[John]

Hopefully you can help. Does anyone know of proper trials on the efficacy of aerated compost tea. I can find people raving about it but unless they have comparison controls it's just guesswork.

I did come across one small trial where the results were no benefit whatsoever.

It strikes me it may be a bit like rockdust - lots of individuals claiming it's wonderful but all the properly run trials (paid for by the Scottish Gov.) bar one failed to show any benefit. The one success was pretty marginal.

[solway cropper]

I tend to agree that the evidence for the supposed benefits of aerated compost tea is underwhelming. Over the years I've seen so many fads and trends, all of which are supposed to improve this or help that and most of which require the gardener to purchase something. In short, the only ones getting any benefit are the ones selling the idea. If you use healthy seed and healthy plants in healthy, fertile soil then little else should be required. It's a bit like the giant con of persuading people that their guts require the addition of 'beneficial bacteria' in the form of fancy yogurts in order to function properly.

[John]

So far I've found some academic papers showing some minor benefits to a very limited range of plants from some compost teas.

So my conclusion is that making aerated compost tea by adding some compost & molasses to water then bubbling it for 48 hours will make a liquid rich in bacteria.

Depending on what went into the compost, the mix of bacteria in the tea will differ. Probably from batch to batch even made from the same compost base.

If you have the 'right' mix of bacteria then it may help some plants. An awful lot of variables...

I may start a business selling compost tea.. I also have some magic beans for sale

[jambop]

There are a great many products that are sold on the same basis. One example that I have a gripe with is shotgun cartridges. I have not seen one study on any cartridge by any manufacture that proves their product. The simply give them free to an expert shooter to use and his results then sell them. I have heard individuals of lesser expertise swear they shoot better with brand X ... it is all in the head if the cartridges were not marked in anyway they would be literally shooting in the dark as to cartridge efficacy that is not to say that some cartridges have better aspects to them than others... but can you break more targets with them ... I doubt it.

[JayG]

Bit like 'superfoods' for humans - although it's a tempting concept (especially for the producers ), plants are also complex organisms with different requirements for optimum health and growth - one size has never fitted all and never will. 

[John]

jambop - what's your point? If you think my conclusion wrong regarding compost tea, please explain why.

[jambop]

jambop - what's your point? If you think my conclusion wrong regarding compost tea, please explain why.

No John Far from it you are absolutely correct unless a proper trial has been carried out people just tend to  "think" that this or that is better... without actually looking at the cold hard facts of a properly conducted test. I worked in a area that relied on proper testing to be able to sell any new product that was developed if the company could not prove in a valid test that what was being proposed actually did work then quite literally billions of pounds worth of research was wasted. the pharma industry is a very costly business research wise. I think you have just misinterpreted what I said re cartridges companies make them and give them to expert shots to get results in competitions ... they are then sold on the hearsay of how good they are however these expert shots could shoot just as well with just about any cartridges.  The same happens with other products Fred tries it he thinks it works and tells Bill who tries it and thinks the same... etc ... but they never do the tests under the same conditions it is therefore inevitable that some of the results will be skued one way or another... a properly thought out test is the only way to prove something does something.

[John]

Hi Jambop - thanks for explaining. I was genuinely confused as to your meaning, probably as I didn't get much sleep last night.

There's a lot of sites and youtube videos claiming miraculous results for compost tea but precious few comparison trials. Sadly (for me) the academic papers are really hard work to puzzle out being as they're aimed at a scientific audience who know the jargon etc.

I'm very much in favour of organic growing and biological controls. Promoting solutions with no basis in fact doesn't help that cause. Like Solway Cropper, I've seen many fads, fancies and miracle solutions come and go. Some seem to crop up again though.

[Salmo]

If you soak compost the liquid that comes off must contain more nutrients than tap water. I have no doubt that aerating it multiplies the bacteria but of course there is no guarantee that these are good or bad for plants or soil. The nutrients are only of benefit if the crop needs them.

Here is a useful YouTube clip. This guy really knows his stuff.

https://www.youtube.com/watch?v=UmPfQBSw9cA

[John]

Oh Salmo, that's exactly what I mean. Singing the praises of compost tea but no evidence that the tea is giving him good results or something else.

I did note he adds chicken manure to his initial compost mix. Could that contain salmonella or e-coli? Especially on a crop that may be eaten. Just because it's 'natural' doesn't guarantee it's safe. And finally, we're not promoting activities such as growing marijuana on here, thank you. It is illegal in the UK 

[victoria park]

It all sounds like the latest fad with must have books and more essential products to buy at the end of it. It also seems rather more complicated than it need be for the assumed minimal benefit.
Over the years, my method has had much of organic practice, permaculture, no dig, sustainable philosophy, low air miles/oil products, whatever,  at it's core. Not 100%, but pretty close. The methodology doesn't need to sell products, it needs to convince people of sustainable natural methods with simple ingredients available for free on our plots, and few commercial interests at it's core. And keep away from the scientific jargon which is the sort of thing Bayer, Doff etc use, be it true or not.
Having said that,     manufactured organic chicken manure pellets were sent by the gods to us small growers. I can't keep hens, and worry about current manure aminopyralid problems, so I allow myself to import the pellets onto the plot, 15, maybe 20kg a year. I also get a fair old supply of free woodchip from local tree surgeons, and a bit of winter storm seaweed, so that helps to.

[jambop]

The problem with testing a product such as this in a garden situation is the physical conditions ... they are going to be different from one location to another. So you need to conduct the experiment on the same site and study the results... but that only means that in the growing conditions at that one site the product achieved a certain result which could be entirely different at another site with different conditions. In short just because it may work in one set of conditions it may not in a different set. However if somebody who takes the time to do this thinks it works for them then why not do it... just do not promote the product as a universal solution to feeding plants. One thing that I think could be a problem is over watering plants in an effort to feed them... why not just let them have the compost and let the rain and occasional watering leach the nutrients to the plant roots ?

[New shoot]

Didn't the rock dust craze start when some people used it to create soil to grow in, where they had nothing previously.  It has shown benefits in some parts of the world, where the soil is almost devoid of rock debris, but UK soils are full of natural rock dust, having had several ice ages pulvervising the terrain in its history.

If your soil is particularly sterile and lifeless, I've no doubt compost tea would benefit it.  I make and use a lot of compost and my soil is full of earthworms and other soil creatures.  I've no idea how much bacteria is in there, but as the higher life forms are numerous, I assume I have a goodly amount.

I may start a business selling compost tea.. I also have some magic beans for sale

It may be a tough sell on the compost teas, especially if they contain fermented chicken manure pellets    Imagine the smell    Now about these magic beans ...
 

[Dr_Pepper]

Hi John,

The link below should take you to a page where you can download the reports out of a project I was involved with several years ago with Cranfield University. The basic headline is that in well-managed soil-grown horticultural crops where regular inputs of organic matter are part of the crop management programme, compost teas, or off-the-shelf microbial preparations have little effect.

https://horticulture.ahdb.org.uk/project/improvement-soil-health-manipulation-microbial-community-characteristics-0

It's a masters student's project so it gets quite scientific as you read but the top 'Grower section' should be quite readable for all.

Neal

[John]

Thanks for that, Neal

It's sad really, there are so many people promoting the concept which on first glance makes you think it must be a good idea but when you think it through further the theory gets shaky and it seems there is no properly researched evidence it works to speak of.

I tend to be very sceptical about these 'fads' but I always hope to proven wrong.