E- Content M.Sc Semester II MBOTCC-5: Biofertilizer Technology, Unit 1

Name of Faculty: Dr Tanuja, University Department of Botany, Patliputra University

Topic: Introduction to biofertilizers

The term “Biofertilizer” or more appropriately “Microbial inoculants” can generally be

defined as preparation containing live or latent cells of efficient strains of nitrogen fixing,

phosphate solubilizing or cellulolytic microorganism used for application to seeds, soils or

composting areas with the objective of increasing the number of such microorganisms and

accelerate those microbial process which augment the availability of nutrients that can be

easily assimilated by plants.

Biofertilizers, being biological in origin are considred to be relatively safe and sustainable.

They are capable of supplying not only major nutrients but also micronutrients for effective

growth of plants. Most of the biofertilizers are produced through involvement of

microorganisms.

Since biofertilizers can successfully be used in many variety of crops grown under different

agro-ecologies, their potential requirement is quite large and is reported to far exceed the

present production levels. It is assumed that biofertilizers can substitute about 25% of the

nutrient requirement of the crops. Nitrogen is a key component of nutrients for plants.

Inputs of biologically fixed Nitrogen into agricultural systems are derived from symbiotic

relationship between legume and Rhizobium, as well as due to non-symbiotic association

between free living diazotophs and plant roots.

Biofertilizer improves soil particles and sustain soil fertility. It has been reported that the

benefit to cost ratio of biofertilizer is fairly high. Some authors have reported that

biofertilizers harness atmospheric nitrogen and make it available directly to the plant.

According to Subba Rao, 1993,it helps in increasing phosphorous uptake and releasing

unavailable phosphorous. It enhances root proliferation due to release of growth promoting

hormones .

Benefits of Biofertilizers

It helps in maintaining environmental health by reducing the level of pollution.

Reduces human & animal hazards by reducing the level of residue in the product.

Increases the agricultural products and makes it sustainable

Ensures the optimum utilization of natural resources.

Reduces the risk of crop failure.

Improves the physical and chemical properties of soil

Biofertilizers are cost-effective when compared to synthetic fertilizers

Using biofertilizers can increase crop yield by 20 or 30 percent.

Drawbacks of Biofertilizers

Slow-release

Crop specific

Strain-specific

Soil specific—lose effectiveness if soil too dry or hot

Lesser efficient than synthetic fertilizers

Crops show less response to biofertilizers then chemical fertilizers

Much lower nutrient density — requires large amounts to get enough for most crops.

HISTORICAL DEVELOPMENT OF BIOFERTILIZERS

Inoculation of plants with beneficial bacteria can be traced back to centuries. Although

bacteria were not proven to exist until Von Leeuwenhoek in 1683 discovered microscopic

‘animals’, their utilization to stimulate plant growth 3 in agriculture has been exploited since

ancient times. Theophrastus (372-287 BC) suggested the mixing of different soils as a means

of remedying defects and adding heart to the soil . From experience farmers knew that

when they mixed soil, taken from previous legume crop with soil in which non-legumes

were to be grown, yields often improved. By the end of the 19th century, the practice of

mixing “naturally inoculated” soil with seeds became a recommended method of legume

inoculation in the U.S.A. A decade later, the first patent (“Nitragin”) was registered for plant

inoculation with Rhizobium sp. Eventually the practice of legume inoculation with non-

symbiotic, associative rhizosphere bacteria, like Azotobacter, was used on a large scale in

Russia in 1930s and 1940s. Bacillus megaterium for phosphate solublization was used in the

1930s on large scale in Eastern Europe.

In India, from 1920 onwards Joshi Desai, Vyas, Biswas and Acharya worked on phosphate

requirements of legumes for better recuperation of soil nitrogen and on anaerobic digestion

of organic matter at Imperial Agricultural Research Institute. At the same time, Madhok

introduced the practice of using bacterial cultures for beerseem (Trifolium alexandrium) in

Punjab. Sanyasi Raju and Rajagopalan worked on root nodulation of Bengal gram and

groundnut at the Madras Agricultural College, Coimbatore (Subbarao, 1977).

The production of rhizobial inoculants was first undertaken at IARI, New Delhi in 1956

although its commercialization started in late 1960s when soybean was introduced for the

first time in the country. Inoculants for pulses, oilseeds and fodder legumes were also

produced. The processes of development of rhizobial inoculants for various 4 legumes in

India has made considerable progress following the field evaluation of the inoculants on

yields of various pulses, soybean, groundnut and fodder legumes was carried under the All

India Coordinated Research Programmes of the respective crops by the Indian Council of

Agricultural Research, New Delhi. The use of inoculants has considerably increased over the

years and a number of private producers have come into operation. It is therefore,

imperative to control the quality of inoculants.

Accordingly, the Bureau of Indian Standards has sprung into action and specific standards

for Rhizobium, Azotobacter, Azospirillum and phosphate solublizing bacterial inoculants

have been brought out. Some of the nitrogen fixers colonize the root zones and fix nitrogen

in loose association with plants. A very important bacterium of this category is Azospirillum

which was discovered by Brazilian scientist, J. Dobereiner. In the late 1970s Azospirillum was

found to enhance non-legume plant growth. In recent years, various other rhizobacteria

such as Aeromonas veronii, Azotