Fungi
These are not the most abundant of the soil organisms, but they account for the greatest amounts of living mass which are in the soil. Fungi are multicellular and do not contain chlorophyll, therefore, they cannot manufacture food on their own. Familiar examples include mildews, molds, rusts and mushrooms. Fungi can be pathogenic to turf grasses; they can also benefit turf by improving the soil aggregation and decomposing complex organic residues. Some fungi enter into a mutually beneficial relationship with roots of plants. This is well-documented with mycorrhizal fungi and trees. Mycorrhizal relationships in turf grasses are not well understood, but have been reported in turf grass soil high numbers of mycorrhizae. Mycorrhizae also may provide some resistance to various stresses by increasing available soil volume for water and nutrient acquisition.
These are not the most abundant of the soil organisms, but they account for the greatest amounts of living mass which are in the soil. Fungi are multicellular and do not contain chlorophyll, therefore, they cannot manufacture food on their own. Familiar examples include mildews, molds, rusts and mushrooms. Fungi can be pathogenic to turf grasses; they can also benefit turf by improving the soil aggregation and decomposing complex organic residues. Some fungi enter into a mutually beneficial relationship with roots of plants. This is well-documented with mycorrhizal fungi and trees. Mycorrhizal relationships in turf grasses are not well understood, but have been reported in turf grass soil high numbers of mycorrhizae. Mycorrhizae also may provide some resistance to various stresses by increasing available soil volume for water and nutrient acquisition.
Bacteria
These are the most abundant of the soil organisms (>100 million per gram or teaspoon of soil) and are the most important within the top 6 inches of the soil. Bacteria are small single-celled microorganisms that reproduce by cell division. There is great diversity which exists among bacteria: some species are aerobic, some anaerobic, some autotrophs and others heterotrophs. Compared to cultivated agricultural soils, bacteria populations are generally greater in grassland soils because of higher root densities, available nutrients and organic matter content that are present. Like many soil organisms, bacteria are influenced by soil temperature, water content and pH. Soil bacteria populations, therefore, fluctuate with the season. Due to a quick generation time (as fast as 20 minutes between cell divisions), bacteria can quickly colonize and exploit organic materials once conditions for growth become favorable.
Actinomycetes
These are believed to be an evolutionary transition between bacteria and fungi due to the fact that they have characteristics of both organisms. They are single-celled microorganisms lacking chlorophyll. Based on numbers, they are next to bacteria in abundance in the soil. Actinomycetes are considered to be slow growing; they are late colonizing organisms responsible for degradation of complex molecules like cellulose, phospholipids chitin and lignin. Actinomycetes produce antibiotics and volatile substances that give soil a sweet, rich, earthy flavor. They are sensitive to pH changes, with populations being greatest at pH values above 6.0 and almost nonexistent at pH 5.0. Their exact roles in turf grass soil biosphere are not clearly understood.
Protozoa
Protozoa are generally found in the upper 6 inches of the soil, protozoa are the most abundant of the soil-inhabiting organisms that can be considered animal life. Protozoans include amoeba and paramecium, which feed on organic matter and other soil microbes. Little is known of soil protozoa, but they regulate bacterial populations through predation and competition. There are no known diseases of turf grass as a result of protozoa.
Algae
Algae are multicellular organisms with chlorophyll and, are autotrophic in their nutritional requirements. This means, they must reside close to the soil surface where light for photosynthesis is abundant. Examples include cyanobacteria (blue-green algae), green algae and diatoms. Algae reproduce by simple cell division and have cell walls similar to higher plants, considered the early colonizing organisms in natural habitats, the presents of algae are important in initial stages of soil formation. Algae also can form crusts or mats that seal the soil surface, effecting water infiltration, water retention and soil/air gas exchange and influencing seed germination. Buried algae mats have also been associated with the physical, chemical and biological condition known as black layer.
Nematodes
These are microscopic round worms that can comprise as much as 90 percent of the multicellular invertebrates that are in soil. A few square feet of soil can inhabit millions of nematodes. Nematodes are reproduced by eggs and are most prevalent in warm, moist, sandy soils. They are essential in the soil food web, even in the recycling of soil nutrients. Like many other microorganisms, nematodes can positively affect soil.
Larger organisms
Earthworms, grubs, slugs, mole crickets, ants and mites include in the soil-inhabitance of animals and insects. These organisms mostly affect grass by churning the soil while feeding, which aids aggregation, water movement, aeration and thatch degradation. Not only is the soil composed of sand, silt, clay, air and water, it is also a living, breathing, it’s a dynamic environment which containing a broad diversity of organisms. These serve vital functions in the root zone, most are beneficial but some are detrimental
Viruses
These are sub-microscopic organisms with a relatively simple structure, a DNA or RNA core and an encasing protein coat. Viruses are the intracellular parasites that do not respire or metabolize and must have a biological host to reproduce. Soils may harbor many viruses, but it is believed that they do not directly affect the characteristics soil.
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| Soil organisms |
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