km2) was respectively 4.4, 6.5 times of that in paddy-upland rotation field (172 kg/km2).Proportion of the total P of river water, ditch water, soil surface water, WEP of sediment of ditch (0~5 cm) and soil layer (0~5 cm) for the total P storage were respectively 10.5%, 0.4%, 0.3%, 0.1%, 88.7%. The WEP of soil layer (0~5 cm) was the main existence form of the total P storage. Among the seven study areas, the average storage of the WEP of soil layer (0~5 cm) of farmland was 958 kg/km2, varing in the range of 0~6167 kg/km2. The WEP of soil layer (0~5 cm) of the farmland in poultry farm and intensive field was 270, 1038 kg/km2 respectively and were both higher than paddy-upland rotation field(26 kg/km2). The concentration of them was 40.51, 29.87 mg/kg, higher than paddy-upland rotation field (0.79 mg/kg). The storage of the WEP of soil layer (0~5 cm) of farmland was affected by the concentration and the total area of farm. Therefore, the storage of the WEP of soil layer (0~5 cm) of the farmland in poultry farm was less than in the intensive field because of its smaller farmland area, although its concentration of the WEP of soil layer (0~5 cm) was the highest in the three kinds of study areas.The order of the concentration of the total P in river water was: poultry farm> intensive field > paddy-upland rotation field. The WEP concentration of sediment of ditch and the total P concentration of ditch water were of the same order.The total P storage of four farmland study areas and river water, ditch water, soil surface water, the WEP of sediment of ditch (0~5 cm) and soil layer (0~5 cm) in the flood season were 1.5, 2.2, 2.1, 1.2, 1.4, 1.5 times of that in the non-flood season respectively.The total storage of N in seven study areas was 14477 kg/km2, varing in the range of 3480~51555 kg/km2. The maximum of total storage of N was 14.8 times of that of the minmum. The total storage of N in poultry farm, intensive field and paddy-upland rotation field study areas was respectively 3913, 17082, 5596 kg/km2. Proportion of the the storage of total N of river water, ditch water, soil surface water, Nmin of sediment of ditch (0~5 cm) and soil layer (0~20 cm) was respectively 5.7%, 0.2%, 0.2%, 0.2%, 93.8% of the total storage of N. The Nmin storage of soil layer (0~20 cm) was the main existence form of the total storage of N. The average Nmin of farm soil layer (0~20 cm) in seven study areas was 13576 kg/km2, varing in the range of 0~50900 kg/km2.The average Nmin of soil layer (0~20 cm) in poultry farm, intensive farm and paddy-upland rotation field study areas was 1143, 16309, 4635 kg/km2 respectively.The concentration of them was respectively 43.0, 117.3, 33.9 mg/kg. Although the difference of the Nmin of soil (0~20 cm) between paddy-upland rotation field and poultry farm was not great, the storage of soil N in poultry farm was less than the paddy-upland rotation field because of the farmland area.The difference of the total storage of N, storage of TN in river water, storage of Nmin in sediment of ditch (0~5 cm) and soil layer (0~20 cm) between in flood season and non-flood season was not great, but storage of TN in ditch water in flood season was 1.7 times of that in the non-flood season.
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