In the coming weeks, Minnesota is expected to adopt new regulations for agricultural fertilizer use designed to limit water pollution, a move that could also have climate benefits. Synthetic fertilizer use is a major source of agriculture-related greenhouse gas emissions both in Minnesota and nationally.
The new Minnesota regulation is the first time the state has set mandatory regulations on how farmers use commercial fertilizer, in particular nitrogen fertilizer applied primarily for corn production. The Groundwater Protection rule will be signed by Minnesota Department of Agriculture Commissioner Thom Petersen and then by Governor Tim Walz following the end of the state legislative session. It will take effect on January 1, 2020. The Minnesota Department of Agriculture led a two-year process to develop the rule, including more than 17 public meetings around the state. The resulting rule sets a goal of reducing nitrate pollution in Minnesota’s waterways by restricting the use of nitrogen fertilizer.
Under the new rules, farmers are prohibited from applying synthetic fertilizer in the fall and when the ground is frozen. Farmers operating near public wells where nitrate levels exceed state health limits must follow best management practices—these refer to the timing, rate, placement and source of fertilizer application. The practices start as voluntary and become mandatory over time if the nitrate pollution rises. The BMPs are specific to different parts of the state and different crops and can have multiple benefits, including building soil health and increasing a farm’s resilience against extreme weather events.
The rule has shortcomings. It doesn’t require action to protect private wells from nitrate contamination and the pace required of farmers to reduce fertilizer use is too slow, according to a letter signed by nine Minnesota environmental groups. The original rule included those protections, but they were removed after criticism from some agriculture groups.
Synthetic fertilizers are a major source of agriculture-related greenhouse gas emissions, releasing nitrous oxide which is nearly 300 times more potent than carbon dioxide. According to the Minnesota Department of Agriculture, fertilizer purchases by nitrogen units have risen 25 percent in the state from 1990 to 2016. According to the Minnesota Pollution Control Agency, fertilizer-linked GHG emissions have been steadily rising in the state since 2005—from just over 3 million CO2 equivalent tons to nearly 3.6 million CO2 equivalent tons in 2016. The Minnesota data’s rise in agriculture-related emissions mirrors national data from the Environmental Protection Agency published earlier this year, which cited nitrous oxide emissions related to fertilizer as a targeted source of emissions reduction.
Aside from water pollution problems, there are signs that over-applying fertilizer is costing farmers money. A Michigan State University study published last month found that on more than a quarter of Midwest farmland, farmers growing corn and soybeans are over-applying fertilizer to low-yielding acres, and as a result, actually end up losing money. The researchers estimated that the over application of fertilizer in the Midwest was responsible for 6.8 million metric tons of CO2 emissions each year (an estimated .3–1.2 MMT for Minnesota). The study suggests that either removing low-yield acres from production and putting land into conservation programs or perennial grasses could increase profitability. Farmers are feeling pressure to increase production to make up for low (often below cost-of-production) prices. Transitioning low-yielding acres away from heavily fertilized crops could bring climate benefits, as well as reduce chronic over-production that is driving prices down.
In Minnesota, farmers and researchers are exploring new crops, like kernza, that can reduce water pollution, build soil health, and increase farmer income. The Minnesota fertilizer law shows the synergy between policies that support clean water and climate benefits, whether reducing the over-application of fertilizer to planting buffers along waterways to expanding acres of perennial grasses. States across the country should consider policies like the Minnesota fertilizer rule that can provide multiple public benefits.