Soil is a living organism. Soil innumerable bacteria, the number of them are associated with plant life. They are found in maximum quantity in soil. Millions of microorganisms are found in 1 gram of soil. All the reactions related to the dispersion of organic matter in the soil are driven by these organisms.
Let us describe some soil organism in detail.
They reside in all types of soil, they are circular or cylindrical or spindle-shaped, their posterior portion is pointed, their body length is about 40 -50 times greater than the width and the length of their entire body. They range from .5 to 1.4 m.m. They are found in myriad forms in the soil and they can be seen only with a microscope.
According to the requirement of food, they are divided into three classes.
1)Sporophyte;- Nematodes of this class use organic matter, microflora and protozoa from the rotten diet. They are omnivorous. They are high in the soil.
The nematodes of this class are violence-predaceous, they eat other animal-formulas in the soil – worms and other microorganisms. Predatory nematodes feed on soil microorganisms including plant-parasitic nematodes.
3)parasite nematodes;- Plant-parasitic nematodes are recognized as one of the greatest threats to crops throughout the world. Nematodes alone or in combination with other soil microorganisms have been found to attack almost every part of the plant including roots, stems, leaves, fruits and seeds
Protozoa plays an important role in mineralizing nutrients, making them available for use by plants and other soil organisms. Protozoa (and nematodes) have a lower concentration of nitrogen in their cells than the bacteria they eat. This usually occurs near the root system of a plant
Rhizopoda A phylum of the Protoctista that contains the amoebas and cellular slime molds. They are characterized by the possession of pseudopodia, which are used for locomotion and engulfing food particles.
Flagellates are very important predators on bacteria in the soil. Because of their high growth rates, flagellate populations respond rapidly to changes in bacterial numbers
Ciliates are the largest of the protozoa and the least numerous. They consume up to ten thousand bacteria per day and release plant-available nitrogen. Ciliates use the fine cilia along their bodies like oars to move rapidly through the soil.
The micro-organisms of this class meet and grow more in moist soil, are of silica-like shape and look like a dynamic circle.
In soil, several hundred species form three general groups: green, yellow-green (Xanthophyta) and diatoms (Bacillarophyta). Some are motile can be found a few centimeters below the surface although earthworms and rainwater may relocate them to further below the surface. Algal populations typically range from 10,000 – 100,000 cells per gram of soil. Being photosynthetic, algae play an important part in introducing organic matter into the soil and excrete polysaccharides which increase soil aggregation. Green algae prefer moist, non flooded acidic soils while diatoms prefer well-drained land rich in organic matter. When they die or dry up, they form, together with other soil microbes, a crust onto the soil which can prevent wind erosion and input organic matter into the soil.