Getting started with effective microorganisms (EM): the 7 golden rules for success

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Effective microorganisms (EM) are easy to use, but they are living organisms: chlorinated water, a poorly rinsed sprayer or a container left out in full sun is enough to weaken them. Most disappointments come from these small mistakes, far more than from the product itself.

Here are the golden rules we recommend before you use them for the first time, in the garden as well as in the home. They apply to EM-1, Microferm and most of the liquid products in the range; for precise doses, your product's label is always the reference.

1. Use non-chlorinated water

The chlorine in tap water is there to keep microbes in check: it does the same to the microorganisms in EM. Manufacturers list it among the incompatibilities, and our own activator recipe points it out too: chlorinated water can prevent fermentation.

• Rainwater is ideal, provided it is clean and stored away from light.
• Tap water is fine if left to stand for 24 hours in an open container: the chlorine, being volatile, evaporates. The larger the surface, the faster this happens.
• Water filtered through activated carbon is also suitable.

Some water networks disinfect water with chloramines, which are more stable and do not evaporate. If in doubt, check with your water supplier or use rainwater. Use lukewarm rather than cold water for activation, never hot water.

Emy's tip

Always keep an open watering can or container filled with tap water next to your EM products: on the day you need it, your water will already have stood.

2. Never mix with bleach, disinfectants or fungicides

The technical data sheets are clear: bleach, chlorinated water, bactericides, fungicides and oxidising products reduce the survival of the microorganisms. Mixing the two means one cancels out the other.

• Never pour an EM product into the same tank as a chemical treatment product.
• Keep a sprayer just for EM, or rinse it thoroughly with clean water before use.
• After cleaning with bleach, rinse the surface and let it dry before using an EM cleaner.

Choose food-grade plastic or glass containers: EM solutions are acidic and can corrode some metals.

3. Dilute correctly

An EM solution is very acidic, with a pH of around 3.5. Undiluted, it can damage roots and foliage. It is almost always diluted. Here are the most common guidelines, based on the manufacturers' instructions:

• Watering soil and plants: 1% for Microferm, i.e. 10 ml per litre or 100 ml in a 10-litre watering can.
• Seedlings and young plants: more diluted, around 1:500, i.e. 2 ml per litre.
• Bedding, hen houses, kennels: 10 ml per litre of water as a spray.
• Cleaning with EM Clean: from 1 to 10% depending on the surface.

These figures vary from one manufacturer to another: for watering, you will find dilutions ranging from 1:100 to 1:1000. Always follow the one for your product, and prepare your mixture just before using it.

Did you know?

A "1:100" dilution means one part of product to one hundred parts of water. An easy way to remember it: 1:100 is a 10 ml capful in one litre of water; 1:500 is the same capful in five litres.

4. Prefer small, repeated doses

Professor Teruo Higa recommended several small applications rather than one large one, and the instructions follow this principle: increase the frequency rather than the dose. This advice comes from the manufacturer and has not been compared in independent trials, but it makes sense: overdosing wastes product and increases acidity, with no proven benefit.

In practice, it is better to water the vegetable garden every two weeks at the right dilution than to pour on a litre of almost neat product in one go. In the garden, apply preferably in overcast or damp weather, in the morning or evening, as the microorganisms do not cope well with full sun and drought.

5. Store somewhere cool, away from light and frost

• EM-1 keeps between 3 and 38 °C, ideally at a stable room temperature, in a dark place, with the cap closed. The date printed on our bottles is the use-by date (about two years after manufacture); other producers state about six months: follow the date on the label. It must never freeze.
• Microferm in Bag-in-Box keeps until the use-by date printed on the packaging (about one year after production), as the pouch does not let air in.
• A home-activated solution should be used within 1 to 2 months of being prepared.

A slightly swollen bottle or a whitish film on the surface is normal: it is a living culture. A distinctly putrid smell, on the other hand, indicates a failed product. We describe these signs in detail in the guide storing your EM and diagnosing a failed EM-A. Keep your products out of the reach of children and avoid contact with the eyes; in case of splashes, rinse with clean water.

6. Be patient and compare with a control area

Some effects show quickly, such as a reduction in litter odour. Others, in the garden, are slow and subtle, and published studies show that they do not always materialise. The best way to find out whether EM brings you anything is to run your own trial:

1. Choose two similar beds or rows (same soil, same aspect, same plants).
2. Treat one with EM and water the other with the same amount of water, without EM.
3. Note the dates, take photos, and compare what matters to you: germination, vigour, harvest.
4. Repeat for a second season before drawing conclusions.

Key points

A control area is worth more than any testimonial: it is the only honest way to find out what EM changes for you, in your soil and with your practices.

To find out what trials carried out elsewhere have shown, see our guide what science says about EM.

7. The most common mistakes

• Using tap water straight away, without letting it stand.
• Spraying an undiluted activated solution on leaves or seedlings.
• Storing the container in a car, a greenhouse or an uninsulated shed, where it gets hot in summer and freezes in winter.
• Reactivating an already activated solution to make more indefinitely: the manufacturer provides for only one activation, and nothing guarantees the balance of the mixture in subsequent generations. Start again from the mother solution, as explained in our guide activating EM-1 step by step.
• Expecting EM to make up for poor soil: it complements organic matter, it does not replace it. In the vegetable garden, it is used with compost, mulch or bokashi (see EM in the vegetable garden).
• Using a product for something it was not intended for: a garden or household product should never be used in the kitchen or in animals' drinking water without veterinary advice.
• Opening a bokashi bucket too often: each opening lets in air, the enemy of fermentation.

To get started without any preparation, Microferm EM-A is the simplest option for the garden, and EM Clean for the home. If you are unsure which product to choose, our guide choosing the right EM product will help you.

In summary

To succeed with EM: non-chlorinated water, never any mixing with bleach or treatment products, a dilution in line with the label, small repeated doses rather than one large one, and storage somewhere cool, away from light and frost. Finally, compare with a control area to judge for yourself. These simple steps prevent the vast majority of failures and help you get the best out of your products.

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Other topics in the guide

Vermicomposting30 sheets →Composting25 sheets →Bokashi24 sheets →