Soil and Water Conservation Practices Addressing Nutrient Runoff in the Mississippi River Basin by State, According to the Agricultural Nutrient Policy Council

  

    The Mississippi River Basin drains 40% of the continental U.S. and encompasses 31 states. One of the biggest water quality concerns for the basin is nutrient runoff, specifically nitrogen and phosphorus runoff. This is the source of the dead zone in the Gulf. The Agricultural Nutrient Policy Council’s article ‘One Basin With Many Solutions’ characterizes the most common solutions the nutrient runoff by state, including eight key basin states: Illinois, Iowa, Ohio, Missouri, Kentucky, Arkansas, Minnesota, and Mississippi. A great lesson in Mississippi River geography is provided by the legendary Johnny Cash, in his 1962 song ‘Big River,’ where he details chasing a woman down the river from St. Paul, Minnesota, through Davenport, St. Louis, Memphis, Baton Rouge, and down to New Orleans, hoping in vain to meet her again to profess his love.   

     In Illinois, farmers are collaborating with organizations in adopting cover crops and strip-till systems to improve soil structure and water quality. Cereal rye is one cover crop that prevents erosion and uses up some of the excess nutrients. According to Grower Experts:

“Strip tillage is a conservation tillage practice that involves tilling narrow strips of soil where crops will be planted, leaving the areas between the rows untilled. This method combines the benefits of no-till and conventional tillage, promoting soil health while providing a suitable seedbed for crop establishment.”

     Strip tillage allows fertilizer to be placed more precisely, reducing runoff.

     In Iowa, the use of saturated buffers and bioreactors to capture and treat nutrient excess is common and growing. In a model called 'batch and build,' the state is increasing nutrient runoff prevention and treatment. According to the Iowa Agriculture Water Alliance:

“The Batch and Build model was created by Polk County Public Works in an effort to drastically scale up the number of saturated buffers and bioreactors in the county. For years, only one or two were installed a year in the county. By streamlining the process, removing burdens for landowners and farmers, and providing additional funding, Polk County has scaling that up to more than 100 per year. Statewide, these edge-of-field practices have now increased 650% year over year!”

     Iowa is a huge farm state with its famously productive loess soil. Thus, strong efforts to reduce nutrient runoff in the state can have an impact on reducing the hypoxia occurring in the Gulf.

     I wrote about saturated buffers, bioreactors, and other methods of nutrient runoff management previously.

     According to the Agricultural Nutrient Policy Council (ANPC), Ohio emphasizes the use of two-stage ditches and restored wetlands for nutrient management. Two-stage ditches are best used in flat fields with subsurface drainage installed. It is used to reduce moisture where subsurface drainage outlets are submerged in water. It reduces nutrient runoff, improves bank stability, and improves plant-soil-water interactions, which aids nutrient recycling. These require very little maintenance and are long-lasting.

     Subsurface tile drainage can also drain wetlands. Wetland restoration is only suitable for actual wetland sites with hydric soils. Studies have shown that restored wetlands can capture and retain about two-thirds of the nitrogen and phosphorus that enter. They are often combined with upland vegetative buffers that filter pollutants and reduce sediment runoff. 

Restored Wetland

     Ohio has conservation initiatives, programs such as H2Ohio, and even a nutrient stewardship certification.

     The State of Missouri ran an edge-of-field water quality monitoring project from 2017 to 2022 to compare nutrient runoff rates after certain practices and combinations of practices were implemented. This data-driven approach gives insight into what works and how well each practice works, and can inform what the best combinations of practices will work best for each area. 

     Two combo methods were studied: grassed waterways with conventional terracing and grassed waterways with cover crops. These were measured against conventional farm fields to compare cover crops vs. non-cover crops on surface tile-drained fields. Some results are shown below.

     Kentucky has emphasized good water quality planning and provides an online water quality planning tool for farmers. They also provide very good information on the best management practices (BMPs) for agriculture. Streambank restoration, cover cropping, and restricting livestock access to streams are popular practices.

     Arkansas is the number one rice-producing state. Closer to the Gulf, there is more use of tailwater recovery systems. This refers to capturing runoff and using it for irrigation. Rainwater and field drainage water are collected via constructed wetlands. The wetlands filter out pathogens, nutrients, and sediment. An LSU study in 2015 studied the effectiveness of a tailwater recovery system with two wetlands, one shallow and one deep.

“The results during a critical crop season showed that the constructed wetland system was effective in reducing suspended solids and nutrient levels in runoff. The mean concentrations of Total kjeldahl nitrogen (TKN), total phosphorus (TP), soluble reactive phosphorus (SRP), and total suspended solids (TSS) were reduced by 65%, 59%, 45%, and 90% respectively, as runoff moved from the shallow to the deep wetland system.”

