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 sometimes leaves.

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/regenerating_soils_98.html and 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. [1986]).

"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 quickly.

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.

NOTES:

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.

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