Farming is reliant on soil to produce food. The main long-term threat to the soil is erosion by wind and water.
Wind erosion is a soil health thief. In both sandy and fine-grained silt soils of Eastern Washington, wind erosion lifts, sifts, and then carries away the best part of the soil. Lost are the tiny particles of clay and silt with the organic matter that is stuck to them. It also removes light, sand-sized particles of organic matter. It leaves the sand. If the soil is your cupcake, wind erosion eats the frosting.
How does this happen?
In the dry Columbia Basin of Central Washington state, wind erosion is the primary threat and is made worse by the local soil conditions. On the eastern side of the Cascade mountains, low rainfall produces sparse vegetation. In turn, this results in native soils with low soil organic matter levels. Soil organic matter is important in aggregation, where tiny soil particles are stuck together in crumb-like structures called aggregates. With low soil organic matter levels, soil particles are left loose, unaggregated. This is compounded by the sandy, wind erosion-prone soils that are common in the Columbia Basin of Washington.
Besides soils prone to wind erosion, farmers must deal with the timing of windstorms. The region has distinctly wet winters and dry summers. Between the wet and dry seasons, each fall and spring, windstorms are common. This timing is unfortunate for farmers. Spring winds can occur before newly planted crops provide much protection from the wind. The harvest of crops like potatoes and onions leave the soil with little protection against Fall winds. This combination of high winds and dry, loose, sandy soils make wind erosion a twice-yearly risk for farmers in Eastern Washington.
When the wind moves the soil, there is dust. Dust storms reduce visibility for drivers and can cause serious accidents. Dust can also cause respiratory health problems, both locally and in distant populations. By themselves, these problems are enough for farmers to take wind erosion control seriously, but they must also worry about what the wind erosion does to their soils.
Making matters worse, erosion removes these particles from the soil’s surface where important processes take place. At the soil surface, water and air enter the soil, seeds germinate, seedlings emerge, and biological activity is high. Without fine particles and organic matter, the soil cannot form aggregates. The reduced ability to form soil aggregates reduces water and air intake and increases runoff from irrigation or rain. Surface crusting impedes seedlings. Without aggregates, the soil is more susceptible to further loss by wind erosion, beginning what can be a downward cycle of soil degradation. In this way, wind erosion’s selective thievery not only steals current soil health, but future soil health too.
So, what can farmers do?
Just as homeowners protect their homes from theft, farmers protect their soils from wind erosion. The key is keeping the soil covered as much as possible with either dead plant residues or living plants. Through reduced tillage and specialized planting and harvesting equipment, farmers can manage their system to provide a protective cover of residues from harvested crops. They can intersperse high residue crops like corn or wheat with low residue vegetables like potatoes and onions. After harvest, they can protect the soil with living plants by planting cover crops. And when needed and available, farmers can use irrigation to reduce wind erosion; wet soils don’t blow.
How are farmers doing?
In the Columbia Basin of Washington, irrigation has allowed increased crop growth, which leaves larger amounts of crop residues on the soil. This has increased soil organic matter levels, making the soil more resistant to wind erosion. Herbicides are a useful tool, controlling weeds without tillage, and thereby leaving more protective crop residues. Advances in planting and harvest machinery have also played a role. Compared to when the sagebrush was first broken out for farming, farmers have reduced wind erosion significantly.
However, there remain challenges. Because farmers fill up the growing season with cash crops, sometimes growing two crops over the summer, it is difficult to establish cover crops in time for them to grow a protective canopy. Wind erosion of farm roads, dusty from constant use during the dry summer, is a problem with no practical solutions. Root crops, which require extensive tillage for harvest can leave erosion-prone soil conditions, especially when harvested late.
Wind erosion is a natural process in Eastern Washington. The Palouse region, east of the Columbia Basin, has deep loess soils deposited by winds over the millennia. So, while farming, especially the bare soil farming of earlier years, increased wind erosion, the conditions for wind erosion were there long before. Winds will continue to blow the soil as long as there are dry soils and windstorms, but farmers can minimize wind erosion on their farms using all available tools.
Answered by Andrew McGuire, Washington State University
Dr. McGuire presented at the 2020 Sustainable Conference offered by the American Society of Agronomy; to listen visit here.
About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world’s food supply while protecting our environment. We work at universities, government research facilities, and private businesses across the United States and the world.