DEAR NEW FARM:
I understand mycorrhizae fungi are subject to pH but I have
not found an article saying what the parameters are.
We posed the question to Rodale Institute research agronomist
Dave Wilson. Here’s what Dave had to say.
We don’t have any specific pH parameters for mycorrhizae
fungi. This is what we do know:
In most well-aerated soils, fungi are the largest fraction
of microbial biomass. In general, soil fungi exist over
a wide pH range but are more tolerant of acid soils than
are other microorganisms. Consequently, to select fungi
instead of other microorganisms, people use a media that
has an acidic pH.
But, if the soil solution is too acidic, plants cannot
utilize N, P, K and other nutrients they need. The optimum
pH range for most crops is 6.0-7.5 and for leguminous and
other alkaline preferring crops, 6.5-8.0. Since the mycorrhizae
need to infect the root and carry on symbiosis with living
root material, it would stand to reason that the pH range
most optimum for any given crop is also the pH range most
optimum for the mycorrhizae types that infect that crop
and live in symbiosis with it.
Note: High rates of fertilizers, especially phosphorus,
inhibit the formation of mycorrhizae; organic forms of fertilizers
seem to have less inhibitory effect on mycorrhizae than
inorganic, soluble fertilizers.
As per our Fact sheet Improve
Your Soil, increase your Yields, and Reduce Your Expenses
with AM Fungi, we list the following steps to cultivate
your soil’s native AM fungus population.
- Don't fertilize with phosphorous. The benefits of mycorrhizae
are greatest when soil phosphorous levels are at or below
50 ppm. Mycorrhizal infection of roots declines above
this level with little if any infection occurring above
100 ppm P, even when soil is inoculated with a mycorrhizae
- Don't till more than necessary.
- Don't let fields lie fallow in winter.
- Do plant a cover crop.
- Do develop a diverse crop rotation.
- Do grow crops that support AM fungi.
us with comments, suggestions and questions.