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  • From: "Tradingpost" <tradingpost@lobo.net>
  • To: livingontheland@lists.ibiblio.org
  • Subject: [Livingontheland] No-Tillage
  • Date: Sun, 28 Dec 2008 13:12:40 -0700


No-Tillage
Whole Systems Agriculture
October, 2004
http://netptc.net/flowermanoat/wSAgHTM/Pages/notillage.htm

Since tillage is one of the more threatening agricultural practices to
sustainability, it is a puzzle to me how production systems that include
tillage can also claim to be sustainable. Its practice goes back more than
6000 years to the very dawn of agriculture. An historical review of
civilizations that have flourished and crashed over this time will reveal
that virtually all of them either depleted their own soil or were defeated
in resource wars focusing on food; which is to say, soil. In 200 years of
European style agriculture, the United States has lost a third of its
topsoil to erosion by wind and water--a direct consequence of tillage and a
fact known by just about every student who has taken an agriculture course.

Less known is the depleting effect tillage has on soil organic matter
because of oxidation resulting from the admission of air by tillage. This
oxidation, that is the burning up of organic matter, releases lots of
soluble nutrients so farmers get good immediate results at the expense of
the soil’s long-term, stored-up fertility. This is just like withdrawing
money from a savings account and never replacing it. This might not be so
bad if all the released fertility was utilized by the crop, but
unfortunately that is not the case; often more of these nutrients are lost
to leaching than are actually used by the crop. Many people believe that
all we need to do to be sustainable is return the nutrients lost by
cropping, but this cannot be the case. All of the putting back in the
world, say in the form of human manure, will never, in itself, lead to
sustainability because so much more is lost than just what is being removed
by cropping. It’s doubtful that even the best no-tillage soil management
practice can prevent all these losses, but no-tillage can go a long way
toward closing this gap.

We also need to note that the carbon lost from the soil after plowing, in
the form of carbon dioxide, is lost to the atmosphere. There it contributes
to the rise of CO2 levels and consequential global warming. The amount of
CO2 added to the atmosphere is comparable, I have heard, with the amount
added by the burning of fossil fuels. One of the ways proposed for reducing
it is to sequester it back into the soil’s organic matter--presumably, in
part, by no-tillage practices. Here is a good opportunity for a whole
systems farmer to do her part to combat global warming.

Dr, Logan Carter founded the Soil Science Department at the California
Polytechnic College at San Luis Obispo. One of my memorable experiences
there was the shock I experienced when he announced to the class that
“tillage destroys soil structure”. He went on to explain some of the
other problems associated with tillage, after which I could hardly believe
that so much time, money and effort was put into tillage. Dr. Carter was a
man ahead of his time because this was still three or four years before the
first no-tillage plantings started going in; the early 1960s. To this day,
in the San Joaquin Valley of California, there still may not be a single
large scale, no-tillage planting. Old paradigms die slowly. It took me a
long time to “get it” myself.

“Structure” refers to the pore space and openness of soil to
penetration by air, water and roots. Indeed, tillage opens soil initially,
but more particularly, if tilth is fine that openness is lost at the first
good downpour or irrigation. It then closes much tighter than soil that has
been left undisturbed and makes a much less favorable environment for soil
organisms and roots.






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