Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: November 3, 2004
Publication Date: November 3, 2004
Citation: Green, V.S., Dao, T.H., Cavigelli, M.A., Flanagan, D.C. 2004. Phosphorus fractions in aggregates of organic and conventional cropping systems [abstract]. American Society of Agronomy Annual Meeting Abstracts [CDROM]. No. 4279. Technical Abstract: During a soil erosion event, water-soluble P can move with runoff while complexed P can move with suspended sediments and colloids. To compare the effect of cropping systems on potential P losses by erosion, we measured P distributions among five aggregate size classes. Soil samples (0-5 cm) from organic (ORG), conventional till (CT), and no-till (NT) cropping systems and a woodland site were separated into five aggregate size classes from less than 0.05 to greater than 2 mm by wet sieving. Water extractable P (WEP), net EDTA-extractable P (nEDTA-P), and net EDTA- phytase hydrolysable P (nEDTA-PHP), representing labile and complexed inorganic and organic bioactive P forms were determined for each size class. The concentration of P fractions in all size classes was greater in NT soils than in CT, ORG, and woodland soils. Within a cropping system, WEP, and nEDTA-PHP concentrations were generally greater in aggregates larger than 0.2mm. For any given size class, nEDTA-P and nEDTA-PHP concentrations were similar (70 to 110 mg P/kg soil), indicating that management practices should focus on both inorganic- and organic-P release from soils as both are potential contributors to water quality degradation from eroded sediments. Accumulation of P in easily erodible aggregate size classes increases the risk of mobilization of inorganic and organic P from surface soils.