Effective Microorganisms: What Happens When Soil Breathes Again

A small idea with a large consequence

In the 1980s, the Japanese microbiologist Teruo Higa developed a mixture of three groups of microorganisms that already coexist in nature: lactic acid bacteria, yeasts and photosynthetic bacteria. What sounds like yoghurt is actually biological precision: this community can reverse decay processes and turn them into build-up processes.

Higa called his mixture “Effective Microorganisms”, short EM. The idea spread from Japan across Asia and into Europe. Today, organic farmers, biodynamic farms, discerning plant enthusiasts and municipalities use it to revive soils, accelerate composts, resolve odour problems.

How do effective microorganisms (EM) work in soil?

In a conventionally treated soil, decay bacteria often dominate. They break down organic matter into stinking, unstable substances. EM reverses this direction: lactic acid bacteria lower the pH, yeasts produce enzymes and bioactive compounds, photosynthetic bacteria convert metabolic products directly into plant-available substances.

The result: the soil becomes calm, clear, slightly sweet-smelling. Odour disappears. Plants respond with stronger growth and higher resilience. On a rooftop terrace with limited substrate volume, this is clearly measurable – not in weeks, but in days.

What we use it for

We deploy EM in three applications:

1. Substrate activation for new plantings

Before placing plants, we mix the substrate with diluted EM. It activates soil life before the plant roots arrive and combines well with the fungal partnerships we inoculate in parallel.

2. Maintenance care for exclusive greenings

Under maintenance contracts, EM is used seasonally – usually in spring and late summer. A watering with diluted EM solution offsets a soil rest pause, amplifies the effects of compost layers and stabilises the soil environment after stress phases such as heatwaves.

3. Remediation of inherited greenings

When we take over existing greenings from other providers, we often work with significantly stressed substrates. EM in combination with organic substrates and fungal inoculation is the most effective approach here to recover a living soil environment within three to six months.

What EM is not

A miracle product. A fertiliser. A substitute for good substrate choice. Anyone watering EM solution onto exhausted soil and changing nothing else will see little. EM works in concert: living substrate, compost, fungal partnerships, organic care, soil rest. That is the methodology in which EM becomes a tool – and not magic.

EM is also not a substitute for scientific substrate planning. The right mix of mineral and organic components, matched to microclimate and plant species, remains the foundation. EM comes on top.

What you can do yourself

If you maintain an existing greening and want to use EM:

1. Mind the dilution. Common ratios are 1:100 to 1:1000, depending on application. Higher concentrations are not better.
2. Regularly, not once. A watering in spring and one in late summer works more than sporadic application.
3. Combine with compost. EM without organic material starves, because the microorganisms need nutrition.
4. Spray when mulching. Fresh mulch combined with EM spray decomposes calmly instead of turning anaerobic.
5. Check your source. There are reputable European producers with traceable ingredients. Look for transparent composition and organic certifications.

EM does not belong in every greening. But wherever the ambition goes beyond mere optics – wherever plants are meant to live long-term, not merely decorate – these invisible helpers are a tool that makes the difference.