By George Boody
Governor Mark Dayton announced in January his proposal to require an additional 125,000 acres of perennial vegetation along lakes, rivers and streams. There is a long history of utilizing such living borders to filter out fertilizers and herbicides, while fortifying streambanks and reducing the amount of eroded soil that ends up in the water. While not a silver bullet, establishing buffer protections between our crop fields and our water is, as LSP farmer-member Darrel Mosel says, “ …one of the most significant farmland stewardship initiatives for water quality and wildlife habitat proposed by a Minnesota governor in decades.…”
The Land Stewardship Project decided to support this proposal after talking with leaders who are farmer-members. As proposed, the initiative emphasizes stewardship of land and water, is supported by sound science and is flexible enough to provide options for sizing buffers appropriately and to allow them to be used as working farmland.
Buffer Strips 101
Vegetative buffers, sometimes called filter strips, are typically from 16.5 to 120 feet wide. These strips are designed with perennial vegetation such as grass to intercept runoff that also may carry sediment, nutrients and other contaminants into sensitive areas such as streams, lakes, wetlands or drainage ditches. Fifty-foot buffers are already required on “public waters” in Minnesota’s agricultural areas by shore land management rules. Several reports have been done on compliance and found that a sizeable number of landowners have required buffers in place, but others do not. Some counties have high rates of compliance. In Dakota County, for example, 99 percent of the Department of Natural Resources-designated shore land has a 50-foot buffer.
Governor Dayton’s initiative calls for uniform enforcement of buffer requirements and would extend 50-foot strips to perennial waters not now included in the state’s current inventory of public waters. It would not change Minnesota ditch law. Perennial waters are waters having a defined bed and bank, and have flowing water during the majority of the growing season in most years. A recent Board of Water and Soil Resources assessment showed that this may apply to about 64 percent of streams in https://landstewardshipproject.org/cmsimage/1495/large67 counties that are planted to more than 30 percent cropland.
The Science Behind Buffer Strips
Extensive monitoring of established buffers, experiments with buffer configurations and modeling have all shown that these living filters can significantly reduce sediment, nutrients and other contaminants in surface runoff from crop fields. The efficiency of this filtering depends on such characteristics as soils, management, slope and size of the field and buffer, the intended contaminants to be filtered or trapped and intensity of rainfall events. The USDA Natural Resources Conservation Service (NRCS) considers buffers a “Core 4” practice that has “conservation impact and can be implemented on almost every farm.” The Minnesota NRCS has specific designs for buffers that are between 30 and 160 feet, depending on resource concerns and site characteristics.
Here’s a partial rundown of why buffers are one go-to practice for cleaning up water in rural areas:
- A Nebraska study found that doubling the width of a buffer from a little less than 25 feet to almost 50 feet significantly increased infiltration and dilution of runoff. Increasing the width of the buffer cut the amount of nitrogen and total dissolved phosphorous making its way to the water by 15 percent, and the amount of total suspended solids — defined as the amount of solids in water that can be trapped by a filter — by 6 percent. Volume of outflow was also reduced significantly with increased width, contributing to the reduction of contaminants making their way to the water.
- An Environmental Protection Agency review found that when buffers are at least 164 feet in width, nitrogen removal efficiency is consistently around 75 percent. Efficiency was greater with subsurface than surface flow and with forested versus grassed buffers.
- Researchers in Iowa simulated various buffer widths based on different slopes (2 percent and 10 percent) and soils (silty clay loam or fine sandy loam) and found that the width of filter strip required to achieve a given level of trapping efficiency is variable. Filter strips as narrow as 13 feet were estimated to trap nearly 100 percent of the incoming material in some cases, while 98-foot strips trapped only 10 percent of the load in other situations. Site conditions also influence the relationship between width and trapping efficiency. For example, a filter strip on coarse-textured soil below a disked corn field yielded substantially higher trapping efficiencies for sediment and water than an otherwise similar strip on fine-textured soil below a chisel-plowed corn field. In a follow-up study, researchers found that when water flow off a field is concentrated, the filter needs to be wider at that point to serve as an effective filter.
- In central Iowa, researchers found that planting just 10 percent to 20 percent of a no-till, corn or soybean field to strips of native prairie cut sediment, total nitrogen and total phosphorous losses by 90 percent. The strips varied in width from 10 to 33 foot wide on the contours and were 121 to 255 feet wide at the foot of the 6 percent to 10 percent slopes studied. The plant density, stiffness of the stems and deep roots helped make these strips effective even when more than nine inches of rain fell in the area during a three-day period in 2010. The strips’ ability to handle heavy precipitation events is key, given that we are experiencing more intense storms that ever in Minnesota and across the Midwest, especially in the spring when row crops are not covering the soil.
- Conventional filter strips will not reduce tile line flow if the line simply runs under the buffer to a waterway. However, a saturated buffer, where applicable, may enable effective reduction of nitrogen loss by diverting the tile line to flow through the buffer. A study in Iowa with 60-foot strips showed an average nitrate-N concentration reduction of up to 100 percent passing through a buffer root zone. Cost-share funds for such a practice may be available from the Natural Resources Conservation Service.
