Clay Platelets

Discussion in 'Turf Renovation' started by Smallaxe, Jan 12, 2013.

  1. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    The biggest problem with irrigation on soil health, is usually the problems with clay platelets...
    Here is the best little introduction to Soil Structure I've ever come across...
    Short, simple and yet very insightful...
    "... Air, water and plant roots can penetrate deeper in the soil; this can be important to plant survival during times of drought. The larger voids serve as short-term storage space for water, easily accessed by plants.

    ... Aggregation begins with flocculation of clay particles (platelets) into microscopic clumps called floccules; the cations that are caught between two platelets attract the negative charges on both platelets, binding them together.

    ... The polyvalent cations (including Ca2+, Fe3+ and Al3+) may also attract and bind with hydrophobic (water repelling) humus molecules allowing them to bind to clay surfaces. These clay-humus particles bind with each other and with grains of silt to form the smallest of the primary aggregates, perhaps as small as 0.01 mm. ...

    Notice what they say here about the heaving/shrinking, wetting/drying and freeze/thaw...
    "... As a soil dries out, the clay platelets move closer together and cause shrinking in soil volume. Cracks will form along tiny zones of weakness, and over the course of several wet/dry cycles this network of cracks becomes better defined. Plant roots, as they repeatedly remove water from the same vicinity, reinforce a drying pattern and contribute to physical aggregation of the soil. The process of freezing and thawing in the soil also contributes to the drying process as ice crystals form. And shrinking and swelling that results from wet-dry and freeze-thaw cycles creates tiny cracks or fissures (shrinking) and pressure (swelling) that break apart structureless masses of clay to eventually form soil peds or aggregates."
  2. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    This article also covers,,, Human Activity,,, and its sometimes positive and sometimes negative impact on soils:

    "... Additions of fertilizer to agricultural land can have a positive effect on soil structure. By increasing plant growth and quality, roots help with stability of soil aggregates. Applications of liming material (high in calcium, a key player in flocculation) encourage better structure and tilth. Organic materials in the form of plant residue or animal manure quickly decompose and participate in the development of soil aggregates, and also provide favorable conditions for microorganisms. ...

    "... Conservation tillage practices have greater benefits to the soil than conventional tillage. Under conservation practices, the need for tillage is minimized and plant residues are left on or near the soil surface. Conventional tillage requires more frequent tilling. A primary pass is made to turn plant residue several inches below the surface. This is followed by secondary tillage operations such as harrowing, which kills weeds and breaks up clods prior to planting. After planting, the soil may again be tilled for weed control and to break up any crusting of the surface soil. These multiple passes can compact the soil and result in the formation of a “plow pan” and platy structure. The amount and size of pores will decrease in this zone with concomitant air and water movement. With decreased rates of infiltration, surface runoff and soil erosion become issues. Plant roots have greater difficulty penetrating the platy structure and compacted soil, and limited rooting depth can affect plant survival. ...

    An important point of destruction of soil structure is understanding the last sentence in the paragraph:

    "... Irrigation, if not properly applied, can compound this problem by breaking up aggregates, increasing sodium content, and leaching clay. "
  3. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    "... Many types or shapes of structure occur in soils. Other soils have no true structure and are called structureless. Certain deposits, for example sands in a sand dune, are called single grain because there is little to no attraction between sand grains. On the other textural extreme, some clay soils occur as large cohesive masses and are termed massive in structure. Many soils, however, will exhibit definite and repeatable shapes that we can describe with four general categories."
  4. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    Based on the idea of excellent lawn care, or bedcare for that matter,,, I expect there is a way of doing things better than the way it is being done now...
    I find Strong Granular Structures under mulch in the flower beds and I find moderate granular structures in a moist but not over watered lawn when I look under the lawn debris...
    I find Platy structures of bare dirt lawns that recieve irrigation that appears to be in excess...
    My point to all of this is to help LCOs, interestted in excellent lawns to achieve the excellent soil necessaryto get there...

    Enjoy... :)
    "... Grade describes the distinctness of the structure, and is combined with the cohesion of the soil within units compared to the adhesion between individual units. Terms that are used for grade are weak, moderate and strong.

    If the structural grade is weak, aggregates are barely observable in the soil profile.

    With moderate grade the structural units are well formed and easily distinguished in the soil profile. When disturbed, the aggregates part into a mixture of mostly whole units, some broken units, and some material that is not in structural units. Individual peds will part from adjoining peds somewhat cleanly.

    When grade is described as strong the structural units are clearly seen in the profile and shape is easily identified. Peds separate cleanly from other peds and retain their shape when disturbed by shaking. ..."
  5. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    "Soil structure is the second most influential characteristic, after texture, in determining the behavior or any given soil. Soils with similar characteristics (vegetation, climate, texture, and depth) but different structure will react differently under similar conditions. Structure influences water infiltration, building site development and growth of plants. When combined with soil texture, structure influences the distribution of soil solids and pore space (called the soil bulk density). ..."

    Vegetation, climate, texture, and depth may all be things that are equal,,, but becuz the "Structure" is different, that makes EVERYTHING different...

    Funny how that is NOT important on a Professional Lawn/Landscaping Forum... We can't understand why we have some of the problems we have for that very reason... we can't discuss microbials or soil health, intelligently for that very reason... One thing we do very well however, is condescend to someone we don't like and express how dismayed we are that he/she is so unable to understand... or just call them ignorant... :)

    I'm not talking down to anyone,,, just curious if soil structure matters to anyone one this forum...
    WHY? ...or... WHY NOT???
  6. phasthound

    phasthound LawnSite Fanatic
    Messages: 5,160

  7. Skipster

    Skipster LawnSite Bronze Member
    Messages: 1,086

    How do you propose managing soil microbiology populations? Your link doesn't provide any insight that is different from what we've discussed previously. SmallAxe might say, "Now that we know the WHY, we need to know HOW to manage these populations.

    Your link backs up the uniersity links we've looked at before -- it tells us that microbes are their most active in healthy and robust plant systems. This link supports the conventional management view over the "feed the microbes" view.
  8. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,807

    Good point, Skip.
    If someone intended to feed the microbes...would he then spread sugar on the soil? Would the soil structure then be improved?

    Is anybody willing l to try a test in indoor flower pots? Clay soil loose, clay soil purposely hard-packed, and clay soil hard-packed with sugar added--what is the difference in seed germination if buried at 1/4 inch?
  9. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    If you have a basic mineral clay, w/out a decent amount of undigested OM, you are likely to just get a mold growing on top of the clay from your sugar app...

    If it were me, I would put a layer of dead grass in the pot,,, even worked into the surface a bit to have something of substance for the microbes to begin building structure with the clay platelets...
    The clay pots will compact themselves with a good soaking with water... So I would make the difference between these various pots the frequncy and types of watering... i.e. one can be kept wet , the 2nd canbe allowed to dry completely between waterings and the 3rd could be overwatered...

    For number 2,,, I wouldn't let the entire pot dry out between waterings, but would make sure the top inch or so, is completely dried...

    I believe that number 2 is the critical formula for building decent soil structure... :)
  10. Skipster

    Skipster LawnSite Bronze Member
    Messages: 1,086


    Once you dig up soil and put it in a pot, you have disturbed it and changed its structure from what it was in the undisturbed ground -- so, it wouldn't at all be an accurate representation of field conditions. Universities would test this in situ using lysimeters pounded into the ground.

    If we think that microbes alone are responsible for building structure, then we don't understand microbes or even soil structure very well. You've also shown us that you don't understand clay very well. 2:1 clays shrink and swell with wetting and drying -- which causes cracks and promotes structure.

    But, it seems like you're looking at minutia to try to find some magic bullet to grow grass. Soil structure isn't that important to growing a lawn, unless th esoil is a structureless solid mass. As we discussed before, microbial ativity isn't the magic bullet to growing grass. Growing grass creates healthy microbial populations, not the other way around.

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