> -----
> From: Jay FitzGerald
> Sent: Sunday, June 28, 2009 5:28 PM
> Awesome, but I expect that'd not enough loading to really show an effect.
That's a good question. As you can see on my notes under 'Applying to the
Soil: How Much?', application rates for a large number of published tests
seem to have been in the range of 5 to 30 tonnes/hectare, which is .5 to 3
kg per square meter. I chose 2 kg/m2 for this test, which is in the high
end.
> Besides, at this point, it only pulls nutrients, right?
Also a good question, but as they say, soil is an endless science. :) Which
is to say, it's potentially far more complex. We get 80-100 inches/year
rain here, and it's entirely possible that the rain will leach away some of
the NPK from the control plots, and leach less from the char plots, which
would give them a plus. It is also possible as you say that the char will
absorb the NPK, and not give it back until the soil biology develops
sufficiently (sometime later). That's already a familiar effect here with
the acidic clay soil itself, which as Dr. Deenik once explained (if i
understood properly), is derived from weathered volcanic ash, it has a very
high surface area and high CEC, which should be a good thing, but the first
load of fertilizer you add gets largely 'soaked up', trapped in the clay's
fissures, and it's hard to get back.
There are also the numerous published tests, particularly on tropical soils
such as those of Christoph Steiner, e.g.:
'Nutrient availability and leaching in an archaeological Anthrosol and a
Ferralsol of the Central Amazon basin: fertilizer, manure and charcoal
amendments'
http://www.css.cornell.edu/faculty/lehmann/publ/PlantSoil%20249,%2034...
202003%20Lehmann.pdf
showing results in order: Control < Char < Char+Fert. In those soils the
presence of the char /alone/ gave an advantage (possible just by raising
soil carbon, enabling microbial life to thrive and benefit the plants.)
In short, there are so many factors; that's why we test. :)
-Ben
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