[Homestead] Soil and fertility
frank.fries at imagewireless.ca
Sat Jan 24 21:17:22 EST 2009
> out, it seems, that the charcoal is incidental. The archeology of the
> show that they were intensively gardened continuously for 3000 years and
> why they are permanently fertile. >
Having read a fair bit on this, and having read about the various
experiments in pots with differing percentages of charcoal, etc. it doesn't
appear that anyone really knows why the soil is permanently fertile....
however, as you said, just adding powdered charcoal definitely doesn't do
In the Amazon basin, when they dig some of the Terra Preta up, as long as
they only take a little at a time and leave enough in the patch, it seems to
"grow back"... This implies that it is related to beneficial
micro-organisms... There is some speculation that the porous nature of the
charcoal helps by providing a beneficial environment for the soil
In one case that I read about (it was a while ago and I don't have a link to
it - this is from memory only) they tried a number of patches in the Amazon
basin, in the poor soil - a control plot (no change to the soil), a plot
with chicken manure added, a plot with charcoal added and a plot with
chicken manure and charcoal added. (I think there were actually a number of
plots in each of the categories above, with varying amounts of manure and
As you would expect in infertile soil, the plot with the chicken manure
added did better than the control plot. It also did better than the control
plot in the second year but the improvement was less marked and even less so
in the third year.
As I recall the plot with the charcoal added was slightly better, but not
much so compared to the control plot.
The plot with the charcoal and manure was approx. the same as the chicken
manure plot the first year, but noticably better the second year and even
more so in the third. There appears to be a cumulative effect. This may
possibly be due to micro-organisms getting a chance to breed up and perhaps
the charcoal assists in some way.
None of the above is conclusive and it certainly doesn't necessarily mean
that the same thing would work here...it is possible for example that there
very specific micro-organisms that exist there and not elsewhere, or ...??
Another thing I once read was about the beneficial effect of animals on
soil. I think everyone (even the agri-biz soil scientist types) agrees
that organic matter added to soil is good. At the very least, it produces
nitrogen. There have been studies proving the negative effects of cropping
land and taking all organic residues off (the straw, stalks, etc).
In the study I read about, they used a number of fairly large plots that had
been farm land, and they seeded all but one of them to some kind of forage.
The unseeded one was kept fallow.
In one plot they just let the cover crop (hay/grass) grow and stay on the
land, eventually decomposing ( I can't recall for sure, but I think they may
have cut it and/or chopped it).
In another, they harvested the hay (and hauled it away).
In yet another, they harvested the hay and fed it to animals, whose manure
went back on the soil. I can't remember for sure but I think that they let
the animals harvest it directly (graze), which of course also looked after
spreading the manure.
So on the one plot, nothing was taken away from the soil, on the second, the
weight of the hay was taken away, and on the third, the weight of the
grazing animals turned into meat was taken away from the soil.
If it were just volume of organic material, you would expect the piece with
nothing taken away to be the most fertile after the trial. As I recall, all
the seeded test plots were more fertile than the fallowed plot after the
trial and the most fertile was the one that had the animals and their
manure. It appears that perhaps the digestion process used by animals adds
benefits beyond just the organic material in the manure.
It appears to me that none of this is just cut and dried, and as the soil,
moisture and weather changes from one area to another, different rules
apply. It sure is interesting though.
I look forward to experimenting with different things over the next few
years as I get a chance to.... One of the things I mean to try is raised
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