-Farm News photo by Darcy Dougherty Maulsby
Ever since the blizzard that hit many parts of Iowa right before Christmas 2022, snirt (a mix of snow and dirt) has been a common sight, from ditches to yards.

Remember that blizzard that hit many parts of Iowa right before Christmas 2022? Those sustained, howling winds are gone, but evidence of the damage remains in the form of snirt (a mix of snow and dirt), from ditches to yards.

“Erosion happens a lot faster when intense weather events occur,” said Angie Rieck-Hinz, an Iowa State University Extension field agronomist in north-central Iowa. “Soil degradation is happening in Iowa, and we need to slow this process down.”

There is a cost to soil erosion — and it can be high.

Ever wonder how much money is in the ditch in the form of snirt?

So did Jodi DeJong-Hughes, a regional educator with the University of Minnesota Extension who specializes in tillage systems, soil compaction and improving soil health. Nearly a decade ago, DeJong-Hughes sampled snirt in the ditch along state Highway 40 in western Minnesota. Laboratory analysis and math revealed that on a per-acre basis, fields were losing $82 to $96 worth of nutrients (including nitrogen, phosphorus and potassium).

-Farm News photo by Darcy Dougherty Maulsby
Options for reducing tillage to protect the soil can include strip tillage, shown here in a north-central Iowa field. It can take three to five years to see results from reduced tillage, said Angie Rieck-Hinz, an Iowa State University (ISU) Extension field agronomist. It takes time for soil structure to change so it’s more resilient and less prone to erosion.

Given today’s fertilizer prices, those dollar amounts would be substantially higher, Rieck-Hinz said.

Those numbers don’t tell the whole story, though. The snirt was not analyzed for other valuable plant minerals or organic matter content in the snirt. Even if snirt ends up in a different part of the field, rather than a road ditch or yard, it affects the field’s productivity, Rieck-Hinz said.

Topsoil that’s eroded off a slope has a much bigger negative impact on crop production than the accumulation of eroded topsoil on downslope areas, which likely have more-than-adequate topsoil to produce crops.

If that weren’t enough, soil that’s eroded by wind or water can also end up in Iowa’s waterways, where it adds sediment and excess nutrients (including phosphorus) that degrade water quality.

Step one: Identify goals for the land

While the amount of soil erosion has decreased in the United States and Iowa in the past few decades, various researchers say it remains a serious problem.

University of Massachusetts-Amherst researchers have conducted high-resolution, topographic surveys of Midwestern soil. Their results, which the university reported in 2021, indicated that soil thickness on hilltops in the Midwest had declined at an average rate of nearly 2 millimeters a year during the past 150 years. The historical erosion rates exceed predictions of present-day erosion rates from national soil erosion assessments and levels considered tolerable by the U.S. Department of Agriculture (USDA).

It can be hard to envision soil erosion from this perspective.

“Walk your fields in the spring to see what has happened,” Rieck-Hinz said. “Right now, you can see all the soil in road ditches from the blizzard before Christmas. When we had several inches of rain in late February, we could see sheet and rill erosion in unprotected fields, because the soil was still frozen below the top 3 inches. When the water can’t infiltrate, it has to go somewhere.”

Lighter colored soils are a sign that sheet erosion (from the movement of water) has taken its toll. Rill erosion occurs during heavy rains, when flowing surface water cuts small, shallow channels into the soil.

Wind erosion is also a challenge in Iowa, especially when dry weather conditions and excessive tillage practically turn the soil into powder. That soil easily blows away, especially when fields are bare, Rieck-Hinz said.

Fortunately, there are a number of ways to help manage soil erosion, from reducing tillage to growing cover crops to planting shelterbelts of trees that function as a windbreak.

“We have seen a movement toward less tillage through strip-tillage and no-till systems in Iowa, and we have also seen a slow adoption of cover crops,” Rieck-Hinz said.

There’s no silver bullet, however, when it comes to managing soil erosion.

“This needs to be a systems approach,” Rieck-Hinz said. “The first step is always identifying goals. Is your goal to protect the soil? Improve water quality? Get higher yields? Reduce labor? Add more conservation? Enhance nutrient cycling in your field? If you don’t know what your goals are, how can you measure results?”

Once you determine your goals, this will help you fine-tune practical strategies to reach these goals. If you want to plant cover covers to control soil erosion, for example, oats aren’t the best choice, because they winter kill, Rieck-Hinz said.

After you implement practical strategies to reach the goals you’ve set, it’s important to measure results.

Soil health tests can provide specific, measurable data. So can bulk density tests, which reflect soil compaction, while infiltration tests can measure the soil’s capacity for water and air infiltration.

Other assessments may be less scientific but are still worthwhile, Rieck-Hinz said.

“Are you seeing less runoff, due to better soil structure that allows for better water infiltration? When you dig in your field, are you seeing more earthworms in your soil?”

Finally, have realistic expectations. “If you want to reduce tillage to protect the soil, it can take three to five years to see results,” Rieck-Hinz said. “It takes time for your soil structure to change so it’s more resilient and less prone to erosion.”

Opening the lines of tenant-landlord communication

While implementing soil conservation practices can be fairly direct when the farmer is the landowner, what about landlord-tenant relationships?

“If you’re a tenant, invite your landlord to a field day to see the types of farming practices you’d like to try,” Rieck-Hinz said.

If the landlord doesn’t live nearby, the tenant can provide a yearly, written summary and photos of the farm to show how he or she is managing the land. Also, invite the landlord to the farm to see what’s going on, and ask the landlord about his or her goals for the land.

“We encourage landowners who want to encourage more conservation to incentivize tenants,” Rieck-Hinz said. “Maybe lower their cash rent so they have more financial resources to seed cover crops, for example, or give them a multi-year lease, rather than a one-year lease.”

Time can be an asset or an enemy when it comes to protecting Iowa’s precious topsoil. This is easy to forget, since soil erosion is a gradual process.

The lessons of history are clear, however.

“Soil deterioration and impaired water quality due to erosion and surface runoff have become severe problems worldwide,” according to the report “Soil Erosion: An Agricultural Production Challenge,” which is available online from ISU Extension. “The problem may become so severe that the land can no longer be cultivated and must be abandoned. Many agricultural civilizations have declined due to land and natural resource mismanagement, and the history of such civilizations is a good reminder to protect our natural resources.” Don’t wait, Rieck-Hinz added.

“Iowans brag about their soil, and rightfully so, but this is a resource that needs more attention to continue to support our crop production systems.”