Here Craig is sifting finished compost (beautiful humus) from Bin 3 (the black cylinder) into the wheelbarrow  for spreading on the beds in early spring. Behind him is a huge pile of dry leaves for layering between green and organic matter all season. In the top photo the far right bin is the newest pile. In the middle bin is half-composted stuff from Bin 1

The three-bin compost system starts with three containers. 3 feet cubic is the smallest they can be for there to be enough depth to allow it to heat up. We have two cubicles, one wonderful huge ventilated plastic cylinder with a lid, a space behind them for a huge pile of leaves, and a wheelbarrow with a coarse screen to sift the finished compost.

The idea is to maximize the heat-producing chemical reactions to speed the transformation of carbon-rich veggie matter into nitrogen-rich humus. The three bins are so you can get three full batches of humus in one season.

In the first bin you alternate layers:
6 inches of leaves or other stuff from the “crunchy” (carbon)list; a sprinkling, barely covering, of “green stuff” (nitrogen – this is what starts the “fire”. Layers of living organic matter (we use damp leaf mold, swamp goo, or it can be wet kitchen compost, or well-composted manure) really gets it cooking. Repeat these three layers as often as you can gather the stuff until #1 is full.

2 weeks after Bin # 1 is full (this time depends on a lot of factors) or when it seems to have gone down by half or more:
Take the top layer of Bin #1 and put it on the bottom of Bin #2. Continue until Bin #1 is empty. Start Bin # 1 anew.

After 1 week more (again, this depends on how well it's been cooking) or when it no longer looks like the stuff you put in:
Move the stuff from Bin #2 to Bin #3. Sift Bin #3 and use in your garden, mulching where the plants are growing the most vigorously (using up the most nutrients from the soil)

There should be time to do this three times over the summer.

Keep it damp if it doesn't rain for awhile.

You don’t need worms in this system. But we saw the worms in their donor's Bin # 3 and it was a beautiful thing. Don't need manure here, either. Use it in the windrows if you have a source. If you want to super-charge it, spike it with your pee. See my page on fertilizing with urine.

My friend Mike is quite scientific about composting. I made a special page here.

Hi Lynn, excellent results.  There are several stages in the 'heating up' periods in which different bacteria, enzymes and other microscopic critters flourish and consume.
 
Your layering sounds perfect- each layer just covering up the previous one.   A  layer of leaves might be 2 or 3 inches thick compared to only 1 inch of grass clippings, or 1/2 inch of dirt, for instance. 
 
We didn't talk too much about moisture, but you're right in thinking that is a major component.  Too much moisture and the air gets forced out- an 'anaerobic' environment.  Too little moisture and the critters go dormant.  The right amount of moisture is the same as if you took a wet rag and squeezed as much of the water in it out.  (Maybe you'd twist it and squish the water out).  The just-squeezed rag is the same moisture content as you'd like your compost pile to be.
 
Gary once once asked me why his black plastic barrel he used for compost didn't seem to be producing any compost.  When I checked it turned out that over the months the rain and accumulated kitchen wastes had produced a sodden soil-soup that would only develop moulds and fungus and bad smelling critters with very little composting going on. Maybe there was too little drainage, maybe he was composting buckets of bath water or something, but too much moisture displaces the oxygen and the resulting activity is slow, cold and smelly.
 
In most compost bins, water seldom if ever builds up to the 'sloppy' stage, except maybe during the melt of early spring. Having a bin that is too dry can be easy to do, and once fully built it can be difficult to moisten the middle.  Some compost items such as leaves or sawdust can be very dry.  Moistening each dry layer might be the best way, but I only add water when the days are hot and dry and I suspect the pile has become the same. At those times I throw in a bucket of water or hose it down.  In the end, the middle of your pile should be about the same as a wrung-out rag. 
 
    The heating might go on for several days.  When the pile gets cold again, turn it over with layers of green in between and it'll heat again.  Each 'heating' can shrink your compost pile by up to 1/3. Each turning concentrates the pile and 'uses up' the carbon.  What we're really doing is converting plant food to a more digestible form, like mushing up carrots to feed a baby. In order for the plant to 'eat' the leaves and grass clippings, both have to be broken down.  A compost pile 'pre-chews' the carbon and nitrogen into a substance that can be more readily taken up by the plant.
 
I figure the main thing I want to do each year is get compost back onto my garden. The very minimum amount would have to exceed everything that I was taking off that ground.  So if it was potatoes, I would estimate how much all those potatoes, stems and tops, as well as all the weeds I pulled out, weighed. I would have to put at least that amount of compost back on that bed in order to replace what I had extracted as well as add to the soil every year.
 
    That being said, I get the compost on the bed any time that I can.  If it's early spring, I can maybe spread it over the bed and fork it in.  If at planting time, I can mix the compost into each hole.  If the plants are already established, I'll just top-dress or mulch with compost.  They say the worms will eventually take the good stuff down.  In the meantime a layer of compost keeps moisture in, keeps weeds down, and ensures that bed will be well fed.
  
Compost cannot burn or hurt a plant.  I suppose that eventually we will all garden in plots that may be 'full of compost'.  That is what we'll aim for.  Just one reminder that unfinished compost has a lot of stuff in it that is not black and crumbly, and can be identified as twigs or stems or leaves or whatever.  These are likely to be carbon sources, and it is better to re-pile that stuff layered with greens and let it heat up again. The ground cannot compost stuff as well as you can, and un-composted stuff 'steals' nutrients from your soil.
 
    When you have stalks or leaves or husks or whatever in the soil, the earth sets about to break these carbon sources down into plant food.  To do that there has to be nitrogen added to the carbon, in the presence of moisture and oxygen, and there we are back at composting again.  The trouble is that the earth takes its precious nitrogen and instead of allowing the plants to sip at it and grow big green leaves, the nitrogen becomes 'bound' to the job of breaking down the carbon before the plants can get a taste of it.
 
Adding carbon directly to the soil may result in a nitrogen deficiency for the next season or two.(Eventually, adding any organic substance to your soil is good, in the long run. ) Use carbon stuffs in the compost in layers with green stuff, frequent turnings and adequate moisture and drainage. Add compost to the soil- ideally aim for adding twice the amount of whatever comes off or out of the soil with compost at any time you can manage throughout the season.
 
I'm running out of leaves, and without them my composting efforts slow.  I have a pile of saw-dust, and that is very high in carbon so just a sprinkling on a layer of fresh-pulled grasses is a good mix. Besides weeding I just go wherever the lushest grasses are and start pulling. I've got one pile cooking, ready to turn again with a little layer of greens between each layer of compost. I'll keep repeating this process every couple of weeks or so until the stuff is what I want. If a pile becomes cool, you might as well start gathering green grasses and re-piling it.  It will then heat up again and shrink down, turning all that stuff into soil. I have some 'screens' as well that allow you to sift out the unfinished strands and chunks as the black and crumbly fall into the wheel barrow.  Good for house plants and planters.  Unnecessary in most cases.
 
 
The other things I've been experimenting with adding are mixtures that have lime, bonemeal and bloodmeal in them.  


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