Soil biology · Guest feature
Activated EM-1 for crops and compost: what the research shows
A box of living microbes promises a great deal. Here is what peer-reviewed trials have measured, and how to get the most out of it.
Activated EM-1 is a fermented mixed culture of beneficial microbes, including lactic acid bacteria, yeasts and photosynthetic bacteria (Iriti et al. 2019). In peer-reviewed trials it has raised growth, yield and quality across a range of crops. In one greenhouse study, the authors report that it increased tomato plant growth by 35% and fruit production by 61% (Megali et al. 2014), and a meta-analysis of 39 studies found a positive effect on growth and yield (Megali et al. 2015). Added to compost, it raised the nitrogen, phosphorus and potassium in the finished heap (Jusoh et al. 2013).
On who is writing: I run Dr Forest, which makes handcrafted organic fertilisers, and we do not sell EM-1 or Actiferm, so take this as a look at the evidence, not a sales pitch. Several of the best results below came with EM working alongside organic matter: compost, bokashi and manure.
In short
Activated EM-1 is a live microbial culture. Peer-reviewed trials have measured gains in growth, yield and fruit quality, and in the nutrient content of compost. It works with organic matter rather than instead of it: in an 11-year wheat trial, the same compost gave better results once EM was added (Hu & Qi 2013).
What "activated" EM-1 actually is
EM-1 is the mother culture of Effective Microorganisms, developed in Japan by Dr Teruo Higa (Olle & Williams 2013). It is a fermented mixed culture of compatible microbes held in an acidic medium; the main groups include photosynthetic bacteria, lactic acid bacteria, yeasts and actinomycetes (Iriti et al. 2019).
Activated EM-1 is that culture woken up and multiplied into a ready-to-use working form. The simplest way to get it is Actiferm, which Agriton describes as a blend of activated effective micro-organisms: bacteria, yeasts and moulds. It comes in a bag-in-box with a tap, so you draw off what you need without letting air back into the bag. Agriton advises storing it somewhere cool and dark.
What the trials show on growth, yield and quality
The cleanest single result comes from a greenhouse tomato trial by Megali, Glauser and Rasmann. The authors report that the microbial mixture increased plant growth by 35% and fruit production by 61% (Megali et al. 2014). At Agriton's recommended dilution of 1:100, a 2-litre box makes 200 litres of spray.
Figure 1 · growth and yield response to EM
Reported gains in growth and yield
Increases reported with EM in three peer-reviewed studies, from greenhouse tomato to field vegetables. Figures as published by the authors.
One trial is one trial, so it helps that the same group followed it with a meta-analysis of 39 published studies and a greenhouse experiment across nine crops, among them tomato, lettuce, onion, carrot, spinach and peas (Megali et al. 2015). The pooled studies showed a positive effect of EM on growth and yield, and in the greenhouse EM increased plant growth by 16%.
A review of the vegetable research found the same direction of travel. In 70% of published studies, EM had a positive effect on vegetable growth, and of 22 reports on vegetable yield, 84% were positive (Olle & Williams 2013).
Quality moves with yield. In a tomato trial comparing organic and chemical fertilisers, inoculating EM onto bokashi and onto chicken manure increased leaf photosynthesis and fruit yield, and EM raised vitamin C in the fruit in every fertiliser treatment. Fruit from the bokashi-fed plants also had higher sugars and organic acids than any other treatment (Xu et al. 2001).
Lettuce tells a similar story. In a glasshouse trial, a soil-applied microbial culture plus three-quarters of the recommended chemical fertiliser gave the highest total yield in the trial, 6.7% more than the full chemical rate on its own; adding a leaf spray to the same regime gave 6.3% more. Marketable yield was statistically level across those treatments, so the gain is a quarter less chemical fertiliser for at least the same crop (Demir et al. 2024).
Beans and field vegetables point the same way. In a greenhouse pot trial, beans given a weekly soil drench of EM-1 held their peak leaf photosynthesis two weeks longer than untreated plants and gave more seed on every growing medium tested (Iriti et al. 2019). On commercial organic farms in New Zealand, EM applied with molasses raised onion yield by 29%, the share of top-grade onions by 76%, pea yield by 31% and sweetcorn cob weight by 23% (Daly & Stewart 1999).
Compost and bokashi: add EM while you make them
Adding EM to compost means inoculating the heap while you build it, so the microbes work on the raw material as it breaks down. You then spread the finished compost on your beds as normal. The lactic acid bacteria in EM can make the nutrients in compost and other organic material more available to plants (Lamont et al. 2017).
