The problem being solved: In agricultural areas, poor drainage can cause soil to become waterlogged, leading to poor growth of crops. Drainage pipes (also known as field tiles) are effective for keeping soil from becoming waterlogged, but nitrogen in the water removed from the soil in this way often ends up accumulating at harmful levels in nearby streams, rivers and lakes—eventually creating “dead zones” where fish and other species cannot survive. This phenomenon is estimated to cost the U.S. seafood and tourism industries $82 million per year in losses. 

The technology solution: An experimental saturated buffer, jointly developed by researchers from the U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS) and Iowa State University, intercepts a field tile where it crosses a buffer area—land adjacent to a ditch, stream or river populated by trees or other perennial plants. Some of the drainage water is diverted into a perforated pipe that slowly distributes it through the soil in the buffer area. This creates favorable conditions for nitrogen in the water to be removed by the perennial plants and microbes within the soil. Saturated buffers require little maintenance and do not decrease the amount of land available for farming or the productivity of those croplands.  

The tech transfer mechanisms: To promote awareness of the saturated buffer technology within the agricultural community, researchers from ARS and ISU collaborated on 12 peer-reviewed journal articles, 75 professional or outreach presentations, training materials and videos, and more than 100 field tours. Project partners have visited numerous locations with to assess a site’s potential for saturated buffer use and to discuss the technology with local, state and federal practitioners, engineers and landowners. These efforts have been crucial to the initial and ongoing adoption of the practice. 

The impact: At a network of demonstration sites, saturated buffers removed an average of 42% of the harmful nitrates from tile drainage water. Since then, the technology is quickly becoming accepted across the Midwest. A Saturated Buffer Conservation Practice Standard, developed with the USDA Natural Resources Conservation Service, was implemented in 2016 and the practice was incorporated into the Conservation Reserve Program as part of the Clean Lakes, Estuaries and Rivers Initiative. The USDA also developed a tool to identify the sites where saturated buffers will have the greatest impact on water quality, then partnered with multiple state and local organizations on a project. In all, 48 saturated buffers were installed in two Iowa counties in 2021. The developers estimate the technology’s use could grow to 100 locations per year in Iowa, and surrounding states are implementing similar programs.