Watershed Scale, Not Field Scale

If we hope to significantly improve water quality in Iowa and still farm profitably, we are going to need to change our mindset about our agricultural systems. We are going to need to start thinking in terms of watersheds.

Each spring I teach a graduate course for the Iowa State University Master of Science in Agronomy distance program called “Agronomic Systems Analysis.” The course is comprised of field-scale case studies that require students to consider how complex decisions must be made by taking into consideration agronomic, economic, environmental, and social implications of the decisions. This year, I incorporated a new lesson that goes beyond field scale but encourages the students to address the issues at the watershed scale.

shelbyemphemeral-e1506974374896The point of this lesson is to have students think not about a single farm or field but to think about where to target practices to be the most effective. And which practices will draw the most reduction of nutrients being lost. This is not rocket science. It has been well established that sloping land is prone to erosion. These are the areas where no-tillage and cover crops are going to be the most effective at keeping soil and phosphorus in place. It’s well understood that well drained soils with very little slope are prone to nitrate leaching. These are the areas where bioreactors, wetlands and cover crops will be most effective in reducing nitrate movement into flowing water.

For several years, the Iowa Learning Farms and Iowa State University Extension and Outreach have been talking about implementing conservation practices and the scale of conservation practice adoption that must occur to reach nutrient reduction goals. For instance, one scenario calls for statewide adoption of MRTN (maximum return to nitrogen) rates along with 12 million acres of cover crops, 12 million acres of no-tillage, 6 million acres treated by bioreactors, and 7.5 million acres treated by wetlands. That effort to date has achieved approximately 625,000 acres of cover crops, 5 million acres of no-tillage, 950 acres treated by bioreactors and 42,200 acres treated by wetlands. We have a long way to go.

Cover crops

Reaching conservation practice goals will take everyone thinking about how his or her footprint impacts the watershed as a whole. It will take targeting practices for maximum effectiveness with minimal impact to the cost of production. Wetlands can be installed to treat water flowing from multiple fields. Prairie strips in strategic locations can minimize sediment and phosphorus loss. Saturated and riparian buffers will reduce nutrient movement and streambank sloughing of rivers and streams. It can even be as simple as installing a waterway to connect waterways from adjacent fields or no-tilling soybean into corn residue.

There can be watershed and community benefits that extend beyond the fence. Many practices can support efforts to provide habitat for pollinators, monarchs, song birds, game birds, waterfowl and deer.

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We cannot meet the Iowa Nutrient Reduction Strategy goals and improve habitat without changing our mindset about how we farm and the use of conservation. Conservation practices are most effective if they are targeted specifically in areas that will result in a continuous, complimentary system across the watershed.

How can we help you think on a watershed scale?

Mark Licht

Mark Licht is an Iowa Learning Farms team member and Assistant Professor and Extension Cropping Systems Specialist at Iowa State University.