[Terrapreta] charcoal in soil experiments
Tom Miles
tmiles at trmiles.com
Wed Apr 18 12:07:34 CDT 2007
Richard,
Great description, thanks.
Tom
-----Original Message-----
From: terrapreta-bounces at bioenergylists.org
[mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of Richard Haard
Sent: Wednesday, April 18, 2007 9:32 AM
To: terrapreta at bioenergylists.org
Subject: [Terrapreta] charcoal in soil experiments
Discussion group -
Very good discourse on experiments with charcoal in agriculture. For
your reading interest, this is the point I am at in my own container
testing project at 4CN. Comments and suggestions are always welcome.
My own experimental setup is scheduled to be launched by end of month
at latest. I have already started my test subjects in 4x4 containers
and their roots/shoots should be active when I start.
This weekend I am laying out and calibrating my irrigation system
and I will be using the same rate of watering as our seedbeds in the
adjacent fields. We will have tensometers in place to be sure we only
water when needed. Dr Steiners comments are very interesting and
helpful at this point as I need to decide on rate of charcoal use in
the pots. I am planning to use charcoal at a high rate because this
is a screening for effect and not a dose related study. Present plan
is to use 30% on v/v basis but am interested to see what this
discussion reveals.
Another factor I will need to mitigate is pH changes brought about
by the charcoal. Our farm soil is running pH of 6.6 and need to keep
everything at this level or below. I noticed in the Georgia master
gardeners study they used sulphur to adjust pH downwards and am
thinking I may need to do this too.
The soil at our farm is a different chemical profile from that
mentioned by Christoph in Brazil. We have a sandy loam that is
highly leached, has medium to medium low phosphorus, very high
potassium (probably due to glacial origin as unfarmed soil nearby is
same), very high calcium, medium magnesium, low or nil nitrogen.
Organic matter is about 4 to 6% or about midrange. So far as trace
elements Copper, Boron ,Manganese, Iron and Zinc are at the low end
of the range. Our fertilizer mix is formulated to match these special
trace element needs as well as our major element requirements and is
the same as our farming operation uses.
I am conducting soil tests and foliar analysis this year at the
University of Mass, soil testing lab. Their reports come with
recommendations, are very easy to read and come with a squib to
explain what each test means. Each test, with organic matter costs $13.
Also interesting to study is the cation exchange capacity and base
saturation in this soil testing regime. The CEC is a measure of the
soils ability to retain and supply nutrients. Our CEC, 11 to 12%
probably represents our relative low organic matter and content and
also % base saturation of 4 +%K, 6-10% Ca, and 48 - 61 % Mg are
measures of adsorbed cations in our soil.
I will be looking at these data points, especially soil nitrogen in
my various treatments. Measuring the effect of treatments is always
troublesome for me and numbers like these will be helpful when I am
trying to interpret plant yields.
My main interest is to learn if a container test can be useful to
evaluate our farm soil management practices and therefore am using
soil that has been cropped in a 2 year cycle and using no fertilizer
in the control. Normally for a 2 year (2-0) crop we use a single
treatment of fertilizer in a pre-planting treatment, with sometimes
compost incorporated. During the growing season we use a light
treatment with urea to stimulate early summer growth.
What is interesting to me is to see what effect charcoal will have on
this management regime, not only for a single season but to save the
soil for another second crop the next season without additional
supplements. To take this extended view I figure i need a high
volume of soil so i am using 4 gallon pots. As these plants are a
woody shrub and a perennial we will run the test until after killing
frost.
There will be 300 to 380 pots in my project.
Best
Rich Haard, Fourth Corner Nurseries, Bellingham , Washington
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