Re: no-till gardening
Tony & Moira Ryan wrote:
>
> Richad Starkeson wrote:
> But the compost on top of the soil method will take a good deal longer
> > than working it into the soil to some depth, and it won't be amended as deep.
>
Hi Richard
Strangely, and against all received wisdom and common sense both
individual observations and formal experiments disagree with you in
this.
Field-scale trials in Israel a few years ago were done to find our
which
was the best way to incorporate organic matter (compost) in soils. They
compared conventional ploughing, rototilling and simply applying the
compost to the surface.
They found that the surface application was in fact the most effective
and the ploughing the least, both in the general amelioration of the
soil texture and the depth of the improvement. After three years on the
undisturbed plot traces of the added organic matter were turning up in
the lower soil a full metre below the surface, well below those in the
other treatments.
As to more informal observations, at least with clay soils we have had
many people on the organic list talking of how they tried
unsuccessfully
for years to improve their gardens by digging in organic matter, and in
despair finally built beds on the surface instead - only to discover in
a very short time a rapidly-developing depth of good usable soil in the
underlying clay.
In fact it is possible to offer a logical explanation. As nature has
only very limited means of digging soil apart from areas with burrowing
animals, she has had to develop a mechanism for incorporating into the
soil materials which accumulate on the surface. To accomplish this a
very complex organisation involving all sorts of soil inhabitants has
evolved and these inhabit the surface layers of the soil. I must stress
the word "organisation", as it is evident they do not act randomly but
work together like people in a factory. There is definite structure in
an undisturbed soil with such easy-to-see features as the burrows of
such creatures as worms and ground beetles and many smaller pores we do
not usually notice. This open sponginess of the topsoil/mulch layer is
held in place by natural glues produced by certain fungi and other
organisms and is quite firm and elastic enough to resist destruction by
such things as normal treading. Associate with the soil structure are a
great variety of microorganisms, chiefly (but by no means exlusively)
bacteria and fungi. These each have their own working space and
preferred soil level and if undisturbed are amazingly active in dealing
with organic matter falling on the surface and turning it into useful
humus.
It does not take a great deal of effort to picture how drastically this
peaceful scene of industry can be disrupted by the spade or (even
worse)
the tiller. Not only are the main structures of the surface soil
destroyed, but many of the inhabitants are likely to be killed, not
only being physically chopped (worms mostly) but by being either buried
to deep to survive or conversely being exposed on the surface. In fact
digging seems to be particularly disruptive on clay soils. While loams
will apparently recover their structure after several months, clays
seem to be more sensitive and very often revert to a wholly intractable
state.
Moira
--
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata, New Zealand. (on the "Ring of Fire" in the SW Pacific).
Lat. 41:16S Long. 174:58E. Climate: Mediterranean/Temperate
