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Soil environment consists of inorganic constituents ( minerals, water, air), dead matter and soil life. The living portion of the soil can be divided into macro- and micro- organisms.
Macroorganisms play an important role in organic decomposition, by chewing plants and animal resiudes into fine particles (soid minerals). Of consequence, the size of organic residues are being reducted.
Fertile soils is full of microbes. The most numerous microbes in soil are bacteria followed by Actinomyces ( responsible of the typical soil smell), fungi, cyanobacteria and protozoa. A little portion is occcupied by viruses. Soil microorganisms play an fundamental role in the continued recycling of nutrien which may be utilized by plants to energy production. These process is called mineralizzation.
Through mineralizzation, bacteria produce gummy substances which help to cement soil aggregates and stabilize the soil structure. Mineralizzation allows the organic elements recycling, such as carbon, nitrogen, phosphorus and sulfur, which come from crop residues, leaves organic waste. This organic residues are converted into simple inorganic compounds by control the quantities of avaiable nutrients for plants. All these inorganic particles compose the humus, an important layer of soil from which depends its fertility.
In the soil deep, where oxygen level is low or absent, we could find anaerobes bacteria. This latter grow best in neutral Ph value, at 15°-30°C.
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