In praise of ramial chips, and other "waste" materials
by Tom Roberts
I get excited about chips. Not potato chips or silicon chips, but wood chips. I
believe they are a vastly underutilized resource on the organic farm.
Chips are coarser than the coarsest sawdust or shavings or shingle hair. They range
in size from a quarter to a slice of bread. In general, there are three kinds of wood
chips we might come into contact with: industrial chips, bark chips and ramial chips.
The first I call "industrial" wood chips, those which are produced by
disposing of old building materials, as a landfill or municipal transfer station might
do. Industrial chips may contain nails, putty, treated and painted wood, and other items
from old buildings. Nails can cause foot and tire injuries; pressure treated woods
contain leachable chromium and arsenic; lead can be present in old painted wood; other
materials can include broken glass, plastic shards, asphalt shingles,
drywall -- in short anything the workers down at the transfer station might
decide to toss into the chipper. These items make the chips both physically dangerous
and biologically undesirable. On the other hand, if you know the chippers and they
understand that the value of the chips they produce is dependent upon what they decide
to use as source material, you may find industrial chips useful. If you closely inspect
the chips in question, undesirable componants can usually be spotted rather quickly.
Although they have their place on an organic farm (like firming up woods roads), the
uses of industrial chips are few and they need to be used with care. In general, I
refuse industrial wood chips unless I am pretty sure of the source materials.
The second type is bark chips, often available from log processing facilities such
as saw mills. These make great mulches on many perennials, as the tanin in them makes
them long lived. Their dark color is also attractive. They are very low in nitrogen. You
do NOT want to till them into your garden soil. They are generally available only by
purchasing them either bagged or in bulk, either from the producer, garden centers or
nurseries. Ocassionally you can find an unwanted pile at a sawmill, where they are
considered a nuisance.
Ramial chips, though, are the ones that really excite me. Ramial chips are those
from trees and brush, from branches up to about 4 inches in diameter with or without
leaves. A fairly high percentage of their mass is thin young bark, young wood, and
I think of ramial chips as falling into three categories based on how to use them:
summer chips (with leaves), spring, fall and winter chips (without leaves), and
evergreen chips (with needles). And within these three categories there are
sub-categories, such as cedar chips (long-lasting, poor composters), or alder
chips (fast rotting, good mulch), and so on. Ramial chips are what I use most, so I will
from here on just refer to them as "chips".
After using chips in various experimental ways for several years, I was greatly
encouraged to read the article "Regenerating Soils With Ramial Chipped Wood"
in Dec. 98 - Feb. 99 MOF&G by Celine Caron, G. Lemieux & L. Lachance of Laval
University in Quebec. A search of the web primarily revealed these authors and their
work, which tells me there isn't a whole lot being written on using ramial chips. Work
by professor Gilles Lemieux and others at Laval University can be accessed via
http://www.sbf.ulaval.ca/brf/the_hidden.html, from which I quote:
"The first experiments where we spread and mixed ramial wood chips into the
top centimetres of soil have shown positive but rather startling results: while
productivity increased, there were major changes in the growth patterns and pathology of
common crops. We had to admit that we were facing a phenomenon on which there was no
mention in the literature. We could find no description of this part of the tree -
its branches - from a biochemical or nutrient viewpoint, and no attempt to relate
the different components to each other, even where these were known. (Lemieux, G. &
Lapointe, R.A. ).
"Branches of less than 7 cm in diameter contain lignin that is little
polymerized, or exists in the form of monomers, and also contain relatively little in
the way of hard-to-transform polyphenols, resins or essential oils. Field
observations and the literature both show that most ruminants will eat ramial wood, but
not stem wood. Insects, pathogenic fungi, bacteria and other life will also attack the
twigs. The effects of mineral deficiencies in a tree are most likely to appear first on
the leaves and young twigs. We concluded that ramial wood is indeed the tree's
"factory" for producing wood, lignin, polysaccharides, "oxides"
(glucose, saccharose, fructose, mannose, etc.), and proteins. It therefore represents an
important source of nutrients and energy for living things at all levels."
There is also a good book on using chips by Jean Pain, who composts them on the
Mediterranean coast of France. He chips in the rain when he can to assure the pile has
enough moisture, and runs black plastic pipe through the pile to supply his home with
hot water for months. Then he uses the rotted chips in his gardens. His book is
"The methods of Jean Pain : or another kind of garden." A Google search for
"jean pain" yields plenty of websites about Jean's work, mostly in French.
So, you can see there are two very different uses of ramial chips; tilling them
fresh directly into the soil, and composting them in piles. The most informative
articles, and where the most interesting research is being done, is in the incorporation
into the top layers of the soil. Composting chips means you are relying on the bacterial
microbe systems prevalent in garden soils, while direct topsoil incorporating or
mulching means you are investing in the far more complex fungal microbial systems
prevalent in forest soils. Often which you do depends on how chips best fit into the
management plan of your farm.
