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Soil, Compost & Mulch

compost, wood chips, and lignin

12 years ago

I have clay soil. It's good stuff but when I mix compost into the surface of the soil, the compost soon vanishes. The soil is improved - better texture, and the color of the soil changes, which I take to be a sign that the humic and fulvic acids from the breakdown of the compost were absorbed by the clay.

So far, so good, but I'd like to see some organic material remain because I think that would be beneficial to the biota of the soil.

I have heard of tilling ramial mulch into soil and heard the good reports of that practice. Wood chips contain lignin, which breaks down more slowly than other forms of organic matter. In the past I have sometimes included wood chips in my home-made compost, based only on whether I have any chipped wood at the time. But I'm thinking that I ought to make it a 'standard practice' so that I am repeatedly supplying a source of lignin to my soil.

(I own a beefy little Mackissic Merry Mac 12hp hammermill chipper/shredder that produces a chip size controlled by the size of the screen. Also, the chipper feeds the chipped wood into the hammermill, so the chips get chipped [ul]and[/ul] shredded.)

Yes, I'm aware that a strictly wood-chip compost will inhibit plant growth, but I'm thinking that if the woody content of the compost was a minority component, (20% max.), I would be able to avoid the issue of unfinished compost.

Your thought?

Paul

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Comments (4)

barnhardt9999
12 years ago
I too have clay soil. In my compost this year I had a lot of small twigs (maybe 10 -15%) that weren't fully composted and I just went ahead and mixed them into my soil. I noticed the plants were growing a little slower than normal so I gave them a little high nitrogen fertilizer and everything got back on track quickly. I'd say it's ok to add uncomposted wood chips; just have a little fertilizer on stand-by in case you notice slower growth from nitrogen getting bound by the wood decomposing.
Kimmsr
12 years ago
The compost that you add to your clay does not disappear but is digested by the Soil Food Web who use it to feed the plants you grow and to change your soils structure, as you have seen.
Tilling materials into the soil that are high in carbon can cause the Soil Food Web to spend large amounts of energy, using available Nitrogen to the deteriment of growing plants, to quickly digest that material. However, if that same material was to be layed on the soil, as a mulch, the carbon would be added to your soil slowly by the same Soil Food Web and would not have an adverse affect on available Nitrogen.
This video, about an hour and a half long, might be of some interest to you.

Here is a link that might be useful: Back to Eden video
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Finally stopped raining long enough to process a batch and get some pics. In the picture below, the 1st pile (oldest) is on the right. Dumped against it on the left is the newer load. Inside the pile... The chips are raked down into the 'staging area' where they're spread out to dry enough for sifting... I use the lid off a garbage can as a 'catch' and frame for the hardware cloth... First, the chips are 'rubbed' through the mesh to clean off the good stuff, and to leave behind only the larger chips. The finer chips, and the compost is pushed through... The Clean chips... The finished batch after the first screening... The compost is then lightly shaken back through the screen twice to separate out most of the 'fines'... I could get a thinner screen to remove even the tiniest wood material, but I see no reason, nor any adverse affects. The finished compost... From this batch (an average), I got about 12 gal. of coarse chips; 3 gal. of fines; and 9 gal. of finished compost. I'm saving some of the fines to make an experimental potting mix for transplants. The rest of the fines are tossed on to the newest pile to break down further. The compost is used as... well compost lol. And, the chips are spread as mulch over perennial beds, and on garden paths...
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toxcrusadr
12 years ago
After adding organic matter to my clay for 20 years, I have become an advocate of *also* adding some silt or silty sand when I can find some, to subtly adjust the particle size distribution. Not in place of organic matter, but in addition. One has to be careful adding sand to clay, and there are numerous threads on this topic already.

I also find that mulching with compost ingredients, half done compost, wood chips etc. will keep the soil moist and reduce the compaction resulting from alternately drying out and being hammered with rain.

I haven't tried what you suggest and I too would be concerned about N depletion.
oliveoyl3
12 years ago
I have rocky clay - pit run type soil in most places as the topsoil was all removed prior to us living here, so compost is the only way we can garden. It gets better over time. We started a small plot & made it bigger as we went.

Wood chips are useful in their own piles to break down, pathway material or surface mulch, but not tilled in to the soil. You're right it does disappear and it's a lot of work to haul it. Nice that you have a chipper so you can put the chips where you want them.

all organic matter breaks down
some is active & inactive organic matter
continue to add compost to soil & mulch

A good resource is the book below for explaining the methods of composting & science behind it. Easy to read and very complete.

Here is a link that might be useful: compost gardener book

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