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Farming is an integral part of the Minnesota story, as many Swedes, Germans and Norwegians came to the rich southern and western river valleys to carve out a life for themselves.
Fertilizers catalyzed the increased capacity of farms. A survey of U.S. crop production indicates that yields would drop by up to 60% if fertilizers were removed. Nitrogen-based fertilizer efficiency has increased — 35% in the past 25 years.
But there are costs. According to the Friends of the Mississippi River, Minnesota farm operations overapply 100,000 tons worth of nitrate fertilizer a year. This has resulted in mass nitrogen contamination in public and private wells. Nitrate concentrations in the metro Mississippi River have increased by 44% since 1976.
Nitrogen contamination is linked to methemoglobinemia, a human health problem that alters how oxygen is carried, which causes headaches, stomach cramps and vomiting. Nitrogen contamination also causes environmental problems, making the water unsuitable for drinking and stimulating rapid algae growth. Minnesota has set a goal to decrease nitrogen contamination in surface water by 45% by 2040. If Minnesota follows existing fertilizer regulations, however, we will reduce surface water contamination by just 15% by 2040.
This gap between Minnesota’s goals and the existing regulations is easily explained. Current regulations attempt to curb negative environmental impacts, but they are primarily meant to maximize agricultural profit. According to researchers from the University of Minnesota, these regulations follow the maximum return to nitrogen rate. This rate encourages farmers to allocate fertilizer slightly above what meets the threshold for efficiency. This results in many farms over-applying nitrogen, resulting in spillover into rivers and groundwater.
Spillover rates are only increasing. Climate change-induced precipitation changes — increased rainfall in fewer rain events — are wiping out slight efficiency gains from improvements in fertilizer technology and existing regulations. According to the Minnesota Pollution Control Agency, since 1895, Minnesota’s total annual rainfall has increased by 3.4 inches of rain on average. In turn, this is increasing erosion, causing flooding, and wiping out crops and infrastructure. Most farms sit alongside major river valleys due to the rich soil caused by river sediments, but that means they are at an increased risk of flooding. Last spring, water levels crossed major flood thresholds around the state and sat high for close to three weeks. With this flooding came mass spillover from sitting fertilizer on farms into Minnesota’s water system, causing unhealthy nitrogen levels in the water.
Significant rain events are likely to increase in the coming years, which means we need to find and implement solutions to preserve water quality. Solutions include managing livestock access, implementing conservation tillage, and improving drainage systems.
Two of the cheapest and most effective solutions, however, are cover crops and buffer zones.
Plant ground cover, in the form of cover crops or perennial species, is crucial to sustainable farming in this changing climate. These will negate the risk of erosion on barren farmland that otherwise are prime locations for spillover. An Iowa State agronomist found that planting perennial grasses in midwestern farmland could decrease nitrogen runoff by 70%; this conclusion closely mirrors the findings of the Iowa Nutrient Reduction Strategy. Cover crops can also be planted early in the season and take in many nutrients that have sat throughout the winter but would be washed away in the spring. They are also reasonably cheap at an average cost of $20 per acre.
Another solution is the implementation of thorough buffers and vegetative filter strips, which intercept runoff and shallow groundwater entering the water system. They then filter this runoff and catch much of the nitrogen and phosphorous. According to a team led by Iowa State researchers, this is the most effective way to stop particulate pollutants, such as dirt, and limit the number of soluble pollutants. They are also affordable. Gov. Mark Dayton signed a law to mandate buffer strips in 2015. The Minnesota Board of Water and Soil Resources has recorded nearly 100% compliance with the law, compared to just 87.2% back in 2017. There is still work left to do, but the widespread adoption of this legislation has been encouraging.
These solutions have to be implemented soon. Climate change is accelerating, and if we do not adapt, there could be serious health and environmental consequences for the Minnesotan communities we call home. We must encourage farmers to implement these practices as soon as possible, but Minnesota legislators need to get to work on reforming fertilizer practices.
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