Where has all the soil gone? Long time passing

Q: What does it mean to say we are losing soil? Where does it go?

wind-erosion-farmfield

An example of wind erosion of soil. Photo courtesy of Albion College Education Blogs, http://teach.albion.edu/jjn10/erosion/

A: You may hear the phrase: “We are losing our soil.” Sounds serious…but how do we lose soil? Where does it go? Soil erosion is the movement of soil by wind or water, and it’s through erosion that soil is “lost.” Organic soils can also be lost through subsidence which happens when an organic soil is drained and its organic matter decomposes.

We lose about 1.7 billion tons of soil per year just from our cropland. That’s a lot, but it’s better than it used to be. Over the past 25 years we have reduced soil erosion by over 40%, mainly by conservation practices such as conservation tillage, terracing, cover crops, and grass waterways. It can take roughly 500 to 1000 years to form one inch of soil, depending on the climate and the material from which soil forms.

With that in mind it’s not hard to see that soil is a non-renewable resource and worth protecting. Since soil is the source of water and nutrients for plants as well as a bioreactor that purifies and filters water, it is crucial to our quality of life.

water-erosion-nrcs

A soil that has been eroded by water. Photo: Natural Resources Conservation Service

Soil erosion occurs when the soil is not protected from the elements. Remove the plants and mulch from mineral soil and things start to happen. Raindrops can break apart the soil making it easier to move it by wind and water. The water’s ability to enter the soil is reduced and more water now can flow over the top of the soil. Unfortunately, water is powerful and can carry away soil particles if it flows overland. Since water flows downhill, that’s where the soil goes once water erosion begins.

Where does the soil end up? It might end up at the bottom of a hill, or it might end up in a river or stream or in the ocean, or it might end up in a reservoir. If soil ends up in reservoir, it limits the space for water and has to be removed by a very expensive process called dredging. If the soil dries out while it’s unprotected, then wind can pick it up and move it downwind.

soil-subsidence-fl

In 1924, this 9-foot concrete post was driven to bedrock at the Everglades Research and Education Center in Florida. This recent photo shows that about 69 inches of soil subsidence has occurred since then.

Organic soils can be drained. When drained, they decompose and this is called subsidence. In the Everglades area of Florida where soils have been drained for agriculture, organic soils have lost as much as five feet or more of their organic matter. Organic soils are preserved by not draining them. Letting them stay saturated with water allows them to continue to build over time.

Soil erosion is expensive. It costs the United States alone about $44 billion per year. Preventing erosion means taking care of the soil. That means protecting it with mulch and plants, not plowing on steep slopes, and maximizing the amount of water that enters the soil while minimizing the water that runs over the soil.

–Answered by Nick Comerford, University of Florida

Have a question for Soils Matter? Post it as a comment below, or email us at soils-matter@soils.org

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12 responses to “Where has all the soil gone? Long time passing

  1. Pingback: natural weather | Richardthurgood's Blog·

  2. I farm out in Central Colorado and a fertilizer company suggested using sulfuric acid to lower my ph. What effects would this have both short and long term on soil microbes, soil health? Is there any cost effective ways to reduce high levels of magnese and magnesium in your soil profile? Thanks.

    • Thank you for your question! We’re trying to line up an expert to answer it right now. I’ll be back in touch as soon as we have the answer.

    • It Depends……on whether the high pH is actually affecting your plant production. try sites like http://www.spectrumanalytic.com/support/library/ff/Mn_Basics.htm
      Ammonium phosphate fertiliser, acid-treated phosphate rock (superphosphate fertiliser ) and iron pyrites all would reduce the pH of your soil but the effect may only be in the small soil area the treatment is applied to. The high pH will be reducing the availability of the manganese of the soil and reducing the chance of it poisoning the plants. High Magnesium can be balanced at the plant-available level with a dose of calcium such as normal limestone or gypsum. Sometimes it may be more productive to cultivate less deep, and rely on loads of fresh organic fertiliser (animal dung or compost ) as an undisturbed top-of-soil layer for the plants to pick out what they want .

  3. soil break and water/wind transport it elsewhere. and the horror are not just that moment but also the lost of fertile soil. physic – chemical – biological support loss.

  4. Hello, I run a blog called Green Infrastructure for Your Community (www.deeproot.com/blog) where we discuss issues around trees, soil, and stormwater. I’d love to reprint this question, as well as one or two others from your blog. Would you be willing to grant me permission to do so? Of course I would be happy to credit Soils Matter and link back to the original post.

  5. Pingback: Where Has All The Soil Gone? | DeepRoot Blog·

  6. Pingback: Peat: Not a “darling” | Soils Matter, Get the Scoop!·

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