The trials show why it is worth doing. Rice straw composted with goat manure and green waste for 90 days finished with significantly more nitrogen, phosphorus and potassium when EM was added, along with more iron (Jusoh et al. 2013). A 2026 trial co-composting mushroom residue with chicken manure found that EM shortened the heating phase, lengthened the hot thermophilic stage and sped the breakdown of cellulose and hemicellulose; at the 10% inoculation rate the pile passed 50 °C by day 2 (Feng et al. 2026).
The benefit carries through to the crop. In an 11-year trial in China, wheat fed with EM compost gave significantly higher straw biomass, grain yield and grain nutrition than wheat fed compost made without EM, and the authors concluded that EM increased the efficiency of the organic nutrients (Hu & Qi 2013). Maize grown on the EM compost in the 2026 trial developed better roots and gave a higher yield (Feng et al. 2026). And in a tomato trial, EM inoculated onto bokashi and onto chicken manure raised leaf photosynthesis, fruit yield and fruit vitamin C (Xu et al. 2001).
How to make an EM compost heap
This is the method from the rice straw trial, which used activated EM-1 (Jusoh et al. 2013).
- Mix your materials The trial heap was, by weight, half rice straw, three-tenths goat manure and one-fifth green waste. The straw was shredded and soaked in water for 24 hours first (Jusoh et al. 2013). You do not need those exact ingredients; see the swaps below.
- Make up the EM solution The trial used a 5% solution of activated EM in water, which is 50 ml per litre. Agriton's general dilution for Actiferm is 1:100, which is 10 ml per litre.
- Wet the heap with it as you build The EM solution made up a fifth of the water added to the heap. Plain water was then added until the material reached about 60% moisture, and it was kept at 50 to 60% moisture throughout.
- Cover and turn The heaps were covered with plastic sheeting to hold in moisture and heat, and turned every three days.
- Give it time, then spread it The trial composted for 90 days, and the finished compost was mature and fit to use without restriction.
No rice straw or goat manure? Use what you have
The trial heap was simply a dry, carbon-rich material (the straw) mixed with manure and green waste. The RHS guidance on composting groups garden materials the same way, as "browns" and "greens":
- Instead of rice straw (browns) Any other straw, dead stems, shredded prunings and hedge trimmings, or torn-up paper and cardboard. These are the dry, carbon-rich materials the RHS lists as browns. Soak dry straw first, as the trial did.
- Instead of goat manure Chicken manure, which was the manure used in two of the other trials in this article (Feng et al. 2026; Xu et al. 2001), or any fresh manure you can get hold of.
- No manure at all Use more greens: grass clippings, annual weeds, crop waste, old fruit and vegetables and kitchen peelings, which the RHS lists as nitrogen-rich. Mix grass clippings well with browns, as on their own they turn slimy.
The RHS suggests a heap of roughly a quarter to a half greens, with browns making up the rest. Keep the EM solution, moisture, cover and turning the same as the method above.
In a bokashi bin
Bokashi works on the same principle in a sealed bin. In Agriton's words, EM added to the organic matter drives a fermentative breakdown that produces a pre-digested, nutrient-dense ferment for use as a soil improver or organic fertiliser; their bokashi guide covers the method. Agriton also lists Actiferm as a compost accelerator for fermenting vegetable and animal remains.
Why it works
Start with the lactic acid bacteria, the same group of microbes behind yoghurt. A review of their use in plant production found that, as biofertilisers, they can improve the availability of nutrients from compost and other organic material, and as biostimulants they can promote plant growth and help plants cope with abiotic stress (Lamont et al. 2017).
There is plant physiology on top of the soil biology. In beans grown on salty soil, EM improved growth and increased the uptake of nitrogen, phosphorus, potassium, calcium, magnesium, iron, zinc and copper, whilst cutting sodium uptake; it also improved the plants' water content and membrane stability (Talaat et al. 2015). A companion study found EM raised the plants' antioxidant enzymes further and reduced oxidative damage (Talaat 2015).
Put together, the trials show nutrients released from organic matter, leaves that keep photosynthesising for longer, and plants better able to cope with stress.
Lactic acid bacteria are old friends from the kitchen. The trick is giving them something to eat and somewhere to work.
