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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #121016
Title: PHOSPHORUS IN OVERLAND FLOW IN RESPONSE TO MANURE APPLICATION AND LANDSCAPEPOSITION

Author
item MCDOWELL, RICHARD - PENN STATE UNIVERSITY
item Sharpley, Andrew

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2001
Publication Date: 1/20/2002
Citation: Mcdowell, R.W., Sharpley, A.N. 2002. Phosphorus in overland flow in response to manure application and landscapeposition. Journal of Environmental Quality. 31:217-227.

Interpretive Summary: Phosphorus is a key element in the nutrition of plants and the eutrophication of surface waters. The loss of phosphorus from soil to surface waters is mediated by hydrological conditions and can occur in both dissolved and particulate forms. In the continental climate of the northeast U.S., most phosphorus is lost via overland pathways. Once in transport, dissolved and particulate phosphorus can undergo changes via sorption and desorption processes. Consequently, where a soil lies within a landscape can have a profound effect on the concentration of phosphorus lost, a process not well understood. We hypothesize that if a recently manured soil is far enough upslope, it is possible that the concentration of phosphorus in overland flow may decrease to less than that required to cause eutrophication by the time it reaches a surface water body. We applied swine manure at different positions on a slope and measured the loss of phosphorus in surface runoff and found that the concentration of phosphorus on overland flow decreased with increasing flowpath length. The loss of total phosphorus from a high phosphorus soil was more than from a low phosphorus soil, even with manure applied. Thus, while phosphorus loss in overland flow is affected by where manure is applied relative to flowpath length, soil phosphorus concentration should not be discounted when looking at areas of potential phosphorus loss within a watershed.

Technical Abstract: The loss of P in overland flow varies as a function of the spatial distribution of soil P, management and hydrological pathways. This paper examines the effect of time and landscape position on P loss from two soils (Watson and Berks) packed in boxes of varying length (0.5, 1.0, 1.5, 2.75 and 4.0 m long, 15 cm wide, 10 cm deep). The effect of flow-time and landscape position on P loss were examined by collecting overland flow samples at 5 min intervals for 30 min (5 cm/hr rainfall) without and with 75 kg P/ha applied as swine manure over 0.5 m of the slope at distances of 0 to 3.5 m from the downslope collection point. Dissolved reactive P concentration was more closely related to the proportion of clay in sediment of overland flow before (r = 0.98) than after (r = 0.56) manure application. This was attributed to increased aggregate stability and the transport of the coarser particles after applying manure. The concentration of dissolved and particulate P fractions decreased with increasing flowpath length, due to dilution rather than sorption of P by surface soil during overland flow. The loss of total P (mainly as particulate P) from the Watson soil was more than from the Berks, even with manure applied. Thus, while P loss in overland flow is affected by where manure is applied relative to flowpath length, soil P concentration should not be discounted when looking at areas of potential P loss within a watershed.