Re: Till/noTill

From: Elaine Ingham (Soilfoodweb@AOL.COM)
Date: Wed Apr 09 2003 - 19:45:04 EDT


The intensity of any disturbance is something you have to consider in order
to determine the degree of damage to the fungi, the protozoa, the nematodes
and the microarthropod communities, and the degree to which bacterial growth
will be enhanced.

The greater the intensity of disturbance, the more marked these changes. So,
a single time through the soil with a moldboard plow will result in a barely
observable effect on the fungi or the bacteria.

A chisel plow will cause a greater response, because the disturbance is much
greater. A roto-tiller will result in quite a bit of disturbance, and it's
effect is much greater, and more easily detected.

If the soil is not compacted, there is no anaerobic layer deeper in the soil.
 Read the work from Duke University about the miocrobial populations with
depth into the soil. There was plenty of oxygen down even as deep as 6 feet.
 Read the work by researchers at Colorado State University, where grass roots
went down to 12 to 15 feet or more, and the soil was fully aerobic at that
depth.

People have a very warped understanding of aerobic and anaerobic zones in
soil, because of the artefact imposed by the disturbance that people impose
on soils. Compaction, whether caused by large numbers of people or cattle or
horses, or herds of buffalo walking on the soil, or by plowing the soil and
imposing hard-pans, or by floods, or other disturbances, prevents oxygen from
diffusing into the soil. Once the soil food web is returned to that soil,
and soil structure is re-built, the air passageways are re-formed, and oxygen
again moves into the soil, perhaps as far down as 12 miles. We find aerobic,
active organisms in soil as far down as 12 miles. Check out some of the work
by David Balkwill.

"Bad" is a relative thing. If you need the soil to be bacterial, to grow
early successional plant species, then maintaining the soil in that early
successional condition will not be a bad thing. But if you don't want weeds,
if you are trying to grow trees, then killing the fungi by slicing and dicing
with a plow, is not a good thing.

It all depends on your objectives.

If your sole objective is to turn weeds under, then plow to your hearts
content. But you will also compact the soil, you will kill fungi, you will
increase bacterial dominance, likely increase erosion, and reduce your
ability to hold calcium, and other nutrients. Is this what you mean to do?

If your regular cover crop competes with your vegetables, maybe you have
chosen the wrong cover crop.

Do freeze/thaw events, or earthworms, inflict the same degree of disturbance
as a single plowing event? If the bacteria and fungi are asleep, as they are
in cold soil, the impact of a freeze or thaw will be minimal. You will get
mixing of the soil surface, but not much impact on the living organisms.

Earthworms mix soil as well, but they actually help soil structure improve,
because they build bacterial, fungi, protozoan and beneficial nematode
biomass and activity in the soil. They increase the ability of air to
diffuse into soil. They leave behind them greatly altered microbial
communities, usually ones that are very beneficial to the growth of healthy
roots. Please read the work by Dr. Clive Edwards, Ohio State Univ.

How do you cut your weed cycle without tilling? By improving soil chemistry
and soil biology. Set the conditions in your soil to select against the
growth of the weeds. You have to learn what the weeds are telling you about
conditions in your soil. Thistle tells you that you have much too high
nitrate levels. Disturbed soil often have highly un-balanced nutrient
cycling, because the fungal to bacterial ratio is hugely out-of-balance, and
nitrate pulses occur. So thistle wins in competition with other plants.

Moss tells you that the soil lacks plant available iron. A standard soil
chemistry may say your soil has fine levels of iron, but do a test for plant
available iron, and you discover that the iron is all reduced, and completely
plant not-available. How do you get that not-plant-available reduced iron
back into a plant-available form? Not by plowing the soil.

You asked -
> But maybe I'm missing something huge here - by my first question to your
> post was, how much can you really chop and dice microscopic fungi and
> bacteria???

The best way to know if you are decreasing fungi and/or bacteria by any
disturbance that occurs or is imposed by a human is to do direct counts of
the bacteria and fungi in the soil. Also do an assessment of ACTIVE bacteria
and fungi. Prove to yourself the effects that using a moldboard, a disk, or
a rotary plow have on soil life.

Elaine Ingham
President, Soil Foodweb Inc.
www.soilfoodweb.com
SFI Oregon, USA
SFI Australia
SFI New York
SFI Europe
SFI New Zealand

"Hope is not a feeling. It is not the belief that things will turn out well,
but the conviction that what we are doing makes sense, no matter how things
turn out." -- Vaclav Havel, former President of the Czech Republic






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