Products to loosen clay soils

Discussion in 'Landscape Architecture and Design' started by Coffeecraver, Nov 9, 2004.

  1. Coffeecraver

    Coffeecraver LawnSite Senior Member
    from VA.
    Posts: 793

    Products to loosen clay soils
    Gypsum, soil penetrants, and sand are often recommended–each for a different reason.

    Clay soil absorbs water slowly because the clay particles are tiny. They interlock tightly, with small air spaces, so water can only penetrate as quickly as it can fill those spaces. Compaction of the surface by foot traffic, rainfall, or overhead sprinkling smashes these particles even closer together. If you try to put water on faster than it can penetrate the excess will puddle or run off. Loosening clay soils usually involves breaking the crusted, compacted surface, or amending the soil with products that increase the air spaces. Clay has high cation-exchange capacity, meaning that it readily holds on to and exchanges positive ions.

    Gypsum is calcium sulfate, usually sold in powder or granular form. It is a chemical buffer, meaning that it tends to cause the soil pH to move towards neutral from acid or alkaline (we recommend sulfur in this area instead). Advocates say that it "penetrates clay particles and loosens the soil structure," presumably by means of interaction of the calcium and sulfur ions with the clay particles. They caution that it works slowly, requiring annual applications over at least three years.

    Soil penetrants are said to work much like detergent, breaking the surface tension, which might slow down water. "Ethoxylated fatty alcohol" is an additive to the Vitamin B product mentioned above. It is hard to imagine that a material sprayed on the surface would make much difference this way.

    Neither gypsum nor soil penetrants will have as much effect (if any) on clay as will amending it with larger particles that increase the air spaces. Adding sand is NOT helpful. Although sand particles are larger than clay, they are still just little rocks. In fact, the clay and sand particles interlock to form a structure similar to concrete! But mixing in large amounts of organic material will make a big difference. Composted leaves or manure, or shavings (not fresh), or even fine bark all add air spaces. Even spread out on the surface, these will filter in to the soil by means of weather or worms, continuing to naturally amend the soil as they break down. Organic materials improve the soil’s ability to store and release water and nutrients as well as enhancing penetration.

    Compaction of the surface of your lawn’s soil frequently leads to runoff. Here you can break the surface of the soil with a mechanical aerator, and then rake in organic material. In small areas the aeration can be done with a step-on device, while machines for larger lawns can be rented locally. It’s important that the device pulls a plug of soil out, rather than just punching a hole. The popular notion of "aerating" with golf shoes is not effective.

  2. Rtom45

    Rtom45 LawnSite Senior Member
    Posts: 456

    Also see the pesticide and fertilizer heading below, there's a great thread on the pros and cons of gypsum.
  3. blafleur

    blafleur LawnSite Member
    Posts: 229

    A product new to this area is expanded shale. It is touted to be the latest greatest (yeah, I've heard that a couple times) miracle worker for heavy clay. It comes alone or mixed with compost. I tried some recently and will monitor how it does. It looks like gravel and is lightweight from the heating process used which, as I understand it, pops it like popcorn.

    It has no nutritional value so is supposed to be mixed in with an organic amendment. Anyone else had any knowledge and/or use of this.

    I had heard gypsum was not a good idea for alkaline soils, but cant remember why.

  4. activelandscaping

    activelandscaping LawnSite Member
    Posts: 241

    I use a mix of crumb rubber, rice hull's and course organics. My preferred method is to first verti-drain the area, then drag the mix into the holes. It's amazing what a difference it makes.

  5. AGLA

    AGLA LawnSite Bronze Member
    Posts: 1,742

    Gypsum is bad for alkaline soil because it is a lime (no, not the same as limestone). In other words it makes the soil more alkaline.
  6. D Felix

    D Felix LawnSite Bronze Member
    Posts: 1,898

    The only shale I've had to deal with in recent memory is on the project we are currently working on.... From dealing with it, I can see how heating it would cause it to pop. Our shale is mostly sandstone, and trust me, it doesn't do ANYTHING for the drainage there! But it's also embedded, not an amendment.:)

    Depending on particle size of the expanded shale (again, I haven't seen what you are talking about), I could see it being just like sand and actually decreasing soil porosity. You'd need to add a lot to make it do anything....

  7. Grassmechanic

    Grassmechanic LawnSite Silver Member
    Posts: 2,697

    Sorry AGLA, but gypsum has NO effect on soil acidity. It wil not change the ph of soil at all.
  8. blafleur

    blafleur LawnSite Member
    Posts: 229

    The size of the expanded shale is about 3/8". It looks like gray pea gravel, but picking it up, it is much lighter than any gravel. It is being pushed awfully hard in this area for a new product, I am always skeptical of these claims, because they are rarely by people who wont profit from it. I used it at a residence last month where the customer agreed to let me use it as a testing ground for many things, including flagstone running through the driveway(as per an earlier thread), and this shale. I'll be checking its effectivness. My main concerns are its effects, if any, on plant health, and long term effectiveness at keeping the soil loose.

    I used about 3" shale with about 4" compost. The soil is really loose now, but it would be that way with just the compost now, but with only organic matter, by next year it would be back to sticky clay. I always let customers know this, and the importance of keeping mulch on the beds, but most dont.

    The best thing I have seen for long term soil friability is attracting and keeping worms. I have one customer that I did the original installation 4 years ago and the bed maintenance season change out since. I used plenty of compost then, and have added a little more with each seasons change out, along with mulching. The year after original installation, the soil was appearing to return to tight clay as the compost began to break down, then the worms started showing up. Now her beds are full of worms, and the soil is like potting soil. Annuals have correspondingly improved as worms have increased. They use no pesticides in the beds, and I use organic fertilizers.

    Here is a site with some info on the expanded shale, it seems to be mainly in the Texas area now.
  9. AGLA

    AGLA LawnSite Bronze Member
    Posts: 1,742

    Gypsum does act as a lime in sodic soils. The sulfur gets ripped off and frees up the calcium. If I remember correctly. Maybe someone in alkaline soil land will back me up on that. Sodic soils are high in sodium which occur in many of the same prts of the country alkaline soil occurs.
  10. activelandscaping

    activelandscaping LawnSite Member
    Posts: 241

    While Gypsum does not appear to increase or decrease Ph levels, appearently it can raise salt levels in poorly drained soils, like clay.

    Here are a couple of good links that have the characteristics of gypsum. It does not appear, from the data I have seen, to provide any type of practical solution. The data that indicates it can reduce sodium levels requires site treatments that are not realistic. As for it's purpose I havn't been able to discern any which is practical........... but I should note that I have no personal experience with this product.

    1)Gypsum Magic
    2)The Value of Gypsum


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