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| On another gardening forum I was asking about using my bountiful stash of composted horse manure several inches deep when establishing my new gardens not only to improve the soil but also to raise the beds to level of the walkways. I was warned that the compost will disappear over time so the "lift" to walkway level was only temporary. Hmmm. Ok.
Which begs the question: where exactly does the compost go since in our physical world nothing actually disappears? |
Follow-Up Postings:
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| My guess would be that it gets absorbed into the soil. Compost is kind of fluffy as it is, so I imagine that things like rain erosion, soil absorption and use by plants and microbes would in fact break it down. The compost isn't likely to just "disappear". Remember that it is organic matter. People also eat organic matter. What we doesn't just "disappear" either, the um, matter isn't returned directly to the earth as the same mass that we consumed. Much of it does get used up. It doesn't just "disappear", but it does go through breakdowns and chemical changes through our digestive system and bodies, and is converted to energy, which is used, and then expelled in many different forms (gases, solid waste, etc.) I imagine the same thing happens to compost in a garden/soil ecosystem. |
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| I agree with tomfromKS. It would be great if the compost could be applied once & we could grow fruit & vegetable 5-10 years, WITHOUT adding more compost. Most of it goes into making better soil & is not lost. |
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| It doesn't disappear, but it does continue to break down. Eventually, it will end up as humic acid and take up about 10% (or so, depending on the original compost) of the original volume. |
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| As bpgreen stated compost, and other forms of organic matter, do not "disappear" but are converted in plant nutrients. Some, mostly the less easily digested bits, becomes the humus in your soil while the Soil Food Web uses the rest to feed themselves and your plants. Ma Nature created a great aray of wee thingys to work in soil and convert what most people think of as waste to be gotten rid of into something the new plants can use to grow on. Nothing disappears, everything is transformed into something else. All soils need organic matter added routinely because that is the only part of the soil makeup that is digestable and useable to feed the plants that are growing there. Where do the nutrients that feed our vast forests come from? Certainly not from the synthetic, non renewable, sources used for much of the commercial fertilzers used today (not very readily available until after WWII) that are causing a great deal of pollution in our world. |
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| C6H12O6 + O2 --> CO2 + H2O + energy The chemical bond energy of glucose is released as ATP and heat. ATP is chemical energy and is used the soil micro organisms. Since the breakdown of glucose is not very efficient, more than half of the energy released is given off as heat. This is the heat that you find in a compost pile and also the heat that keeps humans warm and toasty. This breakdown is the reverse of photosynthesis. So yes, the organic material disappears. Some of the byproducts are used by plants. If you remove all the plant material, then the soil is depleted of that organic material. So adding a bit of compost every year maintains the balance. |
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| subk3, I'm no chemist but know what you're saying. Every second year I apply a 3" layer of finished compost to the garden and till it in. I've been trying to increase the soil level in my veggie garden, which is happening slowly, but probably because I layer in shaved sod to my compost piles and the clay doesn't go away, just adds to the mix. The OM just breaks down and adds to the nutrient level. The soil level in my garden hasn't changed much in over 15 years with all this effort. So, why do I keep doing it? I never use fertilizer and EVERYTHING grows like a weed. Who cares where the OM goes unless it is into the size of the veggies! By the way, I topdress 1" annually around the perennials and they do the same. Compost rocks. hortster |
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- Posted by californian 10 (My Page) on Sun, Apr 24, 11 at 13:11
| Compost does disappear in my clay soil garden. In each of the three previous years I spread a 10 cubic yard dumptruck load of horse manure/wood shavings compost over my garden, for a total of 30 cubic yards, plus extra bagged mulch and steer manure. When I was digging holes to plant my tomatoes this year there is no sign of it, the soil is back to pure gray colored clay. But it must have done some good because it gets easier and easier to rototill my garden every year. There are earthworms in the soil because I usually uncover at least one while digging a hole to plant something. From what I read the microbes in the soil gradually eat it all up. |
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| I understand that some small (perhaps very small?) percentage of organic matter is long-lasting, and that this is what is properly called "humus." So, it might be possible to raise the level of soil a little bit, over a long period. |
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- Posted by vermontkingdom 4a (My Page) on Mon, Apr 25, 11 at 7:05
| The soil level does indeed raise over time. We live in a development and have been gardening at this site for 40 years. Over that span, through my compost, I've probably added more than a thousand bags of leaves/grass clippings and probably that many 5 gal containers of horse manure. (Each Sunday, in the spring and fall, after Sunday worship I visit a friend who boards horses. Still in my Sunday's finest, just substitute boots and gloves, I put 24 five gal containers of manure in my little red Neon. Needless to say, my wife doesn't allow me to use her car for these transports. I've been doing this for years.) Our garden is at least 10 inches higher than the lawn it can from four decades ago. It's rich and productive. And, if microbial soil life hadn't continued the decomposition of the compost material through their respiratory processes, it would be several feet high. Unfortunately, when my gardening days are done, and unless the next owner continues the compost regimen, the garden's height will slowly subside to the lawn level once again. |
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| Thank you all! "C6H12O6 + O2 --> CO2 + H2O + energy" I completely forgot the energy component of the equation. Fortunately for me, I have four very reliable poopers in the barn and a green tractor with a front end loader (instead of a little red Neon!) so should be able to amend 'til my hearts content. |
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