Subject: [Homestead] Composting large wood chips---it's hell to do.
Date: Sat, 06 Nov 2004 13:32:59 -0800
A nine horsepower MacKissic chipper-grinder with a three-quarter inch
screen would make composting a matter of a month or so, with 30% carbon
wood chips ground to one-quarter to three-eighths sife, and one percent
nitrogen from any source, kept well wetted---and turned every couple
weeks if you have a front-end loader.
Large wood chips from a road crew or municipality tub grinder, are
sl-o-o-w to compost, may take four to five years, wirth no more than
one-third of biomass composting the first year, so if you have a nearby
chicken or turkey farm, they may do you (and themselves) a favor by
dumpiong their manure on your large-chip pile so you can borrow your
neighbors front-end loader to turn the pile occasionally.
(condensed from a discussion supplied by Ferry County Solid Waste)
*Wood Chip Carbon and Nitrogen*
The micro-organisms that decompose wood chips require nitrogen in
amounts greater than are available in the wood chips alone. If
additional nitrogen is not mixed with the wood chips, the
micro-organisms will get the nitrogen they need from the soil, competing
with plant roots for the nitrogen available in the soil. This is why
bark mulch works to keep weeds down.
*Wood Chips in Compost Piles:*
Most of the material you place in your backyard compost pile is high in
nitrogen. Food waste and lawn/garden waste are the two most common
ingredients of backyard compost piles, and both are high in nitrogen.
Wood chips can be added to a compost pile to provide a better
carbon:nitrogen ratio. Wood chips, with their rigid structure, also
enhance the flow of air through the compost since they are less prone to
compact. This is a good thing.
*Wood Chips as a Soil Amendment:*
You can use wood chips to add organic material to soil. The process will
take four or more years. You will need to add nitrogen along with the
wood chips to facilitate decomposition of the wood chips without
depleting the available nitrogen in the soil.
For each 10 X 10 area:
Year One: add one pound of ammonium sulfate for each one inch layer of
wood chips.
Year Two: add one half pound of ammonium sulfate for each one inch layer
of wood chips.
Year Three: add one quarter pound of ammonium sulfate for each one inch
layer of wood chips.
Year Four: add one eighth pound of ammonium sulfate for each one inch
layer of wood chips.
In other words, start with one pound ammonium sulfate for each 100
square feet the first year, and decrease that amount by half in each of
the following years, until the wood chips are fully decomposed.
*Wood Chips and Soil pH:*
Wood chips will lower soil pH, making it more acid. That is a good thing
for acid loving plants like evergreen trees and shrubs, but might be bad
for other plant species. In areas where soil is already neutral or acid,
the addition of wood chips can result in excessively acid soil.
*Wood Chips Miscellaneous:*
A layer of wood chips will help hold in moisture once it reaches the
soil, but in low moisture areas it can prevent dry site adapted plants
with extensive surface roots from getting moisture through dew and light
rains.
Depending on the type of trees, wood chips can also release tannins that
may be toxic to some of the soil organisms.
*Caution:*
For the reasons stated above, you should not spread wood chips directly
on, or till them into, a vegetable garden or other areas where you want
seeds to germinate. Wood chips are great around established shrubs where
denitrification of the surface soil will inhibit germination of weed and
grass seeds.
*Benefit:*
Next time you drive by our office take a look at the shrub bed along
Grant Avenue. It is mulched with wood chips from our local brush site.
Note also the tax savings from reduced maintenance. No need to weed for
the last two years.
*Compost, Wood Chips and Carbon:Nitrogen Ratios*
Wood chips have an average C:N ratio around 600:1, but only the outer
surface of the wood chip is really available to react with the microbes
in the compost pile. In practice only about 1/3 of the wood chip will
decompose in a 3-6 month composting period. So, when determining a
compost mix, only count 1/3 of the stated C:N ratio. Wood chips, with an
average C:N ratio of 600:1 would be mixed in as though they had a C:N
ratio of 200:1.
Later, when you screen out the partially decomposed wood chips they can
be added to the next batch of compost. In fact, adding the partially
decomposed wood chips to a new mix will help innoculate the new mix with
the microbes necessary to activate the compost pile.
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Date of Source Material: 1/26/2001
Source: Klickitat County Solid Waste
Link to Source: Klickitat County Solid Waste:
SolidWaste AT co.klickitat.wa.us <mailto:SolidWaste AT co.klickitat.wa.us>
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