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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #310912
Title: Chemical and isotopic tracers illustrate pathways of nitrogen loss in a cranberry bed

Author
item Kennedy, Casey
item Buda, Anthony
item Kleinman, Peter
item DEMORANVILLE, CAROLYN - University Of Massachusetts

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2015
Publication Date: 7/14/2015
Citation: Kennedy, C.D., Buda, A.R., Kleinman, P.J., Demoranville, C.J. 2015. Chemical and isotopic tracers illustrate pathways of nitrogen loss in a cranberry bed. Journal of Environmental Quality. 51(4):883-897.

Interpretive Summary: Cranberry producers are currently focused on improving water quality associated with the flooding and subsequent draining of cranberry bogs. Researchers with ARS’s Pasture Systems and Watershed Management Research Unit analyzed naturally occurring chemical and isotopic “signatures” of surface water and groundwater to trace sources of nitrogen loss from a cranberry bed. The principal sources of nitrogen in drainage water were found to derive from cranberry bog soils and groundwater. Identifying these sources is vital to helping farmers to target water quality mitigation efforts.

Technical Abstract: Limited research exists on the hydrological processes driving nitrogen (N) loss from cranberry production, which has been identified as a prominent source of watershed N loading in southeastern Massachusetts (MA). To quantify the hydrological processes underlying N export in cranberry farms, the geochemical “signature” of stable isotope ratios of oxygen (d18O) and chloride in environmental waters (e.g., precipitation, irrigation water, surface water, and groundwater) was exploited to infer transport pathways and sources of N in harvest floodwater for a 1.2-ha cranberry bed in MA. In 2012, the cranberry bed was found to be a net source of total N (TN) and could be implicated in the export of 72 mol of TN to surface water. In contrast, the bed was a net sink of dissolved inorganic N during the harvest flood, presumably reflecting a pattern of relatively low amounts of organic matter accumulated in recently renovated cranberry beds. Systematic increases in TN concentration with decreasing stage height were inversely related to the component fraction of irrigation water in floodwater, suggesting that the elevated concentrations of TN in floodwater were derived from sources within the bog, especially soil water and groundwater. In porewater groundwater of the cranberry bed, spatial patterns of N and chloride were consistent with nitrate derived from precipitation, and ammonium derived from ammonium-based fertilizer and re-mineralization of organic matter. The morphology of the subsurface peat layer was shown to exert a dominant control on patterns of groundwater exchange with the cranberry bed and, possibly, on variations in ammonium concentration of porewater groundwater.