A biofertilizer (also bio-fertilizer) is defined as a substance which contains living microorganisms which, when applied to seed, plant surfaces, or soil, colonizes the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant.
Plants have a symbiotic relationships with fungi, bacteria, and algae, the most common of which are with mycorrhiza, rhizobium, and cyanophyceae. These are known to deliver a number of benefits including plant nutrition, disease resistance, and tolerance to adverse soil and climatic conditions.
Bio-fertilizers add nutrients through the natural processes of nitrogen fixation, solubilizing phosphorus, and stimulating plant growth through the synthesis of growth-promoting substances.
Through the use of bio-fertilizers, healthy plants can be grown, while enhancing the sustainability and the health of the soil. Since they play several roles, a preferred scientific term for such beneficial bacteria is “plant-growth promoting rhizobacteria” (PGPR). BIOFERTILIZERS
Since a bio-fertilizer is technically living, it can symbiotically associate with plant roots.
- Involved microorganisms could readily and safely convert complex organic material in simple compounds, so that plants can assimilate those nutrients easily .
- Microorganism in biofertilizers symbiotic function causes improvement of the soil fertility.
- Bio-fertilizers are cost-effective relative to chemical fertilizers. They have lower manufacturing costs, especially regarding nitrogen and phosphorus use that’s why it is farmers and cultivators friendly .
- Biofertilizers also provide protection against drought and some soil-borne diseases and hence it may be defined as the panacea of green eco friendly .
- It increases crop yield by 20-30%, replaces chemical nitrogen and phosphorus by 25%, and stimulates plant growth without altering the physical and chemical characteristics of the soil .
Types of BioFertilizers
nutrient solubilizing microbes
To enhance the crop production, management of quality soil is one of the ideal and sustainable approaches to overcome depleting soil fertility status and land degradation. Rhizospheric beneficial microorganisms may offer plant growth promotion, agronomic, pathogenic and environmental benefits for intensive agricultural system. Nitrogen fixing bacteria fixes atmospheric nitrogen in soil, while phospho-bacteria solubilizes insoluble fixed phosphorus in the soil, potassium mobilizing bacteria mobilizes immobile potassium in soil and similarly other microbes mobilize or solubilize element in soil and make it readily available to the plant. Nitrogen fixing bacteria includes symbiotic nitrogen fixing (N2 fixing) forms, in leguminous plants viz. Rhizobium, obligate symbionts and with non-leguminous plant includes spp. Achromobacter, Alcaligenes, Arthrobacter, Acetobacter, Azomonas, Beijerinckia, Bacillus. Phosphorus is major essential macro-nutrients for biological growth and development. Majority of soil phosphorous present in soil in insoluble form and cannot be utilized by plants. Species of Pseudomonas, Bacillus, Penicillium, Aspergillus secretes organic acids, lower pH in their vicinity to bring dissolution of bound phosphates in soil. Additionally inoculation of seed or seedling with microphos bio-fertilizers can provide 30 kg P2O5/ha. Potassium is associated with movement of water, nutrients, carbohydrates and cellular &osmotic pressure in plant tissue. If potassium is deficient or not supplied in adequate amount, growth is stunted and yields are reduced. Several bioinoculant of bacterial species has been reported to solubilize insoluble inorganic phosphate compound such as tri-calcium phosphate, di-calcium phosphate, hydroxyl-apatite and rock phosphate. Supplementation of zinc in the form of synthetic fertilizer is proved to be inappropriate due to its unavailability to the plants. In the recent past, bacteria have shown terrific ability to improve Zn availability in rhizosphere and enhance Zn in plant. In rice, silicate solubilizing bacteria has gaining importance in recent times because of their role in solubilization of silicate minerals rendering silica and potassium available for crop uptake, thus reducing potash fertilizer requirement.
Research paper: Nutrient solubilizing microbes: Its role in sustainable crop production. Available from: https://www.researchgate.net/publication/308153982_Nutrient_solubilizing_microbes_Its_role_in_sustainable_crop_production [accessed Apr 11, 2017].
fermented plant extracts
Fermented plant extracts (FPE) are also known as fermented plant juice (FPJ). FPJ is used in solutions for seed and soil treatments and plant nutrition.
The fermentation process, either performed passively or with the aid of brown sugar and/or Effective Microrganisms (EM-1), draws out the plants enzymes, hormones, vitamins and benefical microbiology.
The University of Hawaii has a great instructional booklet on FPJ.
Technically, compost tea is where beneficial microorganisms are extracted from compost, humus or vermicompost (worm compost). When provided with the right food source, their populations can effectively multiply into the billions. Jeff Lowenfels, the author of Teaming With Microbes, reports that the bacterial population in 1 teaspoon of compost can grow from 1 billion to 4 billion in an aerated compost tea (ACT). So when compost tea is brewed, you are literally creating life by facilitating the population growth of diverse groups of microorganisms. High quality compost tea will have all of these organisms working synergistically in the soil to optimize conditions that facilitate nutrient uptake and plant health. Many nutrients used in compost tea recipes function as a fertilizer for the plants as well.