Billy wrote:
....
Feel free to offer some citations for your responses, otherwise it is
just opinion, and you know what they say about opinions.


from _Permaculture_, Bill Mollison, 1990 p. 377


"SOILS

In drylands, any soil humus can rapidly decompose (in
dry-cracked soils) to nitrates with heat and water,
giving a sometimes lethal flush of nitrate to new
seedlings. Dry cultivated soils exacerbates this effect.
Mulches or litter on top of the soils prevents both soil
cracking and the lethal effect of rapid temperature gains
that cook feeder roots at the surface, so that in
subsequent rains there is less roots to absorb water.

Fire is destructive of this protective litter. After fire
and cultivation, most of the soil nitrogen, sulphur, and
phosphorous is lost, and even a cool fire loses plant
nutrients to soil water and leaching. When we know
more of the effects of fire in drylands, it is my opinion
that we will use any other method (slashing, rolling,
even light grazing) to reduce fire litter to soil mulch.
It now seems probable that Aboriginal burning has not
only gravely depleted soil nutrients, but caused a
breakdown in soil structure, and perhaps been in
great part responsible for the saltpans that preceded
agriculture. However, agriculture itself is a mon-
strously effective way to speed up this process and
intensify it."

an opinion from someone who wrote a primary text on
permaculture. it would be interesting to know what
observations he used to form that opinion. i've
yet to see anyone else make the obvious connection
between grassland burnings and soil depletion for
drylands. to me the thought upon seeing fires almost
anyplace is of all those nutrients going up in smoke.

the book has been interesting overall. i like many
of his perspectives and how to treat an area based upon
the limit of the water supply and that you cannot have
more people than the worst case scenario will support.
also he recognizes overgrazing as the most damaging
problem for many areas that are currently having
trouble feeding people. and like me he laments the
loss of the forests.


songbird