Indigenous Microorganisms (IMOs) - An Overview - Japan - ARI
by the Asian Rural Institute
page developed by Rina Tanaka, ARI Volunteer
submitted July 2021
What are Indigenous Microorganisms?
This page introduces indigenous microorganisms (IMOs), which are microorganisms that we collect from local forests. We begin with a review of microorganisms in general, focusing on their functions and their needs. We then discuss the benefits of IMOs.
First, let's do a review of microorganisms. Microorganisms are tiny living creatures such as bacteria and fungi. They exist almost everywhere, but in nature, they play a vital role in the nutrient cycle. Along with worms and insects, they eat and decompose organic matter, which includes dead plants and animals, and release inorganic matter, which includes nutrients and other essential minerals for plants. Without them, nutrients would be consumed by plants with no replenishment and dead organisms would pile up on the floor with nowhere else to go.
As farmers, we also rely on soil organisms including microorganisms to break down soil organic matter and provide absorbable nutrients for plants. Microorganisms also help improve the soil by developing crumb structure in the soil and turning organic matter into humus. For more details on how soil organisms contribute to soil improvement, read the section "How can we improve soil quality?" on this page.
Microorganisms in soil actually do a lot more than *just* breaking down organic matter, supplying nutrients for plants, and making crumb structure. In soil, a diverse group of microorganisms play a variety of roles, such as preventing outbreaks of harmful microorganisms, fixing nitrogen, and even becoming food for earthworms that till the soil. We still do not fully understand all of the functions of microorganisms, but they are surely essential for soil health. (Note: There might be concerns about "harmful" microorganisms in soil including pathogen. However, if there is a diversity of soil organisms, there will be enough natural competitors and predators to prevent one kind from taking over.)
Our dependency on microorganisms can be seen in other aspects of life at ARI. We use them to make many things that involve fermentation, such as:
Bread and fermented food like natto and miso (Also, the microorganisms in our bodies help us digest food!)
Microorganisms thrive in bedding for livestock, where there is plenty of food and comfortable shelter for them. Animals also benefit from the work of microorganisms because the decomposition of their manure by the microorganisms reduces the odor.
How do we take care of microorganisms?
When we use microorganisms for soil improvement or fermentation, it is important to understand their needs and provide a good living environment for them. Otherwise, we will weaken or kill them. What is tricky here is that there are many kinds of microorganisms with different needs. For example, microorganisms that are active in bokashi are different from those active in fruit vinegar. Therefore, it is important to understand the types of microorganisms we want to increase in a particular context and adjust the environment to their needs.
Moisture: Like all living things, they need water, but the appropriate moisture content depends on the type of microorganisms.
Food: Microorganisms need sugar, protein, fat, and other minerals. We usually provide organic matter such as plant residues and manure or carbohydrates such as rice bran or crude sugar.
Aeration and access to oxygen: Some microorganisms require oxygen (aerobe); others do not or are even harmed by it (anaerobe), but might require gasses like nitrogen. Microorganisms involved in fermenting bokashi or compost need oxygen. Others, such as those that promote anaerobic fermentation in FPJ, do not need air or oxygen.
pH: Some microorganisms can live in highly acidic or alkaline environments, but most function better at a neutral pH level.
Temperature: In general, the growth of microorganisms tends to slow down as the temperature gets lower, however too much heat can kill certain microorganisms.
Sunlight: While some microorganisms can tolerate sunlight, others, such as those living in soil, will be killed by direct sunlight. This is why covering the soil with mulch or providing dark living spaces with charcoal is important to protect these microorganisms.
Where can we get microorganisms? - Indigenous microorganisms
Microorganisms exist everywhere, so they will eventually increase on their own if there is an adequate living environment for them. Indeed, we do not have to add any microorganisms to make compost for example; we wait for the microorganisms already existing on the organic matter to multiply by themselves. In fact, sometimes, all we can do is to wait; for example, when making fruit vinegar, we need to wait for the growth of a specific kind of microorganism which can be found on the surface of the fruits. However, for simple decomposition of organic matter, we sometimes want to add the appropriate microorganisms to organic matter to speed up the decomposition process, such as when we want to quickly make bokashi. Furthermore, a diverse population of microorganisms is necessary to completely decompose organic matter and prevent a few harmful types from dominating. Where can we get such a balanced collection of microorganisms?
It is true that we can buy special blends of microorganisms from stores, but at ARI, we believe that what we need is around us. We collect microorganisms from our local forests and call them indigenous microorganisms (IMOs). Not only are IMOs free and easy to collect, but they are also adapted to the local environment, which makes them resilient and effective for decomposition. Afterall, IMOs are collected from natural forests, where we can see complete decomposition of organic matter by a diverse group of soil organisms. To learn how to collect IMOs from forest soils, go to this page.
To meet the needs of IMOs, we usually mix them with food (rice bran, manure, plant residues) and living space (soil, charcoal).
To better understand how to meet the needs of IMOs, we will look at an example. We use IMOs in bokashi, so let's reflect on how we are creating an ideal environment for IMOs in the process of making bokashi.