Sounds like you've really been thinking about this.
joel b gruver wrote:
> Hello to all...
>
> Early in the sawdust discussion, someone posted some comments about
> plants having different preferences with regard to soil
> bacteria and fungi...and refered us to Dr. Elaine Inghams
> (Oregon State) home page.
That was me.
> The basic idea was that certain crop species like Brassicas prefer
> bacteria dominated soils while others like strawberries prefer fungally
> dominated soils. In a recent article in "Worm Digest", I read that Ingham
> suggests that organic inputs (e.g. hot compost vs. cool compost, green
> manure vs. sawdust...) and tillage intensity can be used to
> specifically manipulate the microbial demographics of one's soil to match
> the preferences of an incipient crop.
>
As I said earlier, bacteria or fungus dominated compost (piles, mulch or green
manure) affect the life in the soil- through inoculation and providing the
food preferences.
> I am wondering about the anecdotal and scientific basis for this type of
> strategy for soil management... We know that some crop species are
> mycorrhizal hosts while others are not... there is certainly
> evidence that crop rotation into a non-host crop like canola
> will tend to reduce levels of mycorrhizal innoculum... but will canola
> perform best if the soil has been managed prior to planting for bacterial
> dominance. List member Steve Groff grows beautiful no-till brocolli... I
> would certainly guess that his no-till soils covered with rolled cover
> crop residue are fungally dominated.
>
The Brassicas grow best in a fungally dominated soil. (My lumping of
vegetables into a broad category was a mistake on my part- there are
exceptions in everything.) It sounds like Steve has found the best way to grow
broccoli through his experience. The information about how to manage soil life
for more vigorous plants gives us the opportunity to skip years of trial and
error and become more successful faster.
> Does anyone care to postulate any mechanisms by which one microbial
> demography would be prefered by a crop species over another ? Obviously
> microbial pathogens and specific symbionts have dramatic effects on crop
> performance but is there really evidence to support other generalizations
> ? The use of salt fertilizers, lime, cover crops, manure, compost or
> tillage... to promote crop growth will certainly also impact soil
> microbial ecology but should we tailoring our soil management to
> specifically manipulate microbial ecology...
The work done at Oregon State is not based on generalizations- I am the
generalizer. Check with Dr. Ingham for specific scientific references- there's
a list on her Soil Foodweb web site:
http://www.soilfoodweb.com/thesfw.html
Management practices do have a direct effect on the soil ecology. Tillage, for
example, breaks up the hyphae of the fungi and lowers the amount of fungal
life in the soil. So, tilling in a cover crop before planting would be
beneficial for corn (a grass) and limiting for broccoli. Dr. Ingham is
constantly reminding us that we need to look at the biological part of soil
and not just the chemistry. Each has an effect on the other.
>
>
> "Feed the soil not the crop" is a commonly stated organic tenet... are we
> now starting to understand a more intricate ecological basis
> for this concept or
> is Inghams work getting misinterpreted...
>
Exactamundo! This is why I'm so fascinated with the work of Dr. Ingham. After
30 years of organic growing and paying attention to the soil, it's exciting to
see someone starting to explain how what we've discovered from experience
really works. It's all about the soil life and there are scientists who are
looking at this- theoretically and in practical applications.
About her work being misinterpreted- please read her scientific publications
and bibliographies, not just short pieces from magazines. There has been a lot
of work done by microbiologists on soil ecology and soil life/plant life
relationships, both in the lab and in the fields.
Sadly, This kind of work is not being funded very well because it doesn't
include the eventual sale of product to farmers. If all you have to do is
change management to increase quality and productivity, there's no profit for
anyone but the farmer. We have gotten to the point where the type of
agriculture we practice is largely determined by ag. corporations. But that's
another story.
> Looking forward to hearing your thoughts...
>
And thanks for yours,
Alex
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