- - Soil Health

Why Your Neighborhood Matters To Your Soil

While fertilizer is used as an essential tool to ensure plants have sufficient nitrogen, phosphorus, and potassium, the majority of nutrients from its application don’t make it to the crops themselves. According to the U.S. Environmental Protection Agency, agriculture is the largest contributor to impaired water quality. And much of this is a result of fertilizer leaching out from the soil and flowing through local waterways like lakes, bays, and streams—taking nutrients with it.

“I live here,” Roy Bardole, a soybean farmer in Iowa told the EPA, “If I hurt my water supplies, then I ruin my business. Moreover, if I allow nitrogen and phosphorus runoff to hurt my neighbors’ water, then I’ve hurt their livelihoods too.”

Fertilizer runoff causes eutrophication, which is when water becomes over-enriched with nutrients that cause excess growth of plants and algae. It costs the U.S. an estimated $2.2 billion per year, with $813 million of that devoted to drinking water treatment, specifically.

For the past several years, Lake Erie has been plagued by high growth of cyanobacteria, better known as blue-green algae. In March, the Ohio Environmental Protection Agency (EPA) designated the Western part of Lake Erie as impaired for aquatic life, public drinking water, human health, and recreation. Toxins from the algae kill off plants and animals in the water, make humans sick, and make it difficult for entire regions to source clean water.

And Lake Erie isn’t the only waterway in trouble. Already this Spring, blooms have been spotted in New York’s Suffolk County and in lakes near Olympia, Washington. Researchers and scientists attribute the growth in the number of blue-green algae incidents to soil fertilizer runoff from farms near the lake.

In these regions with many farms, agricultural runoff contributes to what’s called nonpoint source pollution, meaning that the contamination doesn’t come from a single known polluter like a factory. Rather, it’s the result of pollution from a variety of sources that moves around an area because of rainfall, seepage, erosion, or other physical factors. In other words, for farmers worried about pollutants—and polluting—location matters.

For farmers worried about pollutants—and polluting—location matters.

The Effect on Farms

Globally, 70 percent of freshwater goes into agriculture, according to the World Bank. Farms depend on water. And when that water carries excess nutrients to fields, it affects farmers long before it causes an algal bloom somewhere on the coast. Across the U.S., 30 percent of small streams have high levels of nitrogen or phosphorus, according to the EPA.

In heavily agricultural areas, water runoff can carry various farms’ excess fertilizer across large swaths of land. Especially after heavy rain or snow melts, runoff can seep out of soil and pollute groundwater in areas beyond individual farms. Depending on the nature of the pollution, farms can experience problems in the water they use for irrigation, as well.

Some municipalities have worked together to create filtration systems for drinking or irrigation, sometimes prodded or funded by federal or state-wide regulations on groundwater for limits on nitrates and phosphates. But, in some farming towns—like Pretty Prairie, Kansas, where decades of runoff has led to water so contaminated with nitrate that it’s not safe to drink—no solutions have been put into place. That deteriorates the quality of life in regions that depend on agriculture even if the fields are okay, because the contaminated water is not safe to drink. Nitrate, in particular, is associated with higher incidence of thyroid problems and cancer for populations in the watershed.

When water carries excess nutrients to fields, it affects farmers long before it causes an algal bloom somewhere on the coast.

Good Neighbors Have Less Runoff

Fertilizer increases harvest yields at area farms, but water pollution can devastate those same yields at those same farms. So it’s in the best interest of all members of an agricultural community to consider practices that reduce the oversupply of nutrients, which ultimately find their way into groundwater.

Several measures can be implemented to prevent over-fertilization and runoff.

  • Constant testing for nutrient levels. By helping farmers apply the right amount of fertilizer necessary to crops, this monitoring is beneficial to the budget as well as to the environment.
  • Watching the weather. Fertilizer applied just before a rainfall or snowmelt is most likely to wash away. Likewise, accurate estimates for mid-season fertilizer application have historically been harder for farmers to make, and overapplication is more frequent mid-season than in the beginning of the planting season. In Nebraska, regulations created in the 1980s banned fall and winter application of nitrogen fertilizers, which led to a 20-percent reduction in the amount of nitrate in groundwater.
  • Cover crops. After crops such as corn and soybeans are harvested, their fields can lay barren until the next season. By planting additional crops to cover the soil, farmers can curtail the flow of runoff caused by precipitation. Grasses such as cereal rye and ryegrass absorb extra nitrogen in the soil by converting nitrogen into proteins and fixing nitrogen with legumes. Bardole, the soybean farmer, found that planting cover crops and leaving remnants of last season’s harvest in the fields helped to stabilize the soil and reduce future runoff.
  • Monitoring irrigation. Overwatering can change the soil’s acidity and Cation Exchange Capability, which in turn could affect crop growth. Variable rate irrigation is an advance that allows water to be applied to precise locations in precise amounts, determined by sensor readings, known soil types, or crop needs. For Bardole, monitoring water use has been the single most important measure for his farm’s economic success and environmental stewardship, he said.
  • Erosion reduction reduces both nutrient loss and runoff. One erosion control measure is critical area seeding, which plants grass on bare soils to prevent erosion. In 2016, New York state seeded 733 acres of bare soil under its Soil & Water Conservation Districts Program.

Can Agriculture Slow the Flow of Fertilizer Runoff?

Large-scale projects have also been implemented to help curb runoff. The Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, created in 1997, coordinates multistate activities to reduce the size and length of the hypoxic zone in the Gulf by reducing soil nutrient runoff. The zone itself is an area of low oxygen where life is unsustainable. Its 2008 Action Plan required 12 states to create their own strategies for preventing runoff, also calling for reassessments every five years to monitor progress.

Similar plans are in place in other states where waterways have suffered, like Ohio, where a task force aims to track and reduce phosphorus runoff. The EPA, the U.S. Department of Agriculture, and individual states have dozens of programs, suggestions, and incentives to help farmers manage their runoff.

For Bardole, practicing no-till, leaving vegetable matter and remnants of corn and soybean plants in the field after harvesting, planting cover crops, and leaving buffers for streams has helped stabilize the farm’s soil and prevent runoff from damaging the waterways in the region. While these practice help out his neighborhood, they also reduce the farm’s need for fertilizer, and Bardole has been able to cut fertilizer application from 240 pounds of nitrogen per acre to about 140 pounds, all while keeping production at the same level.

“I’m not being noble,” he said. “It’s just a fact that bad water management on our land means a rough year and an uncertain future for Bardole & Sons.”