HOW DO YOU GET CHIPS?
You can make them either with your own chipper or with a rented one, available from
most equipment rental shops. Chipping is hard work on equipment, so it is best not to
try chipping any quantity with a light duty chipper like a Kemp shredder. You need a
piece of equipment whose primary purpose is to chip wood. We have a Finnish Patu 4400
PTO powered chipper that makes nice small quarter-sized chips out of brush up to
five inches in diameter. But be forewarned, it takes a large pile of brush to make a
small pile of chips. Which is great if you are looking to get rid of your brush pile,
but not good news if you are looking to manufacture lots of chips.
To encourage nearby folks to bring us material for composting, we have made a
brochure describing what items we accept at our farm, such as chips, leaves, grass
clippings, sawdust, etc. It can be viewed at our website
http://www.snakeroot.net/farm/WeWantYourLeaves.shtml. We leave this brochure at the
transfer station and the town office and hand it out at the farmers' market.
We have found the most productive way of obtaining chips is to stop at any nearby
roadside brush chipping that we see going on. Letting the crew know that you will take
ALL the chips they ever have makes their life easier, since once the truck is full of
chips they have to stop work because they have a disposal problem. We solve that
problem, and thank the crew with a few tomatoes, a bag of carrots, or some such gift
each time they drops us a load.
HOW CAN YOU USE CHIPS? LET ME COUNT THE WAYS. . .
Simply piled alone they store well, and in five years will look almost the same as
they day they were piled. Summer chips (with green leaves) will heat up and rot down a
bit, but there is so much more carbon in the chips than nitrogen in their leaves, that
the brief period of initial heating soon subsides. Of course this depends somewhat on
the type of woods being chipped, but getting more chips than you can use in a year or
two is no real problem if you have a place to store them. Piles of chips are very
porous, so they naturally tend to dry out quickly on their own unless covered with a
tarp, straw or hay, etc. Since drying is preserving, simple piles of chips don't
compost, they keep.
Winter and evergreen chips can be used to pave greenhouse and outdoor workspaces to
avoid the mud that would otherwise be underfoot. They make a soft, carpet-like floor
that is pleasant to walk on and stand on. Walking on a four inch layer of chipped spruce
boughs is a pleasantly aromatic for months.
We have spread chips with the manure spreader to pave our field roads to firm up
the surface on highly trafficked areas. They also make good fill for potholes and low
areas in farm roads, as the grass sends roots in and the chip fill is quickly part of
the surrounding ground. We have also used them on our woods roads to firm up wet areas
and filling in ruts.
As a mulch, chips need to be used with some forethought. As an annual mulch, where
the mulch will be turned under at the end of one season, a two inch layer of chips once
tilled under tend to tie up nitrogen for about a year. While it is acting as a mulch,
chips retain soil moisture, keep the soil cool, suppress broadleaf weeds, and encourage
earthworms. Alder or willow chips make the best annual mulch since they rot so
As a perennial mulch—even when used as a permanent mulch between beds
of annuals‐chips work very well on broadleaf weeds. For grasses, it is
best to use an underlayer—a heavy layer of cardboard or newspaper before
applying the chips. Either corrugated cardboard or cereal or pizza boxes work well, as
long as they lie flat and are overlapped at least 3-4 inches. For fewer seams, the
larger the pieces the better. For newspaper, be sure to apply it at least about 24
sheets thick, and be sure they lie flat. The reason it is important to have the
newspaper or cardboard lie flat is that you want to eliminate "windows" where
the grasses can easily grow through. So many layers of newspaper are needed to provide a
sufficient barrier to the roots of grasses. If existing grasses or weeds make the area
too lumpy, an initial weeding or close mowing may be necessary—use a weed
whacker or lawn mower. To make it easier to get your cardboard or newspapers to lie
flat, get them soaking wet. Either leave them out in a heavy rain or soak them in a tub
or wheelbarrow overnight.
Be forewarned that newspaper expands about 50% when soaked, so if you fill a 5
gallon bucket with newspapers and add water, the next day you will spend the better part
of an hour getting them out. If you are using the rain-soaking method, remember that
even a heavy rain will only soak through about a half inch of newspaper, so spread them
out for their rain soaking. Or toss a bundle of newspapers into an unused corner of the
garden or under the house eaves, to be used in a month or two. In the fall, we have left
an eight inch thick bundle of newspaper outdoors where they were to be used for mulch.
The next spring, some of the middles of the center papers were still dry.
Once you have a good supply of wet newspaper or cardboard, pave the area to be
mulched with them, overlapping a good 3-4 inches. This always takes more material
than you think it would, but don't skimp. An additional advantage to soaking this first
layer means you can cover a large area without fear of the wind blowing it away. Once
you have a section mulched, start pouring on the chips.
