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Nutrient reduction: Scale of change needed and potential benefits

Matt Helmers for Progressive Dairyman Published on 22 February 2019

Nutrient losses from agricultural systems in the Mississippi River basin have contributed to the hypoxic zone in the Gulf of Mexico. In 2008, in response to this challenge, the EPA’s Hypoxia Task Force released an action plan for a national strategy to reduce, mitigate and control hypoxia in the northern Gulf of Mexico and improve water quality in the Mississippi River basin (Hypoxia Task Force).

The action plan indicated significant (i.e., 45 percent) reductions in riverine nitrogen and phosphorus loads are needed to achieve the goal of reducing the size of the hypoxic zone and improving water quality in the basin.

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One of the main items in the 2008 action plan was the call for state-level nutrient reduction strategies. As a result, the 12 states bordering the Mississippi and Ohio rivers have developed and begun implementing comprehensive nutrient reduction strategies.

These efforts have led to increased discussions on what practices can be most effective for nutrient reduction and what might be the benefits of these practices. The practices range from in-field nutrient management to cover crops to land-use change to edge-of-field practices.

Moving forward, there needs to be increased discussion on how we can achieve the level of implementation necessary to reach the desired outcomes. For example, one scenario to reach the nitrate-N reduction targets of the Iowa Nutrient Reduction Strategy includes using the maximum return to nitrogen (MRTN) application rate to all corn acres, 60 percent of corn-soybean and continuous corn acres having cover crops (about 12.5 million acres), 27 percent of all agricultural land being treated with a wetland and 60 percent of the tile-drained acres being treated with a bioreactor.

For wetlands, it was assumed each wetland (10 acres of wetland surface area with 35 acres of buffer) treats 1,000 acres of agricultural land, which would result in approximately 7,600 wetlands for this scenario. For bioreactors, it was assumed each bioreactor treats 50 acres of subsurface-drained land, which would total approximately 120,000 bioreactors in Iowa alone.

This scenario was estimated to have the potential to reduce nitrate-N loads by 125,000 tons per year, which is an overall nitrate-N load reduction in Iowa of approximately 42 percent at an annual cost of approximately $755,518,000.

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While the scale of implementation and costs associated with reaching the nutrient reduction strategy goals seem daunting, it is important to recognize the additional benefits that could come from pursuing nutrient reduction. Some of these practices may improve soil health, such that we have a more resilient agricultural landscape. In addition, there are likely to be economic benefits of cleaner water.

It is also important to consider what practices may work best in certain areas and make sure we are targeting the right practice for the nutrient and nutrient transport pathway of concern. For example, wetlands and bioreactors are going to work in areas where we have subsurface drainage systems where those systems can be intercepted to allow for denitrification in the wetlands and bioreactors.

Also, while no-till can be very effective for reducing surface runoff nutrient loss, it will be less effective or not effective at all in decreasing nutrient loss via leaching. A useful tool increasingly used in watershed planning is the Agricultural Conservation Planning Framework (ACPF, watersheds). This tool is being used to leverage high-resolution geospatial data to help local communities address their conservation needs. Through use of tools like this, we can make sure we are trying to be as efficient as possible in utilizing conservation dollars.

An often-overlooked aspect to large-scale implementation of nutrient reduction practices is the number of well-trained individuals who will be needed. We need agricultural and conservation specialists who can work with farmers and landowners to implement these practices in targeted and high-impact areas. We need them in both the private and public sectors. Developing and delivering programs and classes that can train individuals to promote and assist in nutrient reduction practice implementation is crucial if we are going to make significant progress on reaching our nutrient reduction goal. This need will extend throughout the Midwest to other areas where nutrient reduction is critical.

With this, there is a potential for a significant increase in job opportunities for individuals trained and willing do this work. In addition, there are likely to be small business opportunities throughout rural landscapes to site, design and maintain these various practices and provide technical assistance to farmers and landowners. This has a potential to be a win-win for our local, rural communities.

While these nutrient reduction strategies are a big investment, there is the potential they could stimulate our local economies and make for more resilient agricultural systems. I would encourage you all to learn more about what your state is doing to reduce nutrient loss to downstream water bodies and what practices might work best in your area.  end mark

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Matt Helmers
  • Matt Helmers

  • Professor, Ag & Biosystems Engineering
  • Iowa State University
  • Email Matt Helmers

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