Researchers at the University of Massachusetts Amherst have used remote sensing to investigate farmland erosion in the Corn Belt region of the Midwestern United States. The study revealed that out of nearly 100 million acres of land that make up the Corn Belt, more than one third has completely lost its carbon-rich topsoil.
The findings indicate that the extent of farmland erosion in the Midwest haa been substantially underestimated by the U.S. Department of Agriculture.
The A-horizon is the upper portion of the soil that is rich in organic matter, which is critical for plant growth because of its water and nutrient retention properties.
Led by graduate student Evan Thaler, the UMass Amherst team analyzed satellite imagery to map areas in agricultural fields in the Corn Belt that have no remaining A-horizon soil.
By combining the satellite measurements across the Corn Belt with high-resolution elevation data, the experts could reveal the true magnitude of erosion.
Productive agricultural soils are critically needed to produce food for a growing global population. However, farmland erosion diminishes soil quality and reduces crop yields.
Thaler and his colleagues estimate that erosion of the A-horizon has reduced corn and soybean yields by about 6 percent. This equates tip nearly $3 billion in annual economic losses for farmers across the Midwest.
The analysis showed that A-horizon has been lost primarily on hilltops and ridgelines. This indicates that tillage erosion, or the downslope movement of soil by repeated plowing, is a major driver of soil loss in the Midwest.
According to the researchers, the study highlights an urgent need to include tillage erosion in the soil erosion models that are used in the Unites States, as well as the need to incentivize adoption of no-till farming methods.
The research also suggests that erosion has removed nearly 1.5 petagrams of carbon from hillslopes. The experts said that switching from intensive conventional agricultural practices to soil-regenerative practices has potential to sequester carbon dioxide from the atmosphere while restoring soil productivity.
The study is published in the journal Proceedings of the National Academy of Sciences.