Mulch ado about nothing

Biochar, one of gardening’s new wunderkinder, is what remains after you burn wood with insufficient air – charcoal, that is.

People are funny. Take, for instance, a fellow gardener who, a couple of months ago, shared with me her excitement about a biochar workshop that she had attended. “I can’t wait to get back into my garden and start making and using biochar,” she said.

Biochar, one of gardening’s new wunderkinder, is what remains after you burn wood with insufficient air – charcoal, that is. Stirred into the soil, its myriad nooks and crannies provide an expansive adsorptive surface for microbes and chemicals, natural and otherwise. Biochar, being black, darkens the soil, and dark soil is generally associated with fertility, although that’s not always the case. Because biochar is mostly elementary carbon, it resists microbial decomposition, so its carbon is less apt to end up in the atmosphere as carbon dioxide.

But raw wood, as opposed to biochar, added to soil feeds microbes and then plants as it decomposes, eventually turning to organic matter, or humus, which is a witch’s brew of compounds with positive effect on soil’s nutritional, biological and physical properties. So is cooking up a batch of biochar and digging it into your soil really worth the effort?

The same might be asked of aerated compost tea, another “rare and wondrous” product touted for everything from preventing plant diseases to breaking up impermeable soil layers; or “nutrient-dense farming,” which, with its questionable assessments of plants’ nutrient status and even more questionable soil additives, aims to reverse the drop in mineral concentrations noted in our vegetables over the past few decades (even though the drop has been shown to be simply a dilution effect from increased yields due to breeding, fertilizers and water).

Thoreau wrote, “Simplify, simplify.” But people are funny; they want to complicate, complicate. Something about using some apparatus, whether it’s a biochar burner or a compost tea aerator, or a measuring device, such as the refractometers used by nutrient-dense farmers, draws people in. People are wowed by numbers, dials and other bells and whistles of science.

Bells and whistles do not science make – or good gardening. Some of the most elegant experiments in the science of gardening involved not much more than a human mind and some pea seeds: the 19th-century discoveries of heritable traits by Gregor Mendel, which became the foundation of modern genetics, and the elucidation of why plants bend towards light by Charles Darwin, as examples.

Ninety percent of good gardening could be summed up in two words: organic matter. Enrich your soil with plenty of compost – the Cadillac of organic matter – and/or other organic materials, such as leaves, straw and wood chips, and you’re well on the way to plants that are healthy, healthful and productive. I wish that I could offer some gimmick or catchphrase. No need.

I finally cut enough hay to snuggle down along my row of dwarf apple trees. Right now, it looks like a billowing beige blanket. By spring, snow and rain will have compressed it to ground level. By this time next year, it will be mostly gone. That’s okay.

During its tenure, the mulch will smother weeds and insulate the soil against winter cold and summer heat. Bacteria, fungi and other soil organisms are what will make it vanish; but in so doing, nutrients within those stems and leaves will move into the soil for plant use, and what’ll be left behind is humus, which makes the soil dark and, in this case, is an indicator of good soil.

Some garden faddists would fault me for using hay beneath my apple trees, alleging that the trees would prefer a mulch of wood chips – and not just any old wood chips, but those from branches less than two-and-a-half inches across (“ramial” wood chips). Devotees cite Laval University Publication N 83, Regenerating Soils with Ramial Wood Chips, as providing evidence for the benefits of ramial wood chips; but this publication is actually very weak on evidence and very strong on boosterism. Perhaps they are correct, although there’s no evidence for benefits one way or another. Depending on availability, I’ll sometimes use wood chips – any kind. Simplify, simplify.


Any gardening questions? E-mail them to me at [email protected] and I’ll try answering them directly or in this column. Come visit my garden at For more on local homes and gardens, go to Ulster Publishing’s



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  1. Like most things I read about gardening on the Net, I agree with some of what is written, but seldom all. This article is no different.

    RE: biochar - biochar serves a different purpose than adding organic matter to the soil. Whether or not it is worth all the excitement remains to be seen, but its supposed function is to provide a haven for microbes in the soil. Organic matter serves to provide a readily available carbon source for microbes in the soil and to serve as a reservoir to hold nutrients in the soil by increasing the CEC. So don’t dis biochar until we know all there is to know about it. You are comparing apples to oranges.

    RE: AACT - this one is also maybe correct maybe not, depending on what type and quality of compost is being used. The idea behind AACT is to extract the microbes from GOOD quality compost, add a food source and maybe minerals and increase the DO so support the increased population of the microbes. They are then sprayed on the soil as well as on the leaf surface to protect the plant AND to feed the plant. It all depends on how well the equipment works and how good the original compost is.

    A better solution is to make vermicompost tea and spray it on the leaves like you would a foliar. If it is good vermicompost it is easy to use, effective and the residue can be added to the garden. And of course straight vermicompost can be added to the soil as well.

    So, sometimes things just aren’t that simple and sometimes they are.

  2. The first comment provided by michaellabelle is a good basis to work from.
    I like to suggest that Lee Reich could learn a lot more with an open mind rather than being dismissive and somewhat cynical.
    I am all for not complicating things but there is a lot to learn from others.
    The ongoing international Terra Preta research and findings may assist many around the world to achieve optimum soil and nutrient conditions.
    There is a lot of valuable information available and we continue to discover things that had not received the attention they deserved in the past.
    Look for example at the Oekoregion / Eco-Region Kaindorf in Austria as a holistic initiative. Here we can all learn from a positive community sharing where anyone can provide and receive valid information for a better future in various ways.

    Gerald Dunst and his Sonnenerde team (SunSoil) for example just received the Austria 2012 Climate Protection Award from 335 original proposals.
    Technology makes it possible to share this with you and this may lead to more.
    Here a video link in English:
    Positive thinking - happy, healthy living.
    Cheers from Tasmania

  3. Any discussion of biochar should reference the International Biochar Initiative (I.B.I.) at Cornell University, which attempts to gather all research and articles on the subject. One article suggests that burying enough biochar to return to the CO2 levels of our planet at the 2004 levels will require sequestration of 7 billion tons per year. This will require a great deal more than casual backyard experiments, and must begin sooner than later. Biochar, horticultural charcoal, etc. are not a process of burning, but rather a process of cooking. Using fossil fuel to cook this product would be silly and counter-productive. We are producing a product of high-quality vermicompost made from organic waste blended with biochar, for the retail market, and would encourage others to do the same. One cup of this blend mixed with a cubic foot of potting mix will produce remarkable results. Making vermicompost tea with a cup in 5-gallons of water will inoculate the biochar and provide a rich liquid organic plant food. When trees die and decompose they return CO2 to the atmosphere, so burying live wood in the ground fails to accomplish a favorable sequestration result.

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