Nitrogen fertilizer application restrictions on crop ground went into effect in certain areas of Minnesota on Sept. 1, 2020. The Groundwater Protection Rule bans application of most forms of commercial nitrogen fertilizer in the fall and on frozen ground in areas vulnerable to contamination.
The rule aims to minimize potential sources of nitrate pollution in groundwater to protect public health.
Harold Wolle, who grows corn and soybeans in south-central Minnesota, near Madelia, contends most farmers didn't embrace the law but accept it. The Minnesota Corn Growers Association District 2 director says producers, farm organizations and the state worked together to come up with a workable rule that doesn't curtail food production and protects the environment.
"We are certainly cognizant of the effects nitrogen can have on groundwater," Wolle says. "We are committed to being good stewards of the land.
"From that standpoint, there won't be much pushback to this rule," he adds. "Particularly if people can meet the requirements without substantially changing how they operate."
Some farmers inject anhydrous ammonia, a popular corn nitrogen fertilizer, in the fall for the next year's crop. Wolle and his son, Matt, who's taking over the 1,700-acre farming operation, do that on their clay-based soil, which is still allowed. However, they have never fall-applied anhydrous in sandier soil, which the law now forbids.
Wolle asserts the chance of nitrogen loss or leaching in the sandy soil is too great. "It's not a good practice agronomically, nor for (protecting) groundwater."
Soil microbes convert organic nitrogen to nitrite and then nitrate. The speed of conversion depends on several factors, such as temperature (microbes are more active when soil temperatures are 50°F and above) and moisture. Nitrates, which are a major source of water pollution, are highly mobile in the soil and vulnerable to leaching.
The Groundwater Protection Rule's fall nitrogen restrictions target areas the most prone to leaching, which include coarse-textured soils, shallow bedrock or karst geology. It also affects farms in drinking water supply management areas (DWSMA) with high nitrate concentrations.
The state and federal nitrate health limit in drinking water is 10 milligrams per liter. Higher concentrations are a particular health risk to infants and pregnant women, and potentially adults.
Only about 13% of Minnesota's farmland -- mostly in the north-central, southeast and southwest part of the state -- is affected by the rule, explains Larry Gunderson, a supervisor in the Minnesota Department of Agriculture (MDA) Pesticide and Fertilizer Management Division. Roughly the northern third of the state is excluded. The state has 25.5 million acres in farms, U.S. Department of Agriculture data shows.
All of Rod Sommerfield's crop ground, 20 miles north of Rochester, is within the restricted area for fall nitrogen application. The rule won't affect him.
"I tried fall nitrogen once in the 1970s and said, 'This is foolish,'" Sommerfield says. I don't apply fall nitrogen because it's eight months before the plant needs it. We should have done it [rule] 50 years ago."
The rule is also designed to reduce nitrate levels in groundwater before a public well exceeds government health standards. A sliding scale of voluntary and regulatory actions, which includes the use of best-management practices, will be implemented in a DWSMA based on the concentration of nitrate in a well. A local advisory team of farmers, agronomists and community members will make recommendations to the MDA on how best to reduce nitrate levels.
"We've known for quite some time that nitrate levels are high in groundwater in certain parts of the state," Gunderson continues. "Now, we have the blueprint to address it. I would say Minnesota is a leader in this."
Not all fertilizer containing nitrogen is regulated based on farmer input. The rule does not apply to manure. There are exceptions that apply to the spreading of MAP (monoammonium phosphate) and DAP (diammonium phosphate) -- up to a field average of 40 pounds of nitrogen per acre. Exemptions also exist for fertilizing winter grains, wild rice and perennial crops, and to establish pastures.
Gunderson hopes developing the rules with farmers and prior outreach will make implementation easier. Farmers who don't comply with the rule can be fined, but specific penalties weren't available at press time. MDA indicates it will help farmers comply through education before fines occur, though circumstances may dictate otherwise.
"The restrictions don't affect every farmer, but we do encourage (all producers) to follow best-management practices in areas where they can apply nitrogen in the fall," Gunderson says. "That means waiting until soil temperatures are 50°F or less and using other practices that decrease the loss of nitrogen."
Minnesota Buffer Law:
Nitrogen fertilizer restrictions are Minnesota's second regulatory effort to protect the state's water resources.
Five years ago, the state's legislature passed a law requiring perennial vegetative buffer strips of up to 50 feet along lakes, rivers and streams, and 16.5 feet along most drainage ditches. Buffers help filter out phosphorus, nitrogen and sediment before it enters waterways. Visit www.mn.gov/buffer-law for more information and a map of the public waters inventory.
The deadline for implementation on public waters and ditches was Nov. 1, 2017 and Nov. 1, 2018, respectively. Tom Gile, resource conservation section manager for the Minnesota Board of Water and Soil Resources, says compliance exceeds 99%.
"There was some contention early on," Gile adds, referring to farmland taken out of production. "But, generally speaking, landowners are willing to find ways
to make it work."
He estimates 110,000 acres of farmland were converted to buffers. However, buffers can be grazed or harvested for hay.
Buffer widths can be reduced in many cases if farmers implement alternative conservation practices, such as cover crops and conservation tillage. Farmers also have the option to comply with the law by enrolling in the Agriculture Water Quality Certification Program (AWQCP). It's a comprehensive review of farming operations and actions to minimize water-quality impacts.
Harold Wolle enrolled his farm, near Madelia, in the program to reduce the loss of farmland to buffers, which total 20 acres along several drainage ditches. Terraces, waterways and field tile inlets that filter out sediment, among other things, helped him become certified.
"The alternative practices gave us options to work with to comply with the law," he says. "Ultimately, farmers accept it due to their desire to be good stewards of the land."
FOR MORE INFORMATION:
> Minnesota Department of Agriculture Groundwater Protection Rule: www.mda.state.mn.us/nfr
> Follow Matthew Wilde on Twitter @progressivwilde.
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