During a soil erosion event, water-soluble forms of C, N, and P can move with runoff while complexed forms of C, N, and P can move with suspended sediments and colloids. Previous studies on this soil type have shown that concentrations of C, N, and P vary among aggregates of different sizes with greater concentrations in macroaggregates than microaggregates. Soil samples (0-5 cm) from a no-till (NT) cropping system were separated into five aggregate size classes from less than 0.05 to greater than 2.0 mm by wet sieving. Aggregate samples were incubated at 25 C and 60% water holding capacity for 56 days. Headspace was sampled regularly to measure CO2 evolution; soil samples were taken from the incubation vessels periodically to measure water extractable P (WEP), EDTA-extractable P (EDTA-P), and EDTA- phytase hydrolysable P (EDTA-PHP), representing labile and complexed inorganic and organic bioactive P forms. Soil samples were also analyzed for NO3- to determine N-mineralization rates. Cumulative CO2 evolution and N-mineralization were greatest in the macroaggregates sizes. Concentration of P in the different P-fractions was greater in macroaggregates. A shift among P-fractions over time was also observed. These data represent the fate of C, N, and P in different aggregate sizes.
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