摘要
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.
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 1 were found for soluble and loosely bound Pi (SL-Pi),aluminum-bound Pi (Al-Pi),calcium-bound P i (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 fractions.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
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)
