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Corn Belt Farmland Has Lost a Third of Its Carbon-rich Soil

More than one-third of the Corn Belt in the Midwest – nearly 100 million acres – has completely lost its carbon-rich topsoil, according to University of Massachusetts Amherst research that indicates the U.S. Department of Agricultural has significantly underestimated the true magnitude of farmland erosion.

In a paper published in the Proceedings of the National Academy of Sciences, researchers led by UMass Amherst graduate student Evan Thaler, along with professors Isaac Larsen and Qian Yu in the department of geosciences, developed a method using satellite imagery to map areas in agricultural fields in the Corn Belt of the Midwestern U.S. that have no remaining A-horizon soil. 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. The researchers then used high-resolution elevation data to extrapolate the satellite measurements across the Corn Belt and the true magnitude of erosion.

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Soil Degradation Costs U.S. Corn Farmers a Half-billion Dollars Every Year

One-third of the fertilizer applied to grow corn in the U.S. each year simply compensates for the ongoing loss of soil fertility, leading to more than a half-billion dollars in extra costs to U.S. farmers every year, finds new research from the University of Colorado Boulder published last month in Earth’s Future.

Long-term soil fertility is on the decline in agricultural lands around the world due to salinization, acidification, erosion and the loss of important nutrients in the soil such as nitrogen and phosphorus. Corn farmers in the U.S. offset these losses with nitrogen and phosphorus fertilizers also intended to boost yields, but scientists have never calculated how much of this fertilizer goes into just regaining baseline soil fertility–or how much that costs.

“We know there’s land degradation going on even in U.S. modern agriculture, but it’s really difficult to pin down how much and what impact it has,” said Jason Neff, corresponding author on the paper and director of the Sustainability Innovation Lab at Colorado (SILC).

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