Groundwater nitrate following installation of a vegetated riparian buffer

Substantial questions remain about the time required for groundwater nitrate to be reduced below 10 mg L− 1 following establishment of vegetated riparian buffers. The objective of this study was to document changes in groundwater nitrate–nitrogen (NO3–N) concentrations that occurred within a few years of planting a riparian buffer. In 2000 and 2001 a buffer was planted adjacent to a first-order stream in the deep loess region of western Iowa with strips of walnut and cottonwood trees, alfalfa and brome grass, and switch grass. Non-parametric statistics showed significant declines in NO3–N concentrations in shallow groundwater following buffer establishment, especially mid 2003 and later. The dissolved oxygen generally was > 5 mg L− 1 beneath the buffer, and neither NO3–N nor DO changed significantly under a non-buffered control area. These short-term changes in groundwater NO3–N provide evidence that vegetated riparian buffers may yield local water-quality benefits within a few years of planting.