Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2006
Publication Date: 4/20/2007
Citation: Brock, E.H., Ketterings, Q.M., Kleinman, P.J. 2007. Phosphorus leaching through intact soil cores as influenced by type and duration of manure application. Nutrient Cycling in Agroecosystems. 77(3):269-281. Interpretive Summary: The loss of phosphorus in runoff from agricultural soils continues to be a major water quality concern due to the biological enrichment of surface waters. Historically, subsurface transport has not been viewed as a major loss pathway for phosphorus. This study examines subsurface phosphorus loss from soils with a range of manure management histories. Mechanisms controlling phosphorus release to leaching water changed with manure application history. Findings of this study can be used to pinpoint sources of phosphorus in subsurface flow.
Technical Abstract: Leaching of phosphorus (P) in manure-amended soils has received increased attention as a significant source of non-point source P pollution. Intact soil cores were collected from fields on a farm in Southern New York to test the effects of long-term dairy or poultry manure application on P leaching. Nine fields were selected (four poultry, four dairy, and one unamended) to represent a broad range of P saturation levels (5.3 to 62.4%) in the topsoil (0-7.5 cm). Water was applied weekly at a rate matching a 1-yr return period storm for the study area (230 mm hr-1). Dissolved reactive P (DRP) losses in leachate from all soil cores ranged from 0.007 to 0.055 kg P per ha, except in two fields with long-term histories of dairy and poultry manure application, where losses averaged 0.21 and 0.45 kg P per ha, respectively. Hydrographs of the field with the dairy manure history suggested preferential flow as an explanation of leachate P enrichment. In the poultry manure amended field, high levels of soil P saturation throughout the profile suggested subsoil P desorption as a factor controlling leachate P. Surface application of dairy manure to the soil cores (167 kg total P per ha) increased the mean leachate DRP concentration from 1.5 to 10.5 fold. After five leaching events spanning 22 days, DRP concentrations remained 2.0 to 13.4 fold above pre-manure application levels. This study points to saturation of P in subsoils by long-term manure application as a key concern to P loss in leachate and highlights the role of annual manure additions on subsurface P loss potential.