Wind erosion shows itself through duststorms and soil drifts along fencelines. The evidence for water erosion are the channels and deposits from small rills and larger gullies. Farmers and agrologists have traditionally been taught that these are the two main types of erosion. However, within the past three or four years, new research has shown that another type of erosion, tillage erosion, is the largest cause of erosion in many areas using mechanized agriculture. The evidence on the prairies for the severity of tillage erosion are all those eroded knolls. The soil on these knolls was not eroded by water as was traditionally believed but was pushed downhill with every tillage pass.
This likely isn't earth-shattering news to most farmers since anyone who has seen a discer work knows that tillage moves soil. However, in the soil science community, tillage redistribution was considered to be minor compared to water erosion. The only problem with the scientist's view was that largest soil loss from water erosion should occur near the base of the hill and the smallest soil loss should occur on the knoll. This was the opposite of what was observed in the field where the largest soil loss occurs on the knolls. Research on tillage erosion found that not only does tillage move large amounts of soil, it predicts soil redistribution from the tops of hills into the depressions better than any other process.
While tillage erosion does not result in the loss of soil from a field but only redistributes it. The redistribution of soil from the knolls into depressions can result in many agricultural and environmental problems. By moving topsoil with high organic matter levels into the moist depressions, increased mineralization occurs. This results in higher amounts of nitrogen being released in the depressions causing problems with lodging and delayed maturity. In addition, this nitrogen can be lost through leaching or denitrified as nitrous oxide, a powerful greenhouse gas.
Unlike wind and water erosion, tillage erosion does not result in visual clues to the problem. There is no equivalent to a duststorm or field gully. Tillage erosion occurs gradually overtime with no single severe event. Unfortunately, since the problem of tillage erosion is not common knowledge in the agricultural community, it has been easy to ignore.
There are only two ways to control tillage erosion. One is to seed the land down to a perennial forage for hay or pasture. The other is low disturbance direct seeding or zero till. Minimum till practices will reduce but not eliminate the problem. It is fortunate that the conservation tillage practices developed to control wind and water erosion also happened to eliminate the real culprit, tillage.