Denitrifying bioreactors are an edge of field practice used to remove nitrates from tile drainage water before they are discharged to a stream, ditch or other surface water source. The bioreactor itself is just a trench filled with wood chips and equipped with control structures to regulate inflow and outflow. Tile water drains directly into the wood chips where bacteria convert nitrates from the water into nitrogen gas, eliminating them as a source of pollution.

Comparisons of inflow and outflow samples from working bioreactors in the Middle Cedar show a 42% reduction in nitrate concentration.

Photos for the gallery below were taken by Joe Murphy, Senior Communications Manager for the Iowa Soybean Association.