Stop Erosion in the Bud!

Soil erosion is still the most serious issue in our country. With 60% of Pennsylvania cropland being highly erodible it requires constant attention. The most important cause of topsoil loss is tillage erosion – hence the importance of no-till farming for sustainable agriculture.

Crop yields continue to improve so what's the big deal about soil erosion? That is a common way of thinking. However, buried in there is the fact that if you had not lost so much topsoil, your yields would be better still, and you would not have to use so much fertilizer. A 2005 study compared corn yields of Iowa soils that had lost varying amounts of topsoil. The study found that corn yield was reduced approximately 16 bu/A if topsoil thickness was reduced from 15 to 0 inches on loess soils, and 26 bu/A on till-derived soils. The latter would probably better reflect typical yield reductions on Pennsylvania soils. Of course, topsoil loss is not uniform throughout a field – on hillcrests no topsoil may be left while in the bottom of the field topsoil depth may have increased due to deposition. But yield losses would progressively increase if the areas without topsoil, or that have reduced topsoil depth, would grow. It is therefore important to reduce this phenomenon. Research has shown that tillage erosion is the primary culprit of topsoil loss in undulating landscapes. Tillage erosion is the mere translocation of soil by gravity when you till a soil. It happens with any type of tillage, although depth, speed, and direction of travel also play a role. This is why the practice of no-tillage is so important to guarantee productivity of our soils into the future. Tillage erosion goes hand-in-hand with water erosion – which is the washing away of the soil by water. The loosened soil is moved downhill by tillage, aided by sheet and rill erosion, and at the bottom of the field where runoff is greatest, the soil will be moved off the field. However, much soil moved by tillage erosion actually never leaves the field but the spots without topsoil continue to grow. The matter is of grave concern for the sustainability of American agriculture. University of Massachusetts researchers recently published a study where they evaluated topsoil loss in the Corn Belt using remote sensing. The work was published in the Proceedings of the National Academy of Sciences. They showed that 35% of Corn Belt cropland has lost the entire A horizon, far exceeding past estimates of the damages of soil erosion. The estimated yield losses were 6% per year, with an annual loss of $2.8 billion. As the authors point out, only 15% of the heart of the Corn Belt is farmed with no-till for three consecutive years. By using continuous no-till, tillage erosion can be eliminated.

Referenced studies

T.E. Fenton*, M. Kazemi, M.A. Lauterbach-Barrett, 2005. Erosional impact on organic matter content and productivity of selected Iowa soils. Soil Tillage Res. 82:163-171

Evan A. Thaler, Isaac J. Larsen, and Qian Yu, 2021. The extent of soil loss across the US Corn Belt. Proceedings Nat. Acad. Sci. Vol. 118 No. 8 e1922375118