Grow Your Own Soil: Compost Crops

Readers will note that I am HUGE on living soils.  We moved into a dead, denuded landscape and have spent the past 5 years dutifully rebuilding them.  The single most important thing in healing soils is to add organic matter – essentially getting carbon back into the soil.  Why?  Carbon is the primary building block of all life and it is the fuel of the soil food web -from the zillions of bacteria and miles of fungal hyphae to the worms that feed on them.  We’ve been trucking in organic matter for years now – mostly wood chips, but also straw and manures; by the ton.  In fact, over the past five years I would estimate that we’ve surpassed 20 tons of raw material that we’ve either added directly to our soils (manures), or mulched (wood chips and straw).  That may sound like alot, but at least half of the carbon is lost to the air as part of the decomposition process (no fears for global warming as the carbon in wood chips and manure was atmospheric carbon just a year or so ago before it was sequestered by the plants), plus to add an inch to a 1/4 acre (11,000 sq ft) which is my yard (minus house and driveway)  you need to have about 9 tons of compost.  That’s 34 yards of finished compost, or over 100 cu yards of raw material.  Helping others get to this point is why I own a dump truck.

The result is that our soil is teeming with life and the gardens are really starting to “pop” this year with trees adding multiple feet of growth, 5+ cuttings of the Russian Comfrey, and sunflowers over 8′ tall.  We will continue to “uppen” our soils with compost and mulches for decades to come.  But I am trying to do this on as low of inputs as possible.  In the last 5 years we have built our garden soils up and the lawn is getting healthier every year.  It is time to try to see how sustainable I can make this system.  It is time to start growing my own soil.

To grow your own soil you need plants that pull carbon out of the atmosphere, which of course all plants do, but some do it really damn well.  I must tip my hat strongly to John Jeavons and his work on sustainable gardening here, but for annuals the choices are not too hard – what gets really damn big, with a thick stalk?  Think sunflowers, sorghum, corn, quinoa, amaranth, etc.  Add in all the small grains if left to dry out into straw and you get the idea.  Perennial crops are also money as well.  There are a wealth of BIG plants in the tall grass prairie – my favorites are cupplant, giant Joe Pye weed, sunchokes, and the myriad perennial sunflowers like maximillian and ox eye.  The true Big Guns in this area are rapid growth trees, often referred to as weeds, harvested as coppice such as willows, box elder, black locust, and even chestnut and ash.  Other “weeds” like lambsquarter, ragweed, and buttonweed get 6’+ tall , and even invasives like buckthorn coppice well.

Today I spent an hour touring the back yard with my Big Az 10 cu ft mulch wheel barrow, my sickle, and my new brush axe pulling weeds, hacking down old raspberry canes from last year, cutting back insurgent sunchokes, and taking the 4th cutting off the 60 or so russian comfrey I have around the gardens.  That produced an immense amount of green material – piling it into my utility trailer I easily had 80 cu ft.  That is far too much nitrogen for a pile so then I got out my loppers and a pruning saw and took some prunings from the buckthorn out back and two of our willow shrubs.  It wasn’t enough, but in a few years the 2 dozen box elders and  willows I have planted will be on line.  Here are the results.

about 100#'s of material, but dang is it bulky. Brush Axe is leaning on the trailer.

That is from one lap of the backyard – I can do this about 3-4 times a year at present.  In years past I just threw all the weeds into the compost bins, but it doesn’t work too well as the stalky stuff takes too long and the full size leaves mat up.  Now with the Bio-80 shredder it makes marvelous weed puree.

Entropy ala weeds. At least half that pile is/was comfrey so the compost will be awesome. The recycling bin is the chipped tree prunings - not enough to offset the greens, but its a start..

Now the Bio-80 is powered by gasoline, and I am likely to catch flak in the comments for burning dead dinosaurs to save the world.  I agree- its not ideal.  But I am building a transitional system and am not afraid to break some eggs to make an omelet.  The chipper is only 5hp and ran for about 20 minutes using less than a cup of fuel.  In future years I hope to find a way to power the chipper on methane from the ‘Midden or ethanol from a local co-op.  But for now I’m in bed with BP on this one.  One very cool option would be to use a chicken “shredder” to break down the green material – 4 layers in a confined pen would make short work of this over a week or so of adding an inch or two a day for the girls to scratch in.  Of course that is illegal here.  Working on that too…

This bin is 40" cubed and is about 66% full. This will settle almost 30% in the coming days. Making soil takes ALOT of plant material. Plant more trees!

Finally, it takes ALOT of plants to make a yard of compost.  A yard of finished compost weighs about 550#’s.  So the 100-150#’s of material that I put in, most of which was water that will evaporate out, is just a start. But every journey begins with a step.

I am very proud that this bin. When I add another weed lap in September, plus all the corn, cupplant, sunchokes, and sorghum stalks form the yard this fall, this cu yard of finished compost will be 100% homegrown.  As the gardens mature, I will begin getting leaf litter from the trees and willow and box elder coppice to add to it.  My gardens, minus paths, are about 3000 sq ft – that means that 4-5 cu yards could cover it all with .5″ of compost annually, which is alot if you are only maintaining fertility.  I can do that in about 5 years if I add more coppice trees; I am convinced that I can sustain the fertility of my gardens without additional inputs.

We can do this.

Be the change!

-Rob