GUIDELINES / 1.0 Water Quality
1.12 Buffers for Nitrogen
Most nitrogen (N) is lost to surface water through overland flow and to groundwater by leaching of nitrate (NO3). Plant uptake of N generally does not result in permanent removal as N is eventually returned to the soil upon death and decay of plants unless harvested (see 1.26).
Denitrification is the primary process for permanently removing N with a buffer. In denitrification, anaerobic bacteria transform nitrate to nitrogen gas (N2) which is released into the atmosphere. Below are some key site characteristics that promote effective denitrification with buffers.
Key Design Considerations
- Soils should be rich in organic matter, often provided by decaying plant material.
- Soils need to be wet or hydric.
- Soils should have moderate to high permeability to encourage infiltration and yet should be poorly drained to have anaerobic conditions. Deep coarse sands or gravel may allow dispersion to deeper groundwaters before denitrification occurs.
- Low temperatures and acidic soils will inhibit denitrification.
- See 1.19 for buffer width recommendations for surface N runoff.
- See 1.15 for shallow groundwater flow.