May 16, 2023
by Sjoerd Duiker
Let's manage our fields so that soil erosion does not degrade the future productivity of our soils or cause harmful effects for our neighbors and the surrounding environment.
A May 1 dust storm in central Illinois caused a vehicle pileup resulting in the deaths of six people and at least 37 injured. The reason: Farmland denudation and soil tillage over large expanses led to wind picking up large quantities of dust, causing devastating effects.
Unfortunately, once the dust settles, we are quick to forget and move on to other things in our rushed society. It would seem that we had learned our lesson in America during the Dust Bowl of the 1930s, but, of course, hardly anyone is alive from those days, and the memories are fading.
Records show that the Dust Bowl was caused by fencerow-to-fencerow tillage and one-crop (wheat) agriculture in a fragile environment that was previously protected by highly diverse prairie vegetation. After several years of drought, wind started to pick up the fine dust of the formerly protected prairie soil, particularly in the area of northern Texas, western Kansas and Oklahoma, and eastern Colorado and New Mexico.
In 1935, it was estimated that 4.35 million acres had lost 849 million tons of soil, a rate of 195 tons per acre. The Soil Conservation Service in 1938 estimated an even higher loss of 490 tons per acre. Later, it was estimated that 10 million acres in the Great Plains area had lost 5 inches of topsoil, and 13.6 million acres lost 2.5 inches. The ravages of soil erosion led to decreased land productivity, reduced land values and hundreds of thousands of environmental refugees.
Even today, millions of acres are in grassland reserves because of Dust Bowl erosion, being unfit for crop production.
We here in Pennsylvania are far from the West, and we typically don’t deal with wind erosion. But the events earlier this month in Illinois, which has a very similar climate to ours, suggest that it could happen here, too.
Nonetheless, we typically deal with other forms of erosion predominantly due to water and tillage. In fact, we distinguish five types of erosion in our farm fields:
Sheet (or interrill) erosion. This is from the impact of raindrops hitting the bare soil surface, dislodging soil particles from the soil matrix.
Rill erosion. Small rivulets are no deeper than 4 inches, typically parallel on the slope until they converge and are easily erased by tillage.
Ephemeral gully erosion. Typically between 4 inches and 1.5-feet deep is still farmable and can be erased with tillage. But it does not disappear in no-till fields. It forms in the same places year after year where runoff concentrates on the landscape. If left unmanaged, it can become a classic gully.
Classic gully erosion. This is more than 1.5-feet deep, not easily farmed across nor erased by tillage. It can lead to land disfigurement and eventually leads to loss of land to production.
Tillage erosion. Downslope movement of soil due to tillage.
The first four are forms of water erosion, while the last one happens due to the physical act of tillage.
The Natural Resources Conservation Service calculates average annual soil loss per acre due to sheet and rill erosion. According to the 2017 Ag Census, the average annual soil loss rate in Pennsylvania was 4.4 tons per acre, which seems low compared to the Dust Bowl estimates but is still above the tolerable soil loss level for many of our soil types.
This estimate also ignores ephemeral and classic gully erosion, and tillage erosion. Further, we must remember that the estimate is just an average rate while most soil erosion by wind or water occurs in erratic, unique events. One highly erosive event, therefore, can easily represent most soil erosion during a whole year or even a whole decade.
When we have significant rainfall at a time when the summer crops are not yet planted or emerged, the fields tend to be unprotected, which is a highly vulnerable situation. And indeed, reports have been coming in of rills and ephemeral gullies, and soil being deposited on roads. These situations need to be addressed for the farmer's own benefit, but also because it poses a threat to other people and the wider environment.
The best way to limit soil erosion by water is to keep soil undisturbed and covered because that dramatically reduces sheet erosion and improves infiltration, thus also reducing other forms of water erosion. Reducing tillage is also essential to limit tillage erosion.
That is why cover crops and no-till, which leave residue on top, are so beneficial to fight soil erosion. It is also beneficial to grow different crops in rotation and break up fields so that growing crops occupy different parts of the landscape.
There are many more practices that can be combined with these practices or used in conjunction with tillage. These practices are especially important for organic producers who cannot control weeds with herbicides. Examples are contour farming, contour strip cropping, terraces and diversions, and grassed waterways.
Take advantage of resources
We are blessed with many resources to help us understand erosion and know-how, and the technologies to deal with it. There are people working at your local soil and water conservation districts, and NRCS, who are available to help you design and implement a soil conservation plan.
Extension educators can also offer expertise to help you succeed with no-till and cover crops. We also have farmer groups such as the Pennsylvania No-Till Alliance that can offer knowhow, expertise and experience implementing these practices.
There are also many employees of agribusinesses who can help you with technologies and advice to conserve soil.
But it takes a decision and determination to address soil erosion, and a realization by you, the farmer, that you can be a steward of the land. Unfortunately, if we don't act ourselves, the government may come in to force us to deal with soil erosion, and that is not a desirable situation.
Duiker is a professor of soil management and applied soil physics at Penn State University.
Source: Penn State Cooperative Extension
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