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.
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.
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.
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...
"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...
Looking forward to hearing your thoughts...
Joel Gruver
Soil Quality Research
U of Maryland
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