Excess phosphorus （P） from agricultural soils contributes to eutrophication in water bodies. Samples （n = 60） were taken from sites where rice paddies have been converted to vegetable fields for 0, 〈 10, 10-20, a...Excess phosphorus （P） from agricultural soils contributes to eutrophication in water bodies. Samples （n = 60） were taken from sites where rice paddies have been converted to vegetable fields for 0, 〈 10, 10-20, and 〉 20 years and analyzed for five inorganic P （Pi） fractions, three organic P （Po） fractions, and several soil parameters to investigate how land use conversion affects Pi and Po fractions in a peri-urban area of China with soils characteristic of many agricultural areas of Asia. Significant increases of 33, 281, 293, and 438 mg kg-i were found for soluble and loosely bound Pi （SL-Pi）, aluminum-bound Pi （Al-Pi）, calcium-bound Pi （Ca-Pi）, and iron-bound Pi （Fe-Pi）, respectively, after conversion from rice paddies to vegetable fields. Most of the increase in Pi was in the form of Fe-Pi, which increased from 8% of total P （TP） on paddy soil to 31% on the soil with 〉 20-year vegetable cultivation, followed by Al-Pi, which increased from 2% to 19% of TP. For Po fractions, there was no significant change in P concentrations. The conversion of land use from paddy fields to high intensity vegetable fields was causing significant changes in soil P fractious. Management practices were causing a buildup of soil P, primarily in the Fe-Pi fraction, followed by Ca-Pi and Al-Pi fractions. If current trends continue, a 30%-70% increase in TP could be expected in the next 20 years. Farmers in the area should reduce P application and use to maximize P uptake.展开更多
We investigated the patterns of phosphorus transport from purple-soil cropland of 5° and 10° slopes with bare and vegetated surfaces,respectively.Each type of land was tested under a simulated moderate rainf...We investigated the patterns of phosphorus transport from purple-soil cropland of 5° and 10° slopes with bare and vegetated surfaces,respectively.Each type of land was tested under a simulated moderate rainfall of 0.33 mm/min,a downfall of 0.90 mm/min,and a rainstorm of 1.86 mm/min.Runoff dynamics and changes in the export amount of phosphorus are influenced by the rainfall intensity,the slope and surface conditions of cropland.The vegetation diverts rain water from the surface into soil and helps the formation of a subsurface runoff,but has little influence on runoff process at the same sloping degree.Vegetated soil has a smaller phosphorous loss,particularly much less in the particulate form.A heavier rainfall flushes away more phosphorous.Rainwater percolating soil carries more dissolved phosphorous than particulate phosphorous.Understanding the patterns of phosphorous transport under various conditions from purple soil in the middle of Sichuan basin is helpful for developing countermeasures against non-point-source pollution resulting in the eutrophication of water bodies in this region that could,if not controlled properly,deteriorate the water quality of the Three Gorges Reservoir.展开更多
Soils from urban and suburban areas are normally enriched with phosphorus (P). Sixteen urban soils with a wide range of total P concentrations under typical urban land uses were sampled and analyzed for extractable P ...Soils from urban and suburban areas are normally enriched with phosphorus (P). Sixteen urban soils with a wide range of total P concentrations under typical urban land uses were sampled and analyzed for extractable P concentrations using water, sodium bicarbonate and citric acid. Meanwhile the soils were artificially leached in columns and P concentrations in the leachates were determined. With linear regression a two-stage linear relationship was found to exist between concentrations of P in the leachates …展开更多
Phytochemical constituents of the shoots and roots extract of chosen eight medicinal plants （Plantago major, Verbesina encelioides, Glinus lotoides, Helotropium supinum, Mentha microphylla, Euphorbia hirta, Juncus su...Phytochemical constituents of the shoots and roots extract of chosen eight medicinal plants （Plantago major, Verbesina encelioides, Glinus lotoides, Helotropium supinum, Mentha microphylla, Euphorbia hirta, Juncus subulatus and Convolvulus arvensis） were estimated using standard qualitative analysis. The extract contained alkaloids, glycosides, saponins, phenols, tannins, f[avonoids and terpenoids in some medicinal plants while others contain some only of these phytochemical components. Allelopathic effect of the various concentrations of the extracts on the soil algal diversity was also investigated. Wollea saccata was the only algal species disappeared from all applied investigated plant extracts. Phormidium richardsii, Monoraphidium braunii, Eunotia verneris and Nitzschia bilobata were the highly sensitive algal species to all applied shoot and root extract from all tested plants, they disappeared from most of the studied plants. On the other hand, Phormidium animale and Chlorella neustonice were highly tolerant algal species to all applied extracts. Counts of Cyanophyceae, Chlorophyceae and Bacillariophyceae were decreased by addition of some investigated medicinal plants extracts such as Juncus subulatus, Convolvulus arvensis and Euphorbia hirta. So the authors can use these plants extracts in biocontrol of the nuisance of algal bloom or any other microorganisms. Also, these plants may be useful to recover eutrophic water which needs further investigation.展开更多
