This year I revamped about half of my garden space using the biodynamic method found in John Jeavon's material. I now have the other half and after seeing the Back to Eden film I am really intrigued by using this method.
I have already tracked down some suppliers for recycled newspaper and (free) woodchips, now I just wanted to know if anyone has given this a try and if they have been able to emulate the almost too perfect to be true results that Paul Gautschi is getting as shown in the movie.
It really matters what kind of wood chips you're trying to use. The wrong sort can doom your gardening project.
Wood chips and sawdust from large diameter limbs, trunks and Evergreen trees kind of suck the nitrogen out of any environment they're used in. Their Carbon/Nitrogen ratio can run from 400:1 to 750:1. It has to do with the decomposition process and the bacteria and fungi that decompose wood. They need nitrogen to create protein and will remove it from the soil to try digesting the woody materials. Evergreen content also introduces a lot of tannins, substances that are used by these trees and shrubs to control plant growth underneath their drip-line and can stop plant growth till they've been broken down by soil bacteria.
Usually composting wood chips works best if you take something with so much nitrogen content it will burn plants (chicken manure) and mix the two together to compost both into a usable soil amendment.
As a mulch, wood chips can be effective, just don't till them into the soil for the above reason. Rake off at the end of the year, sow your cover crop for over wintering.
True Ramial Wood Chips are supposed to be new growth, small branches and tree top wood from deciduous brush and trees with the diameter not to exceed 7cm/2.75". The name comes from the Quebecois term "bois raméal fragmenté" or in English, "chipped branch wood". This is all from the parts of the trees and brush that are still growing, contain soluable unpolymerized lignins and high quantities of nitrogen, phosphorus, potassium, magnesium, calcium in the cambium and bud tissues.
Because of the Carbon/Nitrogen ratio in Ramial Wood which averages 30:1 and if larger diameter branches are included can go up to around 170:1, we're dealing with a much different product from wood chips. The various studies in Ramial Wood agriculture often add Blood Meal (about 13% Nitrogen) to add a little extra nitrogen to the mix to make up for the higher Carbon/Nitrogen ratio in the larger branches.
Why Ramial Wood Chips work:
You are starting off with a nutrient rich mulch that has a high content of unpolymerized lignins and enough nitrogen to not deplete the soil. The unpolymerized lignins require no breaking down to become a ready food source for soil fungi that quickly absorb it and proceed to break the rest of the wood content down into soil humus. This also starts liberating the nutrients that beneficial soil bacteria require.
If you're growing fruit trees you will find Ramial Wood Chips to be a ground mulch that also provides nitrogen in an ammonia based process due to the soil environment it creates, a source of nitrogen better adapted to tree growth. Shrubs and trees prefer ammonia, not nitrates.
Bark chips make a good mulch, but in densely planted areas, best to add some nitrogen to the soil beneath before spreading the mulch if you are not using a membrane, and in particular if the mulch is applied during spring or early summer. Woodchips are best composted, certainly for a year or so before use, unless you're prepared to rake them off every few months and reapply nitrogen to the ground so that your plants do not go short. If the area isn't planted, and the woodchips are just being used to suppress weeds, then nitrogen shortage won't be such an issue.
I haven't seen the movie, but there are no shortage of studies or "studies" singing the praises of ramial wood chips. Here's one: http://www.mofga.org/Default.aspx?tabid=850
Trees seemed to grow tallest and soil organic matter increased most when RCW was used both as a mulch and was incorporated into the soil. The increase in organic matter is most encouraging. This sandy loam has been extremely low in organic matter, and cover cropping, adding manure and compost have not changed the organic matter as much as two years of RWC applications did.
Here's another: http://www.uvm.edu/vtvegandberry/Pubs/Wood%20Chips%20in%20Vegetable%20Production.pdf
Wood, really, is just cellulose (C6 H10 O5) which turns into CO2 and H20 in time. Wood has a few minerals. I can only speculate on why wood seems to work so well. Humus is probably one reason. Wood is a buffer for water (soaks up excess and is a source of water in dry periods). Wood is dense, so it breaks down slowly, which is less of a nitrogen leach than leaves would be.
In my personal experience I have found bulldozed piles of topsoil containing trees which rotted down for almost 10yrs to be excellent soil. Basil planted in that soil is 3 or 4 times bigger than that planted in plain topsoil. The soil is also loose and light, instead of the normal heavy sticky clay I have natively. This indicates (to me) that the soil has been replenished with calcium... apparently from the wood. Wood ashes are roughly 30% Ca, 10-15% K, and 7% Mg for pine and oak. http://www.fpl.fs.fed.us/documnts/pdf1993/misra93a.pdf