In short, buffers, depending on characteristics of the field and the buffer, landowner/farmer goals, applicable regulations and voluntary conservation program requirements, may help landowners:
- Protect water quality by trapping and filtering overland runoff and subsurface flow of water, sediment, nutrients, pesticides and pathogens.
- Provide an alternative for marginal, flood-prone cropland along creeks and streams.
- Eliminate end rows and provide turn areas for machinery.
- Reduce downstream flooding.
- Comply with existing drainage ditch laws, shore land rules, and setback requirements for manure application and certain herbicide labels.
- Provide habitat for pollinators and other wildlife.
- Reinforce and strengthen streambanks that can be prone to eroding and slumping into the water.
The Buffer Initiative is Not ‘One-Size-Fits-All’
The Initiative has been mislabeled as being a “one-size-fits-all” requirement. However, a close reading shows this proposal is actually quite flexible, and fits with LSP farmer-member desires to see conservation programs that allow farmers to adopt water-friendly measures that fit individual situations. A Department of Natural Resources fact sheet on the Buffer Initiative makes it clear that flexibility is built into this proposal: “…the initiative allows landowners to use alternative conservation measures that would provide the equivalent water quality, soil stabilization and habitat benefits.” A sample list of such alternative practices can be found here.
Farmers and landowners would be able to work with their local Soil and Water Conservation District or NRCS office to develop a water-friendly system that is practical for each individual farm and gets the most environmental bang for the buck. Practices farmers already have in place, such as cover cropping, reduced tillage, water and sediment control basins, grassed waterways, organic management, managed rotational grazing, etc., would be taken into account.
And taking such options into consideration can play a key role in protecting our water. For example, scientists from the USDA Agricultural Research Service, the University of Minnesota and Iowa State University found that diversifying a typical corn-soybean rotation with small grains and alfalfa plantings reduced synthetic nitrogen use by 80 to 86 percent compared to the conventional system. After several years, good weed control was possible in the more diverse systems, even though herbicide use was slashed by 86 to 90 percent. This meant potential herbicide-related freshwater toxicity associated with the diverse rotations was eventually 200 times lower compared to the conventional system. Additionally, a more diverse rotation puts more living roots in the ground for longer portions of the year. That means the land is more likely to withstand severe weather events without losing topsoil or crops. Finally, the diverse rotations produced competitive yields and similar—in some cases slightly higher—profits compared to their conventional counterparts.
Making Buffers Pay
The Buffer Initiative has also been labeled a “taking” by opponents because of the concern that it allows the government to force a farmer to replace cash crop acres with “non-productive” land. However, buffers can be an economic benefit on acres that often doesn’t have the best return on investment. Waterlogged land that’s prone to frequent flooding is often less profitable than higher quality fields. If streams and banks are not adequately protected on one farm, it may cause damage to a neighbor’s conservation efforts, as well as increase public costs downstream.
And, there are public resources to assist with the cost of putting in buffers. The Continuous Conservation Reserve Program (CCRP) is a voluntary program in which the Farm Service Agency provides participants with rental payments and cost-share assistance to establish long-term, resource-conserving vegetative cover on eligible land. Farmers and/or landowners may enroll such land at any time, rather than waiting for specific sign-up periods. Unlike general sign-ups, there is no bidding and ranking; the land is enrolled automatically if it meets the eligibility criteria. At the end of a contract, landowners have the option of re-enrolling.
One CCRP practice is the CP-21 filter strip, which can be a way for a farmer to get paid to have a buffer between crop fields and water. To be eligible for such a filter strip payment, a farmer or landowner mush have owned or operated the land for at least 12 months and the land must have been planted in an agricultural commodity for four of the previous six years.
There are other federal, state and local programs that provide financial and technical support to landowners who are implementing buffers or alternative water quality practices. Detailed descriptions of these programs are available here.
But even if a farmer is not enrolled in CCRP, the buffer initiative allows haying or grazing and the harvest of perennials for biofuels, which can produce direct income for a working farm. One option for getting economic benefits from buffer strips is to utilize management intensive rotational grazing of cattle and other livestock, which can also be done through contract grazing with a neighbor. Farmers in Minnesota and other Midwestern states have had good results grazing streambanks for short, controlled periods of time, which reduces the presence of invasive species and strengthens grasses and other deep-rooted plants that hold soil in place while filtering out pollutants. This has resulted in more stable streambanks, less sedimentation and overall better water quality. Conservation groups like Trout Unlimited have supported farmers utilizing rotational grazing of streambanks as a way to maintain the health of stream rehabilitation projects.
The buffer initiative is an opportunity for farmers to take a proactive approach to improving water quality for the entire state while making a more efficient use of some of their more marginal acres. Buffers are not the only approach needed to protect and restore Minnesota’s streams, rivers and lakes, but they can provide farmers an opportunity to utilize creativity and ingenuity in the ongoing effort to reach a goal that benefits all of us: cleaner water. LSP strongly believes Governor Dayton’s Buffer Initiative is a step in the right direction.
George Boody is the executive director of the Land Stewardship Project. He can be reached at email@example.com or 612-722-6377.
The buffer initiative is a good start. However, not all surface water ends up flowing over the buffer. On the majority of tile drained agricultural lands, the discharge goes directly into the nearby ditch/flowing stream without filtering. Is there a way to provide a buffer for these polluted waters(fertlizer, insecticide, pesticide, other)?