Does Compost Fade Away?

Discussion in 'Organic Lawn Care' started by GeoPappas, Feb 15, 2005.

  1. GeoPappas

    GeoPappas LawnSite Member
    Messages: 7

    Some background: I live in the Raleigh/Durham area of NC. We have thick clay soil and tall fescue. It seems that the builders just laid sod on top of the clay soil, so the only "topsoil" is that which came with the sod (only an inch or so). Since the topsoil is so thin and the clay is too thick for the grass roots to go into, the grass doesn't grow very well and needs to be overseeded constantly.

    Many people suggest that if you have thick clay soil (which I do), adding compost as a topdressing to it once or twice a year will eventually build the soil up over time (giving the grass roots more room to grow).

    But in "Sticky: FAQ #2 - How are they used (pt 1)", there is a statement:

    "Compost is a material that will be completely digested in a year or two leaving no depth to it. So 4 inches will become zero inches. This is an important concept."

    This seems to go against what I have read elsewhere. So which statement is correct?

    Does the compost build up the soil over time?

    Or does it fade away into the sunset?
  2. YardPro

    YardPro LawnSite Gold Member
    Messages: 3,570

    microbes break down parts of the compost. the rate of decomposition depends on the material and the size (surface area) of the pieces. it will never become zero becuase all the material will not be decomposed... now it will get very close to zero, but there will still be a layer, however thin.

    topdressing works OK, but to improve the soil it will take many years to build up a layer that will make any difference.

    you may be better off having your property renovated. i would consult a LOCAL professional like bland landscapes, etc...
  3. dishboy

    dishboy LawnSite Fanatic
    from zone 6
    Messages: 6,161

    I do not know about fading away, but I am sure my mower has enough vacuum to suck it up when not mulching.

    For this reason [among others] I mulch after a compost application or Organic fertilization.
  4. Lawn Sharks

    Lawn Sharks LawnSite Senior Member
    Messages: 394

    It will fade away to almost nothing but it does help. You may want to consider gypsum or lime program to try and get the clay looser and aerate and top dress with compost twice a year, compost and sand in combo may help.

    Good luck.
  5. Dchall_San_Antonio

    Dchall_San_Antonio LawnSite Senior Member
    Messages: 327

    The bulk material in compost is an organic food for microbes. Good compost will be full of the microbes that digest the bulky material and thus will completely decompose the bulk material eventually. How fast that happens depends on temperature and moisture.

    There is more to compost than lending temporary depth to a soil. The main purpose of compost is to deliver those microbes to your soil. Excellent compost is full of beneficial microbes needed to give structure to your clay soil. What you should be driving for is to loosen the clay by developing a healthy population of microbes, especially fungi but not to detract from the bacteria. If you apply compost and follow up with repeated applications of good protein sources (and water), your microbes will multiply and thrive. Once you have them thriving, they will surround the clay particles in your heavy clay with a slimey goo that does several things. One is it tends to hold moisture longer than dry minerals do. Second is that the goo holds the clay mineral particles a little farther apart than if they were all aligned perfectly. When you get clay particles glued together with organic slime byproducts of the bacteria, that is called soil crumb structure. Then along comes the soil fungi to push these soil crumbs apart. Fungi develop with their own sort of a root like structure. They send out "arms," called hyphae, deep into the soil. These structures are searching for minerals and organic materials in the soil. When they find them, they latch on and absorb them by any of several means. When these fungal hyphae get wet, they swell up and push the soil crumbs apart. When the fungal hyphae dry out, they shrink back away from the crumbs and allow air to penetrate where it wasn't penetrating before. Then when it rains, the water can flow down in these air gaps to depths that it could not flow before.

    Thus the ability of the soil to absorb water is dependent on the health of the microbes in the soil. When they are there (not killed off by chemical poisons) and well fed (protein and carbohydrates), they will work for you to soften your soil and feed your plants. Compost is the best way to get them there. Then what ever happens to the bulk material in the compost is immaterial. What I care about is the quantity and health of the living microbes.
  6. Lawn Sharks

    Lawn Sharks LawnSite Senior Member
    Messages: 394

    Very well put! A key part is "follow up with repeated applications of good protein sources". It doesn't just take compost. Compost adds microbes and It takes well fed microbes to realize the full benefit applying compost to the soil. If you kill em you really aren't getting what you want from the work it took to topdress.
  7. Do not remove clipping, they add organic matter, fert, and water!

    When you get the soil chemistry right, in other words, the proper base saturations of ca, mg, k, h, (these 4 will total 95%) and micro nutrients, your clay soil will be looser!
  8. NAT

    NAT LawnSite Member
    from Zone 7
    Messages: 96

  9. Neal Wolbert

    Neal Wolbert LawnSite Senior Member
    Messages: 407

    DCHALL, Assume you are referring to endo-mycorrhizae when you mention soil fungus/hyphae? Just what "chemical poisons" are you referring to? Neal

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