Question

Which one of the following is not a biofertilizer?
A. Agrobacterium
B. Rhizobium
C. Nostoc
D. Mycorrhiza

Answer 1

Hint: Fertilizers are materials of chemical or natural origin that are applied to the soil or plant surface to promote its growth by supplying one or more plant nutrients which are essential for the plant's growth. Chemical fertilizers increase pollution in the atmosphere because of which biofertilizers are being used nowadays.

Complete answer:
Biofertilizers are substances which contain living microorganisms which when applied to plant tissues, soil or seeds then they colonize the interior of the plant/ the rhizosphere of the plant and increase the supply of the primary nutrient to it thereby increasing its growth rate. Natural processes are being employed in providing nutrients to the plant like nitrogen fixation, phosphorus solubilisation, and production of growth promoting hormones that stimulate plant growth. Biofertilizers are very useful in maintaining the soil quality as the microorganisms present in it restore the soil’s natural nutrient cycle and build up organic matter in the soil. With the use of biofertilizers, use of synthetic or chemical fertilizers and pesticides can be avoided that cause harm to the sustainability of the soil and the atmosphere.
Biofertilizers like Azotobacter, Azospirillum, Rhizobium, blue green algae have been in use for a very long time. Azotobacter is used with crops like mustard, wheat, potato, maize, cotton and vegetable crops. Rhizobium is used as an inoculant for the leguminous crops. Azospirillum is used for millets, sugarcane, wheat, maize, and sorghum. Blue green algae including Nostoc, Aulosira, Anabaena are used in nitrogen fixation and are used as inoculants in paddy crops. All the Blue green algae belong to the Genus Cyanobacteria. Anabaena produces nitrogen in large quantities and enriches the soil with organic matter because of which it is used as manure. Fucus is also used as manure and in tropical areas where ponds have dried up the bottom mud which is rich in blue green algae is collected and used as manure. Usually a mixture made of blue green algae and seaweed works as an ideal manure or biofertilizer.

The answer for this question is Option A - Agrobacterium is not a biofertilizer. Agrobacterium is a gram negative bacteria used in the transfer of small DNA fragments into the plant genome by the process of transformation. It is known as nature’s genetic engineer as it creates transgenic or genetically modified crops and plants.

Note:
Biofertilizers are considered as living material as they contain microorganisms which live in symbiosis with the plant roots. In this symbiotic relation they help the plant to receive the essential primary nutrients and in return they reside in the plant roots and get food from the plants.