Area producers gathered at Lanehaven Farms near Waterloo on September 18 to get their first look at a couple of relatively new conservation practices in the state of Iowa- denitrification bioreactors and saturated buffers. In an event hosted by the Black Hawk County Conservation Soil and Water District, the Iowa Soybean Association and Hollis Farms, farmers learned two ways they can significantly reduce nutrients running off their farm fields into neighboring creeks, streams and rivers. Such a reduction is needed to improve the overall water quality in the state and help reduce the chemicals that ultimately wind up in the Gulf of Mexico, where they feed massive algae blooms that result in large areas where no aquatic life can survive.
Standing on an active bioreator utilized by Lanehaven Farms, presentations by Keegan Kult of the Iowa Soybean Association and Chad Ingels of Iowa State Extension and Outreach introduced the conservation practice, utilizing a working model to illustrate
What are denitrification bioreactors? Basically, they are pits placed in close proximity to a field’s tile system, filled with organic material, usually wood chips, which serve as a carbon food source and home for bacteria that break down nitrates. Once the pit is covered, the only tell-tale sign of the presence of a bioreactor are two control structures that extend up from the ground, one that directs the flow of water into the bioreactor, the other that regulates the flow out of the system. As water makes its way through the wood chips in the bioreactor, bacteria break down the nitrates, much like the human digestive system breaks down food after it is eaten. The chemical change that takes place as the water moves through the bioreactor results reduces the nitrates contained within the water draining from the farm field.
In addition to ecological benefits, there are several other positives associated with bioreactors:

  • They can be easily incorporated into existing conservation practices.
  • Bioreactors take up very little space, less than 0.1% of a drainage area.
  • As an edge-of-field practice, very little production area is consumed by bioreactors.
  • Bioreactors can function adequately for 12-15 years, depending on environmental conditions.

One of the challenges incorporating dentrification bioreactors into producers’ operations is cost. Depending on the size of the bioreactor, it can cost $8,000-$10,000 to install. And while the benefits to the environment and overall water quality are significant, there really are no direct financial benefits to the producer.
Another fairly new conservation practice in Iowa was introduced by Nathan Utt of Ecosystem Services Exchange, a company that has been researching the benefits of saturated buffers. Similar to bioreactors, a saturated buffer has control structures to regulate in the flow of water as it drains from the farm field. Instead of wood chips, the system uses a shallow lateral line to intercept tile lines before they release water into a stream. The lateral line has control structures that raise the water table and slow outflow, allowing the buffers to naturally remove nutrients such as nitrate and phosphorus. Initial results from areas studying the effects of saturated buffers indicate the practice has the potential to reduce virtually all of the nitrates found in the water draining from farm fields. While the early returns are very promising, Utt cautioned there is still more research that needs to be done to hone the practice.
Producers in the Miller Creek Watershed interested in learning more about bioreactors or saturated buffers may view highlights of the Field Day by logging on to They may also contact Shane Wulf at the Black Hawk Soil & Water Conservation District Office, 319-296-3262, to learn more about potential cost share opportunities to implement these conservation practices in their farming operations.