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posted by janrinok on Saturday January 21 2023, @07:27PM   Printer-friendly
from the dishing-the-dirt dept.

First precise calculation of the pre-agricultural rate of erosion across the Midwestern U.S., thanks to exploding stars:

In a discovery that has repercussions for everything from domestic agricultural policy to global food security and the plans to mitigate climate change, researchers at the University of Massachusetts recently announced that the rate of soil erosion in the Midwestern US is 10 to 1,000 times greater than pre-agricultural erosion rates. These newly discovered pre-agricultural rates, which reflect the rate at which soils form, are orders of magnitude lower than the upper allowable limit of erosion set by the U.S. Department of Agriculture (USDA).

The study, which appears in the journal Geology, makes use of a rare element, beryllium-10, or 10Be, that occurs when stars in the Milky Way explode and send high-energy particles, called cosmic rays, rocketing toward Earth. When this galactic shrapnel slams into the Earth's crust, it splits oxygen in the soil apart, leaving tiny trace amounts of 10Be, which can be used to precisely determine average erosion rates over the span of thousands to millions of years.

[...] The numbers are not encouraging. "Our median pre-agricultural erosion rate across all the sites we sampled is 0.04 mm per year," says Larsen. Any modern-day erosion rate higher than that number means that soil is disappearing faster than it is accumulating.

Unfortunately, the USDA's current limit for erosion is 1 mm per year—twenty-five times greater than the average rate Larsen's team found. And some sites are experiencing far greater erosion, disappearing at 1,000 times the natural rate. This means that the USDA's current guidelines will inevitably lead to rapid loss of topsoil.

[...] Yet, there's no reason to despair. "There are agricultural practices, such as no-till farming, that we know how to do and we know greatly reduce erosion," says Quarrier. "The key is to reduce our current erosion rates to natural levels," adds Larsen.

Journal Reference:
Caroline L. Quarrier, Jeffrey S. Kwang, Brendon J. Quirk, et al.; Pre-agricultural soil erosion rates in the midwestern United States. Geology 2022;; 51 (1): 44–48. doi: https://doi.org/10.1130/G50667.1


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  • (Score: 4, Interesting) by pdfernhout on Sunday January 22 2023, @01:39AM

    by pdfernhout (5984) on Sunday January 22 2023, @01:39AM (#1287984) Homepage

    https://e360.yale.edu/features/how-the-loss-of-soil-is-sacrificing-americas-natural-heritage [yale.edu]
    "You hear many different numbers regarding that black Iowa soil. It’s often repeated that the topsoil — the nutrient-rich A horizon — was some 14 to 16 inches deep when the prairie was first broken, a fantastic depth of fertility rivaled only by some regions in the Ukraine. By the mid-1970s — roughly a century after the prairie was broken — it was reported that, in places, half of that topsoil had already been lost to erosion from wind and runoff. There was a lot of talk about soil conservation, of course — about contour plowing and set-aside programs that paid farmers to keep marginal land out of cultivation. Yet year by year, the soil loss went on. ... The number [scientists in a new study using satellite imagery] arrived at is shocking. “We predict,” they wrote, “[that] the A-horizon has been completely removed from 35±11% of the cultivated area of the Corn Belt.” Plus or minus 11 percent is a large range of uncertainty. But its meaning is plain. At best, 24 percent of the topsoil in the Corn Belt has been completely removed by farming. At worst, 46 percent has been lost."

    I had read somewhere (Wes Jackson?) that big parts of the Midwest had gone from six feet of topsoil before farming and were now six inches, but perhaps that is an exaggeration compared to the above?

    How to rebuild fertile topsoil by grinding up rock:
    https://www.remineralize.org/ [remineralize.org]
    "Remineralization utilizes finely ground rock dust and sea-based minerals to restore soils and forests, produce higher yields and more nutritious food, and store carbon in soils to stabilize the climate."

    --
    The biggest challenge of the 21st century: the irony of technologies of abundance used by scarcity-minded people.
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