When it works best
Organic matter is the common thread. The tomato gains in the Xu trial came with EM inoculated onto bokashi and manure (Xu et al. 2001), and in an 11-year wheat trial the same compost gave significantly higher straw biomass, grain yield and grain nutrition once EM was added (Hu & Qi 2013).
Plants under stress benefit too: on salty soil, EM improved bean growth and nutrient uptake (Talaat et al. 2015).
And the successful trials applied it regularly. The beans were drenched weekly through to the end of flowering (Iriti et al. 2019); the New Zealand onions had three applications and the sweetcorn seven (Daly & Stewart 1999); the wheat result came from eleven years of use (Hu & Qi 2013).
How to get the results
Five concrete moves, each tied to the evidence above.
- Put it with organic matter Apply it with or onto a mulch, a compost top-dressing or your bokashi. EM inoculated onto bokashi and manure raised tomato yield and fruit vitamin C (Xu et al. 2001), and EM made the same compost go further for wheat (Hu & Qi 2013). The New Zealand farm trials applied it with molasses (Daly & Stewart 1999).
- Add it to your compost heap or bokashi bin Inoculate the heap while you build it, using the method above, then spread the finished compost on your beds. EM compost carried more nitrogen, phosphorus and potassium (Jusoh et al. 2013) and grew more wheat and better grain than the same compost without EM (Hu & Qi 2013).
- Use it where plants are under stress In beans on salty soil, EM improved growth and the uptake of the major nutrients (Talaat et al. 2015).
- Dilute it, then drench and spray Agriton recommends diluting Actiferm 1:100, which is 10 ml to a litre of water, and spraying it on soil and plants. In the lettuce trial, a leaf spray added to a soil application gave one of the two best yields (Demir et al. 2024).
- Keep applying through the season The trials that found gains applied EM repeatedly: weekly to the end of flowering for beans (Iriti et al. 2019), and up to seven times for sweetcorn (Daly & Stewart 1999).
The evidence at a glance
The short version of every study this piece leans on. Click any study to jump to the full reference and a link to the paper.
| Study | What was tested | What it found |
|---|---|---|
| Megali et al. 2014 | Greenhouse tomato | Plant growth +35%, fruit production +61% |
| Megali et al. 2015 | Meta-analysis of 39 studies; nine-crop greenhouse test | Positive effect on growth and yield; greenhouse growth +16% |
| Olle & Williams 2013 | Review of EM vegetable studies | Growth positive in 70% of studies; yield positive in 84% of 22 reports |
| Xu et al. 2001 | EM on bokashi and chicken manure, tomato | Higher photosynthesis and fruit yield; more fruit vitamin C in every treatment |
| Demir et al. 2024 | Glasshouse lettuce, microbial culture + 75% chemical feed | Highest total yield in the trial, +6.7% vs full chemical rate |
| Iriti et al. 2019 | Greenhouse beans, weekly EM-1 soil drench | Peak photosynthesis held two weeks longer; more seed on every medium |
| Daly & Stewart 1999 | EM + molasses, organic farms, New Zealand | Onion +29%, pea +31%, sweetcorn cob +23% |
| Hu & Qi 2013 | EM compost vs plain compost, 11-year wheat trial | Higher straw biomass, grain yield and grain nutrition |
| Jusoh et al. 2013 | Rice straw, goat manure and green waste compost | Significantly more N, P and K with EM |
| Feng et al. 2026 | Mushroom residue and chicken manure compost | Shorter heating phase; better maize roots and yield |
| Talaat et al. 2015 | Beans on salty soil | Better growth; higher uptake of N, P, K, Ca, Mg, Fe, Zn and Cu |
Eleven peer-reviewed studies. Bold green marks the headline figure for each row.
Read together, the trials point one way: activated EM-1 earns its place alongside compost, bokashi and other organic matter, applied regularly through the season.
Try it yourself
Put a box to work this week
Start with ready-made Actiferm: add it to your compost heap or bokashi bin, spread the finished compost on your beds, and keep it going through the season.
Shop ActifermWritten by Joseph Barrington, founder of Dr Forest, a maker of handcrafted organic fertilisers in Stockport, Greater Manchester.
Frequently asked questions
Is activated EM-1 a fertiliser?
It is a microbial inoculant rather than a bag of feed. Its work is biological: lactic acid bacteria can make the nutrients in compost and other organic material more available and stimulate plant growth (Lamont et al. 2017). That is why it pairs so well with compost and bokashi.
How should I store Actiferm?
Agriton advises keeping it somewhere cool and dark. It comes in a bag-in-box, so you draw off what you need through the tap without letting air back into the bag.
