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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #63709
Title: DENITRIFICATION RATES AT FOUR RIPARIAN ECOSYSTEMS IN THE VALLEY AND RIDGE PHYSIOGRAPHIC PROVINCE, PENNSYLVANIA

Author
item Schnabel, Ronald
item CORNISH, LEONARD - PENN STATE UNIVERSITY
item Stout, William

Submitted to: Clean Water Clean Environment 21st Century Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/8/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Nitrogen is lost from farm fields and carried into streams under common farm practices. Conservationists are looking for ways to use the nitrogen lost from fields before it reaches streams. Denitrification in streamside zones can reduce the amount of nitrogen transported from farm fields to streams. In this study, we examine denitrification in four streamside ecosystems common to much of eastern Pennsylvania. We compared the sites with a simple test we demonstrated was reliable in a previous study. The sites were wooded or grassed, underlain by different rock types, and downslope of farm fields. The three grassed sites showed higher denitrification potential than did the single wooded site. Denitrification potential was greatest near the stream and decreased with distance upslope. The path of groundwater flow to the stream controls denitrification, which is likely to be greatest near the field--streamside boundary where the groundwater is shallow, and near the stream where the groundwater is deeper. This difference in denitrification patterns will affect how much nitrogen streamside buffers can keep from entering nearby streams.

Technical Abstract: Denitrification in riparian ecosystems can reduce the amount of nitrogen transported from farm fields to streams. In this study, we examine denitrification in four riparian ecosystems common to the Valley and Ridge physiographic province in Pennsylvania. The sites are underlain by different rock types and vegetation. All sites are downgradient of farm fields. Mean site denitrification rates ranging from 0.6 to 1.9 mg N kg soil-1 day-1 were measured using intact core incubation techniques. The three grassed riparian sites each exhibited greater denitrification rates than the wooded site. Denitrification rate was correlated with moisture content but not with nitrate-N or organic carbon contents. Denitrification rates were greatest near the soil surface and at positions nearest the stream. Rates decreased uniformly with distance away from the stream and also with depth in the soil for each site. While patterns of nitrate-N, moisture and organic carbon content differ among the sites, their effects on denitrification interact to make the observed, consistent denitrification rate pattern plausible.