Effective microorganisms, or 'EM' for short, is a purposefully compound mixture of naturally occurring microorganisms, sometimes used to inoculate plants and soils to improve soil quality and plant growth. EM are composed of many microbial species. Among the most important are photosynthetically active bacteria, lactic acid bacteria and yeasts. These microorganisms live symbiotically, which means they support each other.
The use of EM aims to stabilize the microbial environment in general and to shift it in a direction that is ideal for the respective purpose of application. For example, microorganisms such as putrefactive agents are very important in nature for degradation and conversion processes, however they are undesirable in the storage of food products. In that case, different species in EM solutions can contain the spread of putrefactive agents and suppress other pathogens. In the field of plant production or soil remediation, EM can enrich the diversity of organisms that, among other things, break down nutrients in soil so that they can be more easily absorbed by plants. In numerous studies, an increase in yield and quality in plant production as well as an increase in soil quality through a higher vitality of soil life have been observed after inoculation of EM. Also in the field of animal husbandry, EM is sprayed to relieve odors, germs and rot, as well as to enhance the value of the manure already in the barn. Other new areas of application are cosmetics, personal hygiene, food supplements and drinking water purification.
Research results on the qualities of EM as an organic fertilizer are already made available, from which a positive fertilizing effect can be derived. One EM application also known in the Western cultural area is Bokashi. Bokashi means fermented potpourri, which in Japan consists mainly of rice bran, oil mill press cake or fish remains. This is fermented with EM. By doing so, an improved soil quality could be observed in some experiments.
The term EM and the concept of 'good microorganisms' was coined in the 1980s by the Japanese horticulture professor Teruo Higa. Originally, he developed EM as a soil additive that can be used to reduce mineral fertilizers and pesticides. In the beginning EM spread throughout Japan, the country of origin, and some countries of the Global South like Thailand and Brazil, where it was included in the production of Terra Preta. In the past twenty years, EM has found its way to Europe.
A digital global EM community has established itself on the Internet and generates a lively exchange of knowledge. This has opened up a large number of new areas of application in addition to improving soil quality, such as applications for humans (drinking water treatment, intestinal cleansing, food supplements), in animal husbandry (stable and cage cleaning, animal care, feed supplements, appetite stimulants, infection treatment, wound healing), in water (natural cleaning of ponds and lakes), in waste management (odor prevention) and in the household (care and cleaning products). Due to the good networking of the worldwide EM community, there is a large number of instructions and seminars on the making and growth of EM. In many countries, newly founded companies with their own EM brands are on the rise. In Germany, too, there are already research projects and some companies offer a wide range of EM products. There is still plenty of scope for the exchange of experiences between players from Germany and Europe.
A frequent criticism is that EM experiments are not easily replicable by non-professionals, due to the complex knowledge required regarding the composition of EM. In addition, despite various research projects with first positive results, there remains a lack of multi-year studies that can reliably prove a positive effect. However, there is also a lack of studies which could prove the contrary- a risk to humans, animals or the environment deriving from the use of EM. In contrast to EM as soil additives, the majority of EM solutions for body treatment and drinking are not yet legally approved in Europe. Doctors in particular tend to view them with skepticism.
The purpose of using EM solutions to increase the feed intake of animals should be treated with caution in light of the underlying monetary incentive for livestock farmers. Excessive use in that case could lead to negative health consequences for farm animals.
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 Asia-Pacific Natural Agriculture Network (1995): EM application manual for APNAN countries. M. Shintani. Asia-Pacific Natural Agriculture Network, Bangkok, Thailand.
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