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Soil microorganisms can be classified as bacteria, actinomycetes, fungi, algae and protozoa. Each of these groups has characteristics that define them and their functions in soil. [6] [7] Up to 10 billion bacterial cells inhabit each gram of soil in and around plant roots, a region known as the rhizosphere.
Soil biology is the study of microbial and faunal activity and ecology in soil. Soil life, soil biota, soil fauna, or edaphon is a collective term that encompasses all organisms that spend a significant portion of their life cycle within a soil profile, or at the soil-litter interface.
Soil microbial communities experience shifts in the diversity and composition during dehydration and rehydration cycles. [5] Soil moisture affects carbon cycling a phenomenon known as Birch effect. [6] [7] Temperature variations in soil are influenced by factors such as seasonality, environmental conditions, vegetation, and soil composition.
A method of maintaining ecosystem function in agricultural soils is using crop rotations, where increases in the number of crops used for a crop rotation in farming systems has also been shown to have the effect of increasing microbial diversity and the number of microbial species present. [17]
Soil has four important functions: as a medium for plant growth; as a means of water storage, supply, and purification; as a modifier of Earth's atmosphere; as a habitat for organisms; All of these functions, in their turn, modify the soil and its properties. Soil science has two basic branches of study: edaphology and pedology.
Free-living microfungi often function as decomposers, and contribute to soil microbial biomass. Many microfungi in biological soil crusts have adapted to the intense light conditions by evolving the ability to produce melanin, and are called black fungi or black yeasts. Fungal hyphae can bind soil particles together.
Soil microbial communities are characterized in many different ways. The activity of microbes can be measured by their respiration and carbon dioxide release. The cellular components of microbes can be extracted from soil and genetically profiled, or microbial biomass can be calculated by weighing the soil before and after fumigation.
Microorganism function is in long duration, causing improvement of the soil fertility. It maintains the natural habitat of the soil. It increases crop yield by 20-30%, replaces chemical nitrogen and phosphorus by 30%, and stimulates plant growth. It can also provide protection against drought and some soil-borne diseases.