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.
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.
 Higa, T., & Parr, J. F. (1994): Beneficial and effective microorganisms for a sustainable agriculture and environment. International Nature Farming Research Center; Iwahori, H. and T. Nakagawara (1996): Studies on EM application in nature farming V. Applying methods of EM bokashi in vegetable culture. Annual Meeting of Japanese Society of Soil Science and Plant Nutrition. Tokyo.; Iwashi, p. (1994): Effects of EM bokashi on various paddy-rice varieties. Annual Meeting of Asia-Pacific Nature Agriculture Network.; Suzuki, Y. (1985): Effects of effective microorganisms on yield and quality of gin-seng herbs. Symposium of Applied Soil Microbiology. November 22, 1985, Urazoe, Okinawa.
 Asia-Pacific Natural Agriculture Network (1995): EM application manual for APNAN countries. M. Shintani. Asia-Pacific Natural Agriculture Network, Bangkok, Thailand.
 Higa, T., & Parr, J. F. (1994): Beneficial and effective microorganisms for a sustainable agriculture and environment. International Nature Farming Research Center.
 Shokouhian, A.A. (2019): The effect of application of EM Bio fertilizer and Urea on Strawberry (Fragaria ananassa cv. Paros) for Sustainable Agriculture. Journal of Water and Soil Conservation, Vol. 26(2), 2019; DOI: 10.22069/jwsc.2019.14138.2886
 Noparatraraporn, N. (1996): Thailand collaborative research on evaluation of EM and EMproducts, their feasibility testing and effects of their uses on agriculture and environment. Open Symposium: Present Situations and Prospects of Microorganismsas Agricultural Materials. August 1996, Tokyo.
 BBIB (2019): Vielfalt in der Uckermark. Forschungsprojekte 2015-2018. University of Potsdam. Free University of Berlin. Leibniz Centre for Agricultural Landscape Research (ZALF). June 2019: Brunswick. pp. 34-39.
 Higa, T., & Parr, J. F. (1994): Beneficial and effective microorganisms for a sustainable agriculture and environment. International Nature Farming Research Center. pp. 7-8.
 Rackl, C. (2006): Praktische Erfahrungen mit effektiven Mikroorganismen (EM) in Pflanzenbau und Tierhaltung. Fachhochschule Weihenstephan. p. 87.