Riparian Buffer Effectiveness as Influenced by Vegetation Type, Buffer Width, and Groundwater Depth in the Middle Coastal Plain.

Non-point source pollution from agriculture has caused severe degradation of surface waters in the Coastal Plain of North Carolina. Riparian buffers are an important best management practice for reducing nitrate-N through vegetative uptake and/or denitrification. This study was conducted on a research farm located in the Neuse River Basin to understand the effectiveness of riparian buffers at removing nitrate-N from groundwater. Buffers at this site have been monitored for approximately ten years. The experimental design, coupled with the time span of this study, has allowed a unique longitudinal assessment of riparian buffer effect on groundwater nitrate-N in the Middle Coastal Plain. Buffers are adjacent to deeply incised drainage ditches; design consists of five vegetation types (trees, fescue grass, switchgrass, native vegetation, control), two buffer widths (7.6 m, 15.2 m), and two well depths (1.5 m, 2.1 m). Groundwater samples are taken monthly, and analyzed for NO₃-N, PO₄, CL and DOC. Previous data shows nitrate-N reductions of 12-75%, dependent upon well depth, buffer width, and vegetation type. Current data has produced similar percentages for nitrate-N reductions; however, continued monitoring is important in order to assess effects of maturation of vegetation, in addition to the continuation of data collection for the already established temporal trend line.