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Re: Till/noTill (was Composted cow manure/rice nutrient cycles)



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