Is peat anti-microbial?

[burningtree]

Local organic gardening guru Howard Garret suggests that peat is anti-microbial and therefore works at cross purposes with the organic grower. Any thoughts on the matter?

 

[mad librettist]

My sundews can't be given tap water. Not because of chlorine, or because anything in there is toxic to these sensitive plants, but apparently because the minerals in tapwater allow the microbes in the peat to thrive, releasing some N, which kills the plant unless you repot it with bare roots.

So I have trouble buying that peat is anti-microbial, since my medium for the sundews is 50/50 peat and perlite. Maybe it favors one type of microbe over another, but that's it.

 

[ColBatGuano]

Peat is anti-microbial, but having anti-microbial properties is not necessarily a bad thing, even in organic growing. From what I understand, aerobic microbes, especially fungi, love peat.

 

[burningtree]

Thanks M L and Col. for the input.

 

[VerdantGreen]

i hope MM doesnt mind me reproducing this from another peat thread.

I've never used coco but logic prevaling it is not likely that a coconut product would contain humus and plant/soil based microbes that are normally contained in peat moss. Besides the potential unsustainability issue around peat harvesting, personally I would lean towards it because of the disease preventing microbial make up and the sequestered nutrient value in its humus component. Here is an interesting albeit commercial link;
http://www.peatmoss.com/hortprog1.php
Please note that reports stating that peat moss is an inert medium are unsubstantiated. It is loaded with microbial life as illustrated here; http://www.microbeorganics.com/#Canadian_Sphagnum_Peat

http://www.icmag.com/ic/showthread.php?t=154459

 

[secondtry]

Canadian peat IS NOT antimicrobial and The Dirt Doctor is being lame on this topic, he just won't accept fact and stop spreading lies...

He has been told over and over again by people like myself and others he is wrong, yet he won't accept that. I believe I have given him, or one of his associates this study a while back when there was a dust up somewhere else on this very topic.

Carlie, et al.
“Microbial Activity in Growing Media – A Brief Review”

Abstract:
Many investigations have been conducted into the activities of microorganisms during processes of composting of substrate constituents such as bark, animal and plant wastes, as well as domestic refuse. Much less is known of microbial activity within soil-less media prepared from these and other substrates. The microbial flora of substrates prepared from composted materials may be rich and diverse, whereas that of native peats may be low and microorganisms may be absent initially from materials such as perlite, vermiculite and mineral wool.

After wetting, fertilisation and in the case of peats, pH adjustment, soil-less media become amenable habitats for the development of microbial populations. Microbial pathogens of media, such as species of Pythium and Phytophthora, as well as some Fusarium wilts may still pose considerable problems in soil-less media. The saprophytic microflora of growing media, though, is much less well researched. Investigations of the saprophytic microflora have largely involved determination of the products of microbial activity, such as nitrate in nitrification processes. However, measurement of respiratory activity, ATP changes as well as direct counting and planting techniques have been used to monitor microbial activity.



The low initial population of microorganisms in certain media - notably these containing peat and inorganic constituents such as perlite and mineral wool - may allow establishment of artifically introduced microorganisms. Introduction of antagonistic fungi such as Trichoderma may confer control of certain pathogens, as well as enhancing growth of plants in media. Certain rhizobacteria may exert similar effects. Reductions in the activity of pathogenic microorganisms may further be achieved by use of media constituents, such as some types of bark, which may have suppressive effects on these microorganisms. This manipulation of microbial growth in soil-less media may offer considerable benefits to growers, and may form an integral part of commercial use of soil-less media in the not too distant future.

 

[mad librettist]

Thanks 2nd try, that's that's a nice din you are making. Explains why I have to be so careful with my drosera.

 

[burningtree]

The link from Verdant green and the abstract from 2ndtry seal the deal for me. Thanks everyone. I'm enjoying the community. Take care.

 

[guest2012y]

Has anyone here ever left an open bag out in the weather and forgot about it,then went to open it up a great while later and get that rotten smell? Peat definitely supports/propagates microbial life good and bad. Just throwing that in the thread as a less scientific observation based on my own discovery of rotting peat.

 

[BurnOne]

I've been growing in it for years. Never seemed to harm the microbes in my mix.
Burn1

 

[ColBatGuano]

Studies on the Pharmacologic and Biologic Activity of Peat
by Wollina, U. et al

In the past, crude extracts from peat of various sources have been screened for antibacterial activity. Humic acid and fulvic acid exert antimicrobial activities in vitro. Antibacterial activity has been shown against a variety of pathologic germs including Staphylococcus aureus, E. coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and against yeasts like Candida albicans. Humic acids and poly(OH)carboxylates are selective inhibitors of Herpes simplex virus and Cytomegalovirus replication. Oxihumate - a water-soluble compound of peat - inhibited HIV-1 infection of MT-2 cells with an IC(50) of 12.5 µg/ml. Treatment of free and cell-attached HIV with oxihumate irreversibly reduced infectivity, while the susceptibility of target cells to the virus was not impaired by treatment prior to infection. The infectivity of the HIV particles was inhibited by interference with CD4 binding and the V3 loop-mediated step of virus entry. No viral resistance to oxihumate developed over a 12-week period in vitro. Furthermore, it was shown in vivo that oral administration of humus extract in freshwater fish prevents infection with the fish pathogen Aeromonas salmonicida . The remnants of a biodiversity of plants are responsible for the broad-range antimicrobial activity found in peat.

I think this is part of the controversy. Folks like the "Dirt Doctor" read these sorts of studies and make connections/conclusions from them which aren't in the actual studies. The previously posted abstract discusses the introduction of microbes in soilless mixes containing peat, where the anti-microbial properties of peat illustrated in this study are from extractions taken from peat. There is a lot of information on the web about the anti-microbial properties of peat, and its use as a preservation medium. There is even the one about preserved fish which the "Dirt Doctor" mentions on his page. I think, at least from what I've been reading over the past day or so, that peat in its natural form, and extractions made from it, do have anti-microbial properties--but these are perhaps "diluted" when peat is used as part of a soilless mix. Besides, there is no mention of anti-microbial activity against the beneficial microbes required to feed plants.

 

[Microbeman]

Dr. Dirt is full of it!

Thanks Verdant. Just the facts only the facts please.

 

[Microbeman]

I think this is part of the controversy. Folks like the "Dirt Doctor" read these sorts of studies and make connections/conclusions from them which aren't in the actual studies. The previously posted abstract discusses the introduction of microbes in soilless mixes containing peat, where the anti-microbial properties of peat illustrated in this study are from extractions taken from peat. There is a lot of information on the web about the anti-microbial properties of peat, and its use as a preservation medium. There is even the one about preserved fish which the "Dirt Doctor" mentions on his page. I think, at least from what I've been reading over the past day or so, that peat in its natural form, and extractions made from it, do have anti-microbial properties--but these are perhaps "diluted" when peat is used as part of a soilless mix. Besides, there is no mention of anti-microbial activity against the beneficial microbes required to feed plants.

Having microbes which produce enzymes which prevent/suppress pathogens is different than 'being dead as cutters nuts' which words the Dr. Doctor uses to describe sphagnum peat moss. One only needs to look at the tests I ran with pure peat to refute this nonsense.

 

[ColBatGuano]

Having microbes which produce enzymes which prevent/suppress pathogens is different than 'being dead as cutters nuts' which words the Dr. Doctor uses to describe sphagnum peat moss. One only needs to look at the tests I ran with pure peat to refute this nonsense.

You said it better than me, Microbeman! I had never heard of the Dirt Quack until yesterday, and after going through some of the stuff on his site, I think you're probably right about him being FOS. (my words )