     According to the USDA’s Natural Resources Conservation Service (NRCS)

“A tailwater recovery system is suitable for use on lands that have a properly designed and installed irrigation or subsurface drainage system where recoverable irrigation runoff, subsurface drainage outflows, or rainfall runoff are expected under current or planned management practices.”

     The ANPC notes:

“Additionally, rice farmers are using precision levees and alternate wetting and drying techniques, conserving water and decreasing nutrient leaching. Their efforts are contributing to better water quality outcomes while maintaining high yields.”

     In Minnesota, the use of saturated buffers and bioreactors at the edge of fields in concert with drainage tiles in corn and soybean fields is commonplace. Saturated buffers divert water into a buffer area where it can be naturally treated by microbes to reduce the amount of nutrients entering streams.

     Bioreactors are effective at removing nitrates from field runoff water. These are more complex but utilize common materials like wood chips.

     Another common practice in Minnesota is constructing native vegetation buffers between farm fields and streams. They also help improve wildlife habitat and reduce flooding.

     In Mississippi, cross-fencing and rotational grazing are commonly used. These keep livestock away from areas for time periods long enough to allow preferred native grasses to grow, which helps to control soil erosion and improve filtering. Alternating cattle and reducing feeding time in specific areas prevents overgrazing. This can be combined with removing some invasive grasses and planting desirable grasses.

     Finally, the ANPC notes:

“From the prairies of Minnesota to the rice fields of Arkansas, farmers and ranchers across the Mississippi River Basin are demonstrating that clean water and productive agriculture are not mutually exclusive. Through innovative, science-backed practices such as cover cropping, rotational grazing, precision nutrient application and innovative drainage solutions, they're leading the way in reducing nutrient runoff and restoring the health of our waterways.”

“These efforts aren’t isolated success stories — they're part of a coordinated movement on farms across the country. With continued support from conservation programs, local partnerships and the agricultural retail community, the impact will only continue to grow. Clean water is everyone’s responsibility, and thanks to these producers, progress is not only possible —it’s already happening.”

 

 

References:

 

One Basin With Many Solutions: Farmers, ranchers, and ag retailers lead the charge for clean water. Agricultural Nutrient Policy Council. One Basin With Many Solutions — Agricultural Nutrient Policy Council

Improving Water Quality From the Ground Up: A primer on agricultural conservation practices — and why they make a difference. Agricultural Nutrient Policy Council. Improving Water Quality From the Ground Up — Agricultural Nutrient Policy Council

What is Strip Tillage: Benefits and Examples. Grower Experts. What is Strip Tillage: Benefits and Examples – GrowerExperts

Batch and Build. Iowa Agriculture Water Alliance.  Batch and Build - Iowa Agriculture Water Alliance

Open Channel/Two-Stage Ditch (NRCS 582). AgBMP. Ohio State University Extension. Open Channel/Two-Stage Ditch (NRCS 582) | AgBMPs

Restored Wetlands (NRCS 657), AgBMP. Ohio State University Extension. Restored Wetlands (NRCS 657) | AgBMPs

Missouri Edge of Field.  2017-2022. FIVE-YEAR WATER QUALITY RESEARCH PROGRAM. Missouri Corn, Missouri Soybeans, Missouri Fertilizer Control Board, Missouri Dept, of Natural Resources. August 10, 2023. MoCorn_EoF_FINAL-UPDATED-08.10.23_Pages.pdf

Develop Your Agriculture Water Quality Plan. Kentucky.gov. Develop Your Agriculture Water Quality Plan - Kentucky Energy and Environment Cabinet

Tailwater recovery system as a best management practice to improve irrigation water quantity and quality in Louisiana. Changyoon Jeong, Ernest Girouard, and Patrick Colyer. Louisiana Water Resources Research Institute. Louisiana State University. 2015. Tailwater recovery system as a best management practice to improve irrigation water quantity and quality in Louisiana | LSU Louisiana Water Resources Research Institute

IRRIGATION AND DRAINAGE TAILWATER RECOVERY. CODE 447. USDA NRCS. September 2022. Conservation Practice Standard Irrigation and Drainage Tailwater Recovery (Code 447)

Improved design, performance, and implementation of saturated buffers. Minnesota Dept. of Agriculture. Improved design, performance, and implementation of saturated buffers | Minnesota Department of Agriculture

Bioreactor Research. University of Minnesota. Bioreactor Research | Southwest Research and Outreach Center

Conservation Benefits Mississippi Ranch & Improves Water Downstream. USDA. November 7, 2013. Conservation Benefits Mississippi Ranch & Improves Water Downstream | Home