BIOFERTILIZERS

·         Generally, the term "Fertilizer" is used for "Fertilizing material or Carrier", meaning any substance which contains one or more of the essential elements (nitrogen, phosphorus, potassium, sulphur, calcium, magnesium, iron, manganese, molybdenum, copper, boron, zinc, chlorine, sodium, cobalt, vanadium and silicon). Thus, fertilizers are used to improve the fertility of the land.

·         Biofertilizers may be defined as “Substances which contains living strains of microorganisms (Bacteria, Fungi and Algae) that colonize the Rhizosphere or the interior of the plants and promote growth by increasing the supply or availability of primary nutrients to the target crops, when applied to soils, seeds or plant surfaces”.

·         Biofertilizers infuse nutrients by natural processes such as synthesis of Growth promoting substances, Fixing nitrogen and Solubilizing phosphorous in the Rhizosphere.

NEED OF BIOFERTILIZERS

·         The heavy use of synthetic fertilizers for past many decades has led to depletion of essential nutrients from soil, contamination of the soil with harmful and non-degradable substances, pollution of water resources and destruction of friendly insects and essential microorganisms from the soil.

·         The global demand for fertilizers is much higher than the availability. The costs of chemical fertilizers are also increasing every other day, making them unaffordable by marginal and small farmers.

TYPES OF BIOFERTILIZERS

1)     Nitrogen fixers

a)     Free living or Asymbiotic or Non – symbiotic Nitrogen fixers

·         Aerobic Heterotrophs– Azotobacter sp., Achromobacter sp.  and Beijerinckia sp.

·         Aerobic Autotrophs– Nostoc sp., Anabaena sp., Colothrix sp. and Blue Green Algae (BGA)

·         Anaerobic Heterotrophs – Clostridium sp., Klebsiella sp. and Desulfovibrio sp.

·         Anaerobic Autotrophs – Chlorobium sp., Chromnaticum sp., Rhodospirillum sp. and Methanobacterium sp.

b)     Symbiotic Nitrogen fixers – Rhizobium sp., Bradyrhizobium sp., Azhorhizobium sp., Frankia sp., Blue Green Algae and Anabaena azollae

c)      Associative symbiotic Nitrogen fixers – Azospirillum sp. and Herbaspirillum sp.

d)     Endophytic Nitrogen fixers – Gluconacetobacter sp. and Burkholderia sp.

 

2)     Phosphorous solubilizers

a)     Bacteria – Bacillus megaterium var phosphaticum, Bacillus subtilis, Bacillus circulans, Bacillus polymyxa and Pseudomonas striata.

b)     Fungi – Aspergillus awamori and Penicillium sp.

3)     Phosphate mobilizers

a)     Arbuscular mycorrhiza (AM) – Glomus sp., Gigaspora sp., Acaulospora sp., Scutellospora sp. and Sclerocystis sp.

b)     Ectomycorrhiza – Laccaria sp., Pisolithus sp., Boletus sp. and Amanita sp.

c)      Ericoid mycorrhiza – Pezizella ericae

d)     Orchid mycorrhiza – Rhizoctonia solani

4)     Potassium mobilizers – Frateuria aurentia

5)     Silicate and Zinc solubilizers – Bacillus sp.

6)     Manganese solubilizers – Penicillium citrinum

7)     Silicate solubilizers – Bacillus mucilaginous

8)     Plant Growth Promoting Rhizobacteria (PGPR) – Pseudomonas fluorescence

ADVANTAGES OF BIOFERTILIZERS OVER CHEMICAL FERTILIZERS

1)     Biofertilizers have replaced the chemical fertilizers as chemical fertilizers are not beneficial for the plants. Chemical fertilizers decrease the growth of the plants and make the environment polluted by releasing harmful chemicals.

2)     Plant growth can be increased if biofertilizers are used, because they contain natural components which do not harm the plants.

3)     If the soil will be free of chemicals, it will retain its fertility which will be beneficial for the plants as well as the environment, because plants will be protected from getting any diseases and environment will be free of pollutants.

4)     Biofertilizers destroys harmful components from the soil which cause diseases in the plants.

5)      Biofertilizers are not costly and even poor farmers can make use of them.

6)      Biofertilizers are environment friendly and protect the environment against pollutants.

7)     Biofertilizers provides plant nutrients at very low cost.

8)     Biofertilizers helps for the survival of beneficial microorganisms in soil.

9)     Biofertilizers helps to get high yield of crops by making the soil rich with nutrients and useful microorganisms necessary for the growth of the plants.

10)Biofertilizers are also known to provide better nourishment to plants than chemical fertilizers.