Happy Spring Equinox!
I know, it's been an on-again, off-again roller coaster ride here in Victoria, with all that snow just a month ago and temperatures still hovering in the single digits. But the birds and flowers are now out in force and they can't be wrong, can they?
Recently the Gaia College discussion forum saw an excellent exchange on similarities and differences between microbial inoculants, namely Compost Tea and Effective Microorganisms. I wrote a summary of the salient points and I thought you might like to know this too. So here it is - enjoy!
In a nutshell, both Actively Aerated Compost Tea (AACT) and Activated EM (AEM) have similar benefits in the garden. Both have been shown to suppress pests and disease (and I say this while keeping in mind that what is commonly called a pest or disease organism must really be seen as a plant predator, and therefore a messenger indicating some underlying problem, which in turn has almost always to do with the plant's nutrition).
Both AACT and EM are best used as a preventative measure rather than to "treat" a fully developed "disease".
AACT has been shown to increase Brix levels (sugar content) in plants, and the protein content in forage grasses. Indirectly, and over time, it will help relieving compaction, forming good soil structure, improving natural fertility, and reducing the needs for watering and fertilizing and, uhm, pesticides. No need to elaborate on that...!
AEM is a good choice to aid organic matter breakdown, and generally for outcompeting pathogens. AEM has a much broader range of applications than compost tea; they include water and waste water treatment, manure management, odour reduction, all kinds of cleaning purposes, cosmetics and body care, human food and animal feed additives, and making bokashi, to name just the most common.
AEM is made from lab-produced mother culture using a prescribed, proven recipe (and for consistent quality it is important to use fresh mother culture for each activation batch), and the species and numbers present are somewhat predictable.
AACT on the other hand can have a wide range of organisms depending on what the compost consists of; in addition, composts can be custom made to be more bacterial or more fungal dominated, and can further be pre-treated before brewing; and then there is the option to add selective microbe foods to the brew too. In other words, lots more room to "play" with AACT and customize it; potentially lots more biodiversity, but also less predictability.
As a side note, good compost tea contains fungal hyphae, but does not contain mycorrhizal fungi, as those need a living host plant and cannot be extracted or propagated in compost tea. AEM does not contain either.
When it comes to cold temperatures (and I had quite a few customers ordering microbes this winter and wondering how they would fare in transit, and with cold weather), there is generally little point in applying AACT or AEM to frozen ground, or on top of snow cover. That said, the microbes are surprisingly cold hardy and will even endure short periods of light freezing by going dormant. Only if exposed to frost for about a week or more will populations start to die off, according to technical info from one EM supplier.
Both AACT and AEM are synergistic brews and part of their effectiveness is based on the organisms forming mutually beneficial relationships amongst each other and with the outside world's microbes.
As a final note, neither Actively Aerated Compost Tea nor Activated EM is a silver bullet and *always* must be used as part of a comprehensive soil organic matter management program.
Feel free to contact me with any questions or comments you may have!
Also, watch the pantry web site for some upcoming name changes and product updates.
I'll be happy to help with all your organic gardening needs as always!
See you out in the garden.