DENITRIFICATION IN A GRASSED AND A WOODED, VALLEY AND RIDGE, RIPARIANECOTONE

Denitrification is one of the major mechanisms responsible for changes in NO3--N concentrations in shadow groundwater as subsurface flow pas ses from agricultural fields to the stream In this study, denitrificat ion is examined in a grassed and wooded riparian ecotone common to the Valley and Ridge physiographic province in Pennsylvania. Denitrificat ion rates of 102 and 10 mu g N kg(-1) soil d(-1) were measured using s oil slurry and intact core incubation techniques, respectively. The gr assed riparian site exhibited greater denitrification rates than the w ooded site. Carbon amendments resulted in an increase in denitrificati on at the wooded site and suggest that denitrification may be C limite d at this site. Denitrification generally decreased with distance away from the stream and also decreased with depth in the soil. Patterns o f denitrification measured with tbe soil slurries corresponded closely to patterns of soil NO3- content.