基金Project supported by the National Science & Technology Pillar Program of China during the Eleventh Five-Year Plan Period (No. 2008BADA7B02)the National Natural Science Foundation of China (No. 40773075)the Natural Science Foundation of Jiangsu Province,China (No. BK2007262)
文摘Excess phosphorus （P） from agricultural soils contributes to eutrophication in water bodies. Samples （n = 60） were taken from sites where rice paddies have been converted to vegetable fields for 0, 〈 10, 10-20, and 〉 20 years and analyzed for five inorganic P （Pi） fractions, three organic P （Po） fractions, and several soil parameters to investigate how land use conversion affects Pi and Po fractions in a peri-urban area of China with soils characteristic of many agricultural areas of Asia. Significant increases of 33, 281, 293, and 438 mg kg-i were found for soluble and loosely bound Pi （SL-Pi）, aluminum-bound Pi （Al-Pi）, calcium-bound Pi （Ca-Pi）, and iron-bound Pi （Fe-Pi）, respectively, after conversion from rice paddies to vegetable fields. Most of the increase in Pi was in the form of Fe-Pi, which increased from 8% of total P （TP） on paddy soil to 31% on the soil with 〉 20-year vegetable cultivation, followed by Al-Pi, which increased from 2% to 19% of TP. For Po fractions, there was no significant change in P concentrations. The conversion of land use from paddy fields to high intensity vegetable fields was causing significant changes in soil P fractious. Management practices were causing a buildup of soil P, primarily in the Fe-Pi fraction, followed by Ca-Pi and Al-Pi fractions. If current trends continue, a 30%-70% increase in TP could be expected in the next 20 years. Farmers in the area should reduce P application and use to maximize P uptake.
基金the Natural Science Foundation of China (No. 40571093)the National Field Station Fund
文摘We investigated the patterns of phosphorus transport from purple-soil cropland of 5° and 10° slopes with bare and vegetated surfaces,respectively.Each type of land was tested under a simulated moderate rainfall of 0.33 mm/min,a downfall of 0.90 mm/min,and a rainstorm of 1.86 mm/min.Runoff dynamics and changes in the export amount of phosphorus are influenced by the rainfall intensity,the slope and surface conditions of cropland.The vegetation diverts rain water from the surface into soil and helps the formation of a subsurface runoff,but has little influence on runoff process at the same sloping degree.Vegetated soil has a smaller phosphorous loss,particularly much less in the particulate form.A heavier rainfall flushes away more phosphorous.Rainwater percolating soil carries more dissolved phosphorous than particulate phosphorous.Understanding the patterns of phosphorous transport under various conditions from purple soil in the middle of Sichuan basin is helpful for developing countermeasures against non-point-source pollution resulting in the eutrophication of water bodies in this region that could,if not controlled properly,deteriorate the water quality of the Three Gorges Reservoir.
文摘Soils from urban and suburban areas are normally enriched with phosphorus (P). Sixteen urban soils with a wide range of total P concentrations under typical urban land uses were sampled and analyzed for extractable P concentrations using water, sodium bicarbonate and citric acid. Meanwhile the soils were artificially leached in columns and P concentrations in the leachates were determined. With linear regression a two-stage linear relationship was found to exist between concentrations of P in the leachates …
文摘Phytochemical constituents of the shoots and roots extract of chosen eight medicinal plants （Plantago major, Verbesina encelioides, Glinus lotoides, Helotropium supinum, Mentha microphylla, Euphorbia hirta, Juncus subulatus and Convolvulus arvensis） were estimated using standard qualitative analysis. The extract contained alkaloids, glycosides, saponins, phenols, tannins, f[avonoids and terpenoids in some medicinal plants while others contain some only of these phytochemical components. Allelopathic effect of the various concentrations of the extracts on the soil algal diversity was also investigated. Wollea saccata was the only algal species disappeared from all applied investigated plant extracts. Phormidium richardsii, Monoraphidium braunii, Eunotia verneris and Nitzschia bilobata were the highly sensitive algal species to all applied shoot and root extract from all tested plants, they disappeared from most of the studied plants. On the other hand, Phormidium animale and Chlorella neustonice were highly tolerant algal species to all applied extracts. Counts of Cyanophyceae, Chlorophyceae and Bacillariophyceae were decreased by addition of some investigated medicinal plants extracts such as Juncus subulatus, Convolvulus arvensis and Euphorbia hirta. So the authors can use these plants extracts in biocontrol of the nuisance of algal bloom or any other microorganisms. Also, these plants may be useful to recover eutrophic water which needs further investigation.
