Question
Asked 11th Jul, 2016

What are the optimal fungal to bacterial biomass ratios for different crops?

This is a question for soil microbiologists and ecologists.
Does anybody know about recent publications on the topic? The only publications I know of are those of Elaine Ingham and her colleagues. It is known that conifer forests are dominated by fungi whereas grasslands are dominated by bacteria and the structure of the soil foodweb (fungal or bacterial dominance) can influence the successional stages. However, as Ingham says  "More work is needed to establish what the optimal fungal biomass value should be for each type of crop, soil, organic matter, climate, etc." (http://www.rain.org/~sals/ingham.html  )
Soil Microbiology, Soil Fertility

Most recent answer

5th Feb, 2020
Anoop Kumar Srivastava
ICAR-Central Citrus Research Institute ( Formerly National Research Centre for Citrus)
In our studies in fruit crops , bacterial population we find , much higher than fungal population in any healthy orchrd....what happens in replant disease issue..??

Popular Answers (1)

Deleted profile
Dear  Christopher-Joseph
As observed and reported in old soil microbiology publications, It is all a matter of soil pH, and competition.
1-  In general bacteria are more competitive than fungi when it comes to rapidity for use of nutrients rich in energy.
2- Bacteria in general prefer a pH near neutrality. Most fungi also, but they can also proliferate when pH tend to be acid.
So when soil pH is acid, fungi are more abundant than bacteria. (most of which have an optimum pH for growth near neutrality) and because of these observations some people think that the fungi have an acid optimum pH, which with a few exceptions is not right.
When soil pH is near neutrality, bacteria proliferate because they are more competitive than fungi.
Now, how about mycorrhiza? They are fungi and very abundant in soil, but they do not compete with bacteria for nutrients since they form an association with plant.
We also know that they harbor bacteria in their hyphosphere and these bacteria are fed by photosyntate from the plant released via the mycorrhizal hyphal network.
So may be we should forget about calculating an optimal ratio and look at soil biological communities as a whole system.
Kind regards
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All Answers (7)

12th Jul, 2016
Anoop Kumar Srivastava
ICAR-Central Citrus Research Institute ( Formerly National Research Centre for Citrus)
Very interesting question posted Christopher-Joseph . i dont think , we have yet quantified the optimum load of soil  bacteria and fungi in relation to production levels or any other soil parameters..?
Fungal:bacterial dominance of growth, biomass, and residue indicate different, and not directly relatable aspects, of the microbial community’s influence on soil functioning. Considering relationships to environmental factors, we found that shifts in fungal:bacterial dominance were not always in line with the general expectation, in many instances even being opposite to them. This is likely because the traits expected to differentiate bacteria from fungi are often not distinct. Considering the
impact of fungal:bacterial dominance on ecosystem function, we similarly found that expectations were not always upheld and this too could be due to trait overlap between these two groups ( Source :  Strickland and Rousk 2010, Soil Biology and Biochemistry, 42: 1385-1395) . Find one interesting PDf relating this issue. 
2 Recommendations
Deleted profile
Dear  Christopher-Joseph
As observed and reported in old soil microbiology publications, It is all a matter of soil pH, and competition.
1-  In general bacteria are more competitive than fungi when it comes to rapidity for use of nutrients rich in energy.
2- Bacteria in general prefer a pH near neutrality. Most fungi also, but they can also proliferate when pH tend to be acid.
So when soil pH is acid, fungi are more abundant than bacteria. (most of which have an optimum pH for growth near neutrality) and because of these observations some people think that the fungi have an acid optimum pH, which with a few exceptions is not right.
When soil pH is near neutrality, bacteria proliferate because they are more competitive than fungi.
Now, how about mycorrhiza? They are fungi and very abundant in soil, but they do not compete with bacteria for nutrients since they form an association with plant.
We also know that they harbor bacteria in their hyphosphere and these bacteria are fed by photosyntate from the plant released via the mycorrhizal hyphal network.
So may be we should forget about calculating an optimal ratio and look at soil biological communities as a whole system.
Kind regards
5 Recommendations
14th Jul, 2016
Annangi Subba Rao
Indian Institute of Soil Science
Dr.Antoun,well explained and I endorse the comments.
1 Recommendation
14th Jul, 2016
Ewald Schnug
Chinese Academy of Sciences
because of the many and different factors involved for both species, there simply can not be an "optimum" ration!
5th Feb, 2020
J.E. Van der Waals
University of Pretoria
Is it optimal to have a higher fungal : bacterial ratio in soil, or vice versa (for healthy soil)?

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