Bio fertilizer and Soil fertility

Bio fertilizer is a large population of a specific or a group of beneficial microorganisms for enhancing the productivity of soil. It is fixing atmospheric nitrogen by solubilizing soil phosphorus.

Bio fertilizer and Soil fertilityIt is also increase the plant growth by producing the growth promoting substance. Bio-fertilizers can expect to reduce the use of chemical fertilizers and pesticides. The microorganism in bio-fertilizers restores the soil’s natural nutrient cycle and builds soil organic matter. By the application of bio-fertilizers, healthy plants can be grown, while increasing the sustainability of soil and the health of the soil.

Example: Rhizobium, Azotobacter, Azospirilium and blue green algae (BGA)

Importance of Bio fertilizer

  • Increase the yield of plants about 15-35%.
  • Effective even under semi-arid conditions.
  • Farmers can prepare the inoculum themselves
  • Do not allow pathogens to flourish.
  • Produce growth promoting bio-chemical
  • Non-polluting.

Various Types of Bio fertilizer

  • Free Living Nitrogen Fixing Bacteria
  • Cyanobacteria Free Living Nitrogen Fixing
  • Symbiotic Nitrogen Fixing Bacteria
  • Microphos Bio fertilizers
  • Mycorrhiz

Free Living Nitrogen Fixing Bacteria 

They are live freely in the soil and perform nitrogen fixation. They may be saprotrophic, living on organic remains. For Example: Azotobacter and Clostridium. The property of nitrogen fixation is also found in photoautotrophic bacteria, e.g. Rhodopseudomonas, Rhodospirillum, Chromatium. The process of Inoculation of soil with these bacteria helps in increasing yield and saving of nitrogen fertilizers. Azotobacter occur in fields of Rice and Cotton not only in increases yield but also saves nitrogen fertilizer to the tune of 10-25 kg/ha.

Cyanobacteria Free Living Nitrogen Fixing

A number of free living cyanobacteria or blue-green algae have the ability of nitrogen fixation. For Example. Anabaena, Nostoc, Aulosira, Totypothrix, Cylindrospermum, Stigonema. Cyanobacteria are photosynthetic. So that they can add organic matter as well as extra nitrogen to the soil. Cyanobacteria are extremely low cost bio-fertilizers. In the south Indian state Tamil Nadu, the technique of cyanobacteria inoculation to rice fields is being followed. Phosphate and Molybdenum are supplied additionally.

Symbiotic Nitrogen Fixing Bacteria:

They form a mutually beneficial association with the plants. The bacteria obtain food and shelter from plants. In return, they give them a part of their fixed nitrogen to the plants. The most important of the symbiotic nitrogen fixing bacteria is Rhizobium. It forms nodules on the roots of legume plants. There are about a dozen species of Rhizobium. They form association with different legume roots. For Example R. legumin Sarum and R. lupini.

Microphos Bio fertilizer:

They release phosphate and insoluble states, e.g., Bacillus polymyxa, Pseudomonas striate, Aspergillus species


It is a mutually beneficial symbiotic association of a fungus with the root of a higher plant. The most common fungal partners are Glomus species. Mycorrhizal roots show a sparse or dense woolly growth of fungal hyphae on their surface. The root hair and root cap are absent. The shape is irregular, tuberous and nodulated.


Soil fertility refers as “The ability of the soil to sustain plant growth” i.e. to provide plant habitat and result yields of high quality. A fertile soil have these properties: It is rich in nutrients necessary for plant nutrition, including nitrogen, phosphorus and potassium. Maintain the soil Fertility maintain the yield every year

Assessment of fertility

In most situations the best assessment of soil fertility and site can be derived from knowledge of the history of a site and observation of the vegetation growing there and in similar conditions in the locality.

  1. Chemical analysis

Chemical analysis of soil fertility is complex subject and is often of limited practical use for wild flower growing.  There is no simple way of assessing the ability of a soil to supply plants with the most important soil nutrients Nitrogen, and now these days most established soil test methods have been developed to guide farmers and growers as to how much fertilizer we should add to obtain maximum crop yields. Within the 0-9 range over which farm test results are classified the natural level of most interest for diversity are found in the lowest 0 or 1 class.

  • Soil phosphorous (P)

The phosphate quantity in the soil is considered to be the most useful chemical indicator of fertility and thus potential plant diversity. This is not because phosphorous can greatly increases the productivity of crops but that its status is frequently the factor that limits plants ability to exploit other resources.

Human activity:

Human and animal wastes, the addition of basic slag and artificial fertilizers have together augmented the level found in gardens and farmed land to a level 2 or more Unfortunately once raised soil P levels decline incredibly slowly, so slowly in fact that elevated Phosphorous levels are used by archaeologists to detect ancient settlement patterns and abandoned farmsteads these often reveal themselves as patches of nettles which thrive on high phosphate levels.

Factors that reduce the Soil Fertility

  • Leaching of soil Nutrient
  • Repeated removal of bulky crops
  • Deep ploughing to bury nutrients

Role of Bio Fertilizers in soil fertility and Agriculture

Bio fertilizers are known to play a number of vital roles in soil fertility crop productivity and production in agriculture as well as they are Eco-friendly and cannot replace chemical fertilizers at any cost that are indispensable for getting maximum crop yield.

Some of the important function or roles of Bio fertilizers in agriculture are:

  • They are supplement chemicals fertilizers for completing the requirement of integrated nutrient demand of the crops.
  • They can add 20-200 kg N/ha year under optimum soil conditions and thereby increases 15-25 percent of total crop yield.
  • They minimize the use of chemical fertilizers and not exceeding of 40-50 kg N/ha under ideal agronomic and pest-free conditions.
  • They liberate growth increasing substances and vitamins and help to maintain soil fertility. These are cheaper, pollution free and energy sources.
  • They improve physical properties of soil, soil tilth and soil health in general.
  • They also improve the soil fertility and soil productivity.
  • The BGA like Nostoc, Anabaena, and Scytonemaare often employed in the reclamation of alkaline soils. BGA plays a vital role in the nitrogen economy of rice fields in tropical regions.

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