Phosphorus release from intact soil monoliths of manure amended fields under simulated snowmelt flooding

Anaerobic conditions developed in soils with flooding can enhance the release of soil phosphorus (P) to overlying water, but little information is available for soils with a long history of manure application. We examined the P release from manure-amended soils under simulated snowmelt flooding. Intact monoliths from manured (solid-swine, SSM or liquid swine, LSM) and unamended (control) field plots were collected from Carman, Manitoba. Monoliths were frozen for seven days, then thawed, flooded and incubated at +4±1 °C. Redox potential, pH, and concentrations of dissolved reactive P (DRP), Ca, Mg, Fe and Mn in pore water and floodwater were determined weekly up to 56 days after flooding (DAF), and then at 84 DAF. Redox potential decreased with DAF with a greater, and more rapid, decrease in SSM (from initial value of ~300 mV to < 0 mV by 84 DAF) compared to LSM and control (~100 mV by 84 DAF). Pore water and floodwater DRP concentrations were significantly greater in manured treatmen...