Does it work in different soils and growing media?
In the bean trial, EM raised seed yield on every growing medium tested (Iriti et al. 2019), and on salty soil it improved bean growth (Talaat et al. 2015). Pair it with organic matter so the microbes have something to work on.
Can I use activated EM-1 on compost and as a foliar spray?
Yes. Both compost trials found more nutrients or faster composting with EM (Jusoh et al. 2013; Feng et al. 2026). In the lettuce trial, a leaf spray added to a soil application gave one of the two best yields (Demir et al. 2024). Agriton's dilution for spraying is 1:100, which is 10 ml per litre of water.
Sources cited
- Megali, L., Glauser, G. & Rasmann, S. (2014). Fertilization with beneficial microorganisms decreases tomato defenses against insect pests. Agronomy for Sustainable Development, 34, 649–656. doi.org/10.1007/s13593-013-0187-0
- Megali, L., Schlau, B. & Rasmann, S. (2015). Soil microbial inoculation increases corn yield and insect attack. Agronomy for Sustainable Development, 35, 1511–1519. doi.org/10.1007/s13593-015-0323-0
- Olle, M. & Williams, I.H. (2013). Effective microorganisms and their influence on vegetable production – a review. Journal of Horticultural Science & Biotechnology, 88(4), 380–386. doi.org/10.1080/14620316.2013.11512979
- Iriti, M., Scarafoni, A., Pierce, S., Castorina, G. & Vitalini, S. (2019). Soil application of effective microorganisms (EM) maintains leaf photosynthetic efficiency, increases seed yield and quality traits of bean (Phaseolus vulgaris L.) plants grown on different substrates. International Journal of Molecular Sciences, 20(9), 2327. doi.org/10.3390/ijms20092327
- Xu, H.-L., Wang, R. & Mridha, M.A.U. (2001). Effects of organic fertilizers and a microbial inoculant on leaf photosynthesis and fruit yield and quality of tomato plants. Journal of Crop Production, 3(1), 173–182. doi.org/10.1300/J144v03n01_15
- Demir, H., Saka, A.K., Uçan, U., Akgün, İ.H. & Yalçı, H.K. (2024). Impact of effective micro-organisms (EM) on the yield, growth and bio-chemical properties of lettuce when applied to soil and leaves. BMC Plant Biology, 24, 1189. doi.org/10.1186/s12870-024-05980-y
- Daly, M.J. & Stewart, D.P.C. (1999). Influence of "effective microorganisms" (EM) on vegetable production and carbon mineralization – a preliminary investigation. Journal of Sustainable Agriculture, 14(2–3), 15–25. doi.org/10.1300/J064v14n02_04
- Hu, C. & Qi, Y. (2013). Long-term effective microorganisms application promote growth and increase yields and nutrition of wheat in China. European Journal of Agronomy, 46, 63–67. doi.org/10.1016/j.eja.2012.12.003
- Jusoh, M.L.C., Manaf, L.A. & Latiff, P.A. (2013). Composting of rice straw with effective microorganisms (EM) and its influence on compost quality. Iranian Journal of Environmental Health Science & Engineering, 10, 17. doi.org/10.1186/1735-2746-10-17
- Feng, Y. et al. (2026). Effects of Effective Microorganism (EM) inoculation on co-composting of Auricularia heimuer residue with chicken manure and subsequent maize growth. Microorganisms, 14(1), 106. doi.org/10.3390/microorganisms14010106
- Lamont, J.R., Wilkins, O., Bywater-Ekegärd, M. & Smith, D.L. (2017). From yogurt to yield: potential applications of lactic acid bacteria in plant production. Soil Biology and Biochemistry, 111, 1–9. doi.org/10.1016/j.soilbio.2017.03.015
- Talaat, N.B., Ghoniem, A.E., Abdelhamid, M.T. & Shawky, B.T. (2015). Effective microorganisms improve growth performance, alter nutrients acquisition and induce compatible solutes accumulation in common bean (Phaseolus vulgaris L.) plants subjected to salinity stress. Plant Growth Regulation, 75, 281–295. doi.org/10.1007/s10725-014-9952-6
- Talaat, N.B. (2015). Effective microorganisms improve growth performance and modulate the ROS-scavenging system in common bean (Phaseolus vulgaris L.) plants exposed to salinity stress. Journal of Plant Growth Regulation, 34, 35–46. doi.org/10.1007/s00344-014-9440-2