Enough chips should be used to at least completely cover the underlayer, but the
more the better. Think 3-4 inches. Make sure the chips completely cover the edges of
the underlayer, as well. What will now happen is that the top layer of chips will
protect the underlayer from drying out, and it will gradually decompose from microbial
and earthworm action. This will take about a year, and in the meantime most of the
grasses will die. It still amazes me, after applying a thick layer of newspaper, to poke
a hole through the chips the following year to find hardly a trace of the underlayer
left. Any grasses that do poke through the next year will probably be rhizome grasses.
These will be easy to pull up along with their long rhizomes, as long as you do it early
and don't let them establish a huge mass of rhizomes. Many of these will not actually
have originated from the mulched area but will be invaders from surrounding unmulched
sections. To deter this, several times a season we rototill around the edges of the
garden to keep these invaders at bay.
Young and old apple and pear trees like a chip mulch, at about four to six inches
thick. Keep them one foot from the trunk and go out to the drip line. Since we grow
peppermint and spearmint under our trees, and since grasses don't do well under trees
anyway, we don't use an underlayer under our fruit tree mulches.
All of the work done on building soils with ramial chipped wood recommends tilling
the chips directly into the soil. I have done this sometimes, usually followed by a
cover crop. When tilling in two inches of popple chips, I have found that there are
temporary (one year) signs of nitrogen deficiency (poor crop growth, small plants with
yellowing of leaves). By the second year these signs disappear. This may have been due
to the large amount used, and the fact that some of the branches chipped were rather
large. In future, I will be doing more direct tilling of chips into the soil using
popple, alder and other mixed woods in separate sections, and chipping smaller diameter
wood. The research quoted above has shown that ramial chips from climax trees (oak,
maple, yellow birch, beech) produce the best quality soils, while ramial chips from
conifers are the least beneficial.
Mixed with cow manure, chips take more than a year to digest, so we no longer use
them this way. However, over the past two years we have discovered that grass clippings
have the necessary nitrogen to make chips "disappear" within a year when mixed
at the rate of one grass to two chips and turned a few times. Such piles get VERY HOT
very quickly. This past summer's pile is six feet high and thirty feet long and could be
seen emiting warm vapor in the cool of morning and evening.
How do we get so many grass clippings? Organic farms should be the end of many
waste streams, and the beginning of few. We get two to three pickup loads a week by
letting a lawn care business know we will take all he has "any daylight hour seven
days a week". We have even given him some "$2 Thank-You Coupons" good
at the local farmers' market to hand out to his lawn care customers. On the coupon we
explain that the customer's clippings are going into our compost pile to grow our
vegetables, so we are thanking them for helping us grow our crops.
It is important to develop a good relationship with various potential suppliers of
organic materials to your farm. Quite often the very materials they undervalue are
exactly the ones you need, but this must be explained to most people. These
relationships and educational conversations become part of the bonding between the farm
and the community.
One of the design aspects of our farmyard we integrated into its contruction was a
large turn-around area, where cars, pickups and chipper trucks, even with trailers,
can manoever with ease. We feel it is important to assure that folks who are good enough
to haul in free materials should have an easy time of it at this end. It is part of our
"pay" for having dozens of folks "working" for us by gathering and
delivering their organic matter.
Homeowners can supply leaves and grass clippings. Professional leaf rakers can
provide whole and shredded leaves and pine needles. Local dairies can provide bailing
twine for trellissing, mulch hay and, of course, manure. Often manure that has hay mixed
with it is not good for spreading on hayfields because the clumps of old hay will
interfere with this year's mowing, so dairy farmers are glad to get rid of it.
Municipal transfer stations can be sources for leaves, and will often direct
residents to your farm for disposal of the bulky organic "waste" products they
find so hard to dispose of. An excess of leaves is no problem either. We have a
"leftover" leaf pile now five years old that is the source of much valued leaf
mold we use in our potting mix and greenhouse planting beds.
Alders are great candidates for chip making, since many farms have access to wet
areas where alders are abundant. They resprout quickly, so that five to seven years
after harvest, they are ready to harvest again. Alders have nitrogen fixing bacteria
growing on their roots, so they are able to derive nitrogen from the air. This enables
them to grow in nitrogen-poor areas, but it also means that harvesting them allows
you to access an otherwise unavailable nutrient source. I have used alder chips as mulch
and as an addition to compost; they rot so fast that there is almost no trace of them
the following year.
Tom Roberts has been
farming organically since 1980. Tom and partner Lois Labbe currently grow vegetables and
herbs on 2 acres of fields and four greenhouses at Snakeroot Organic Farm in Pittsfield.
Their farm tour day is the second Sunday in July each year.