[Market-farming] soil fertility continuing ed
William H Shoemaker
wshoemak at illinois.edu
Mon Mar 21 12:07:22 EDT 2011
I'm going to be the friendly skeptic on biochar. I don't know enough about
it, but I have questions about its utility in temperate zone soils.
If I understand correctly, it works by creating exchange sites for holding
nutrient ions in the soil. In other words, charged nutrient ions are
attracted to oppositely charged sites in the biochar. These biochar sites
then release amounts of the nutrients to create an equilibrium of available
nutrient ions in the soil solution. The released nutrients are available for
plants to consume.
The idea of exchange sites is critical for fertile soils because they're
like bank accounts. Withdrawals are made as needed to maintain nutrient flow
into the soil solution, where plants have access to the nutrients. Where
biochar was discovered, in the Brazilian tropics, the soils are almost
sterile because they're so washed out and organic matter just deteriorates
rapidly in the constant heat. The biochar then becomes an exchange site
resource for soils that wasn't there previously. It makes a great
difference, at least temporarily, in those soils.
In temperate zone soils, we have two other resources that provide lots of
exchange sites in the soil. Certain clays, like montmorillonite and illite
are two examples. Soils with these clays have high CECs (Cation Exchange
Capacities), or lots of charged sites for attracting and holding nutrients.
We also have accumulating organic matter because we have cold seasons that
slow the breakdown by biological digestion. As OM breaks down into
fundamental tissues like humus, it not only releases nutrients that
originated in the organic matter but it creates exchange sites on OM
particles. So these are critical reasons why temperate zone agriculture is
so important to feeding the world. The soils in these regions have ancient
organic matter that helps facilitate nutrient availability.
So I wonder if we really need, or benefit from biochar in the temperate
zone? I suspect it's a great technique in the tropics but I'm a little
skeptical about it in the area most of us grow our crops in. I actually have
become less concerned about nutrient management over the years than I have
water management in crops. Water is the bulk of crop tissue (>90%) in annual
plants and is key to nutrient availability and transport into roots. I've
found that in our soils if water is maintained optimally that it has a
bigger impact on yields and quality than nutrient management. That's one
reason I love drip irrigation.
But anyway, I'd be curious if others have different views on biochar in the
Midwest or temperate zones generally. We all farm in different places and
may need to do different things to be successful.
William H. Shoemaker
Sr. Research Specialist, Food Crops
University of Illinois - Crop Sciences
St Charles Horticulture Research Center
535 Randall Road, St Charles, IL, 60174
wshoemak at illinois.edu
From: market-farming-bounces at lists.ibiblio.org
[mailto:market-farming-bounces at lists.ibiblio.org] On Behalf Of Steve Diver
Sent: Monday, March 21, 2011 10:31 AM
To: Market Farming
Subject: Re: [Market-farming] soil fertility continuing ed
Lump charcoal (vs briquettes) is the kind to get started with, yes.
E.g., Cowboy Charcoal
Btw, "The Biochar Revolution" edited by Paul Taylor which just came
out recently is the hands-on book for practical biochar.
On 3/21/2011 10:04 AM, Ann Sherrington wrote:
> At the risk of sounding simplistic, I have a question on biochar: if
> biochar is based on charcoal created in a smothered fire, does it
> follow that you could take commercial charcoal (not the briquettes,
> the "real" stuff), pulverize it, add it to your soil, and get a
> similar effect?
> Ann Sherrington
> Cape Breton
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