Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2004
Publication Date: 3/20/2005
Citation: Kleinman, P.J.A., Srinivasan, M.S., Sharpley, A.N., Gburek, W.J. 2005. Phosphorus leaching through intact soil columns before and after poultry manure application. Soil Science. 170(3):153-166. Interpretive Summary: Recent application of manure can increase phosphorus (P) loss from soil in subsurface flow, which can contribute to eutrophication of surface waters. This study looked at factors affecting P transport in subsurface flow from intact soil columns. Concentrations of P in column leach water (leachate) were negligible before manure application but increased dramatically after poultry manure was broadcast. Even though concentrations of P in leachate declined over time, they remained significantly elevated for 100 days after the manure was applied. Examination of subsurface flow using a dye tracer revealed that large, continuous channels, such as root channels and earthworm burrows, likely served as preferential flow pathways for manure P. Results of this study provide insight into the chemical and physical nature of sub-surface P transport.
Technical Abstract: Recent application of manure can increase phosphorus (P) loss from soil in subsurface flow. This study investigated P leaching through two soils that are sometimes artificially drained, making sub-surface P transport a concern. Eight 30- and 50-cm deep, intact soil columns were collected. Columns were irrigated (2.4 cm day-1) before and after surface application of poultry manure (85 kg total P ha-1), continuing for 11 weeks after the application. A dye tracer (FD&C blue #1) was used to identify the presence of active macropores at the bottom of each column, and to compare properties of soil matrix with soil bordering dyed macropores. Before manure application, concentrations of total P (TP) in leachate did not exceed 0.57 mg L-1, and dissolved reactive P (DRP) was a minor fraction of TP (4-21%). Manure application resulted in significant increases in leachate P concentrations, with DRP averaging 72% of TP. However, trends in the temporal nature and magnitude of leachate P varied greatly between columns. In most columns, P concentrations in leachate peaked soon after manure application, with maximum DRP concentrations ranging from 1.1 to 11.2 mg kg-1. In some columns, concentrations increased slowly over time, with maximum DRP concentrations only 0.19 to 0.55 mg L-1. P sorption saturation of soil bordering soil macropores, evidenced by elevated Mehlich-3 P and depleted Mehlich-3 Al, point to the importance of macropores as preferential flow pathways for P. Results of this study highlight the significant, but temporally and spatially variable, nature of sub-surface P transport in manured soils.