what causes thatch?

Discussion in 'Lawn Mowing' started by bobbygedd, Sep 20, 2001.

  1. jrodgers

    jrodgers LawnSite Member
    Messages: 229

    I have heard that the clippings actually reduce the thatch a little by their microbial action when breaking down.
  2. Runner

    Runner LawnSite Fanatic
    Messages: 13,497

    I'm sorry, I didn't mean to connote that all thatch was all clippings. Much of it is just dead material (or for all practical purposes, dead) that accumulates on the subsurface. Excess clipping are certainly a contributor to thatch buildup though. This is NOT a myth or fallacy. Also, many times, excess clippings ARE the oly thatch problem a lawn has. I know we have ALL gone into or seen a lawn that had this problem from cut grass just laying on it, and then being rained down into it. Thanks for the added info though.:)
  3. jnjnlc

    jnjnlc LawnSite Member
    Messages: 231

    Excellent Post

    I have also checked my customers and none need to be de-thatched.

    I pulled out my tow behind de-thatcher this year only to get up some bermuda grass I had killed. Worked great for that.
  4. kutnkru

    kutnkru LawnSite Silver Member
    Messages: 2,662

    This is some verbage from our Agreements explaining our Power Raking service: A thin layer of thatch can be beneficial, as it helps retain moisture and adds resilience to the turf.

    Thanks for clarifying that!
  5. GroundKprs

    GroundKprs LawnSite Bronze Member
    Messages: 1,969

    Go to a university turf website, like http://www.agry.purdue.edu/turf/pubs/ay8.htm , and you will find that thatch is basically from overactivity in grass growth - dead, tightly packed root and stem tissue (slow decaying lignin, to be exact). Live roots and stems exist also in the thatch layer.

    What is thatch? To see thatch, you will have to cut a profile out of the lawn. Simple probes usually will not give an accurate view of the thatch; use a decent sized plug, like you would get with a cup cutter. Real thatch is a dark brown layer, almost the consistency of a heavy woolen blanket. If you are calling the fluff that spring dethatchers or flail powerrakes pull up thatch, you are wrong. Scratching the surface with these machines will not remove thatch. To remove thatch, you must use a true powerrake, with fixed knife blades, or a sod cutter.

    Thatch can be controlled by core aeration. Thatch will decompose over time, but needs the soil microbe activity for this decomposition. Unfortunately, these microbes don't walk, even 1/2". So by aeration you deposit soil, with the microbes, on the surface, then it is washed down and trapped in the thatch layer. But you need a lot of aeration to correct a heavy thatch problem. For example, I once corrected a 1-3/4" thatch problem by aerating twice a year, four passes each time, for four years. The decay loosened the thatch enough that we could maintain a healthy lawn on the site again. But 6 years later you could still see the original thatch layer, not as the tightly packed original, but a slowly decomposing interface.

    Another problem with thatch is that is has a high cec, so fertilizers are easily bound in the thatch layer. This causes root growth just in the thatch layer, leading to a weak lawn and an ever thicker thatch layer.
  6. awm

    awm LawnSite Gold Member
    Messages: 3,354

    well im gon call it dead matted hay from now on then.
    in any case the soil benefits from a little airing out now an then.:)
  7. bobbygedd

    bobbygedd LawnSite Fanatic
    from NJ
    Messages: 10,178

    excelent replies folks, thank u so much, very helpful.
  8. summitgroundskeeping

    summitgroundskeeping LawnSite Senior Member
    Messages: 410

  9. morturf

    morturf LawnSite Senior Member
    from midwest
    Messages: 476

    after all the discussions, i can't believe nobody mentioned verti-cutting. Aeration is a great way to help control the thatch layer, Verti-cutting is a very aggresive method of doing the same thing. My personal opinion of "thatching" is that it is a joke. Sorry guys just my opinion.
    I was wondering if any of the golfcourse guys could chip in on this. There are few finished turf areas that are as cared for as a fairway on a golf course. These are fertilized and mowed on tight schedules. When is the last time you ever saw a golf course catch the clippings when it was mowing fairways or roughs. When was the last time you saw a golf course "power rake" or "thatch" those areas. Yes, golf courses aerate. They also verti-cut. Never seen one "thatch".
    If you think you are pulling out a lot of crud when you "thatch" or power rake, you aint seen nothing compared to verti-cutting. At least twice the amount and usually more.
  10. kutnkru

    kutnkru LawnSite Silver Member
    Messages: 2,662

    Is this not the same thing as a power rake??? I have always referred to a p-r as having a "slicing reel" and a dethatcher as having a "flail" reel.

    I wont use a thatcher/dethatcher on a property with those flail blades beating the ground. I use a power rake where the reel slices thru the first few layers stimulating growth and enhanceing fert and waters ability to be reached by the root zone.


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