Soil is the home for different kinds of organisms and microorganisms such as fungi, protozoa,earthworm,nematodes,actinomycetes,bacteria etc.Each of these organisms have essential role to boost up the soil and plant health.It is estimated that ,in one acre of living top soil there are about 2400 pounds of fungi ,1500 pounds of bacteria,133 pounds protozoa,900 pounds of earthworm ,890 pounds arthropods and other many organisms.soil can be viewed as stomach of the earth as there are the process of consumption,digestion,and cycling of nutrients .organic matters gets breakdown by soil organisms and make nutrient uptake for plants.The nutrient stored in the bodies of soil organisms prevent nutrient loss by leaching.There is a complex network of soil organism with food web with some subsisting on living plants and animals (herbivorous and predators),others on dead plant debris (detrivorus) on fungi or on bacteria.Some of the soil organisms and its role are described as fallows:

 Earthworm:

Earthworms are lucrative for the farmers in the agricultural field.The role of earthworm is diverse in the soil.On the basis of ecological category of species ,the influence of earthworm in the soil is different.

1.    Epigeic:  These are small and pigmented (green or reddish) earthworm which thrives mostly in the litter layer changing environment ,drought condition and high temperature. They are mostly used in compost making process.

2.    Endogeic:  These are the unpigmented worms that live and feed in the soil .It can be further divided into three groups i.e. oligohumic,mesohumic,and polyhumic.They carries the activities such as mixing and burrowing of soil.

3.    Anecic:  These are the earthworms that mostly spend their time in the soil .They feed on the surface litter that generally mix with soil.

 Furthermore,the fields that are tilled by the earthworm can absorb water at the rate of 4 to 10 times that of field lacking worm tillage .vertical earthworm burrows deep into the soil ,influence the microbial nutrient recycling process at the deeper level.In addition the mucus of the earthworm guts enhance the activity of other beneficial soil microorganism.It is studied that, if the number of worms are 6 per foot square then it need plow in Soyabean field .If the number of worms 14 per foot square in soyabean field then does not need any tillage operation.Hence, as  rule if the number of earthworm increased then required number of tillage operation decreased.

 Fungi: These are organisms responsible mainly for decomposition process in the terrestrial ecosystem. They have the ability to produce a wide variety of extracellular enzymes due to which they are able to breakdown all kinds of organic matter ,decomposing soil components and thereby regulating the balance of carbon and nutrients. Several species of fungi have the capacity to act as biosorbent of toxic metals such as cadmium,copper,mercury ,lead and zinc by accumulating in their fruiting bodies.It also performs well being functions related to water dynamics,nutrient cycling and diseases suppression .Few of the fungi produces the antibodies known as penicillin. Mycorrhizae fungi helps to extends the root hairs into the soil and increase the uptake of water and nutrients especially phosphorus.

Bacteria: Each gram of soil contains approximately one million of these tiny one celled organism.Bacteria are often called as bag of enzymes or soluble bag of fertilizer.There are  different species of bacteria,each have their own respected role in soil biology.Bacteria plays important role in nutrient cycling as well as release of Nitrogen, Sulphur ,phosphorous and many other trace elements from organic matter.Bacteria like Nostoc,Rhizobium infects the root and begin to multiply colonize,hence forming the root nodules in the legumes .Symbiotically,they convert atmospheric nitrogen into ammonia. Non symbiotic nitrogen fixation is done by Azobacter,Rhodospirlan etc . Furthermore, bacteria also involve in the solubility of nutrients improving soil structure ,fighting root diseases and detoxifying soil.

 Nematodes: Their are many groups of nematodes present in agricultural soil .Some of them are bacterial feeder ,fungal feeder ,plant parasites ,predators etc.Through the feeding interaction of nematodes ,they are directly involve in nutrient mineralization process. Bacterial feeding nematodes absorb nitrogen and other N –containing compounds in bacterial tissue and convert nitrogen in the form of ammonium ion which is readily available for plant.

References:

http://unsplash.com/photos/jin4w1HqgL4

http://fao.org/3/a0100e/a0100e0d.htm

http://www.attra.ncat.org/sustainable soil management