Types of Biofertilizers

Types of Biofertilizers



The following types of biofertilizers are available to the
farmers in India.


☛ Nitrogen fixing biofertilizers eg. Rhizobium, Bradyrhizobium,
Azospirillum and Azotobacter.


☛ Phosphorous solubilising biofertilizers (PSB) eg.Bacillus,
Pseudomonas and Aspergillus


☛ Phosphate mobilizing biofertilizer eg. Mycorrhiza


☛ Plant growth promoting biofertilizers eg. Pseudomonas
How biofertilizers work?


☛ Biofertilizers fix atmospheric nitrogen in the soil and root
nodules of legume crops and make it available to the plant.


☛ They solubilize the insoluble forms of phosphates like tricalcium,
iron, and aluminium phosphates into available forms.


☛ They scavenge phosphate from soil layers.


☛ They produce hormones and anti metabolites which promote
root growth.


☛ They decompose organic matter and help in mineralization
in soil.


☛ When applied to seed or soil, biofertilizers increase the
availability of nutrients and improve the yields by 10 to
25% without adversely affecting the soil and environment.


Application and use

While some biofertilizers can be used for all crops, some
are crop specific. Depending on the biofertilizer, and the
crop grown, different methods of application are adopted. In
general, the performance of biofertilizers is more when used
along with organic manures like compost. In rainfed farming,
since moisture is limiting, best performance from biofertilizers
can be realized when moisture conservation practices are
adopted along with application of biofertilizers. The application
methods for different biofertilizers are described below.

Rhizobium (Bradyrhizobium)
This biofertilizer is recommended for

☛ Pulse legumes such as bengal gram, red gram, pea, lentil,
blackgram, greengram and cowpea

☛ Oilseed legumes like soybean and groundnut

☛ Fodder legumes like berseem and lucerne

☛ Tree legumes like Acacia, Leucaena and Gliricidia
The treatment of seeds with the slurry of Rhizobium
inoculant is the most effective method of application.

☛ Prepare the slurry of required quantity of inoculant in
sufficient water (generally 400-500 ml of water for
200 g inoculant). To prepare the slurry, boil 50 g gur in
one litre of water and cool it.

☛ Pour this slurry over the heap of seeds to be treated. Mix
the seeds thoroughly with hands. Now, spread the treated
seeds over clean floor or on plastic sheet or on gunny bag
and dry under shade.

☛ Sow the treated seeds as early as possible.


Dosage : 10 kg of normal size seeds such as moong, urd,
arhar, cowpea, lentil and berseem may be treated with 200
g of Rhizobium inoculant by slurry method. Large size seeds
such as groundnut, chickpea, soybean and pea, etc., require
400 to 500 g of inoculant for 10 to 12 kg of seeds. In case,
the seeds are to be treated with fungicides, insecticides and
bio agents, apply Rhizobium at the last. Apply Rhizobium
24 hr after treating with other chemicals.

Note : Best response for Rhizobium biofertilizer is realized
when recommended level of phosphorous is applied to the
legume crop.

Azospirillum
Azosprillum and Azotobactor can be used for most non
leguminous annual and perennial crops. Sorghum, pearlmillet,
maize and cotton are some examples. The methods of
application are:

☛ Seed treatment

☛ Seedling dipping

☛ Soil application
Seed treatment: Same as described for Rhizobium.

Dosage : 10 kg medium size seeds such as wheat, cotton,
maize etc., may be treated with 200 g of inoculant whereas,
100 g per acre inoculant is enough for treatment of very
small size seeds such as mustard.
Seedling dipping: This method is useful where the
transplantation of seedlings are required. It is ideal for
vegetable crops. The method of application is:

☛ Prepare the suspension of required amount of inoculant
in water in the ratio of 1:10.

☛ Dip the roots of seedlings in suspension and keep them
immersed for about 5 minutes

☛ Take out the seedlings from the suspension and transplant
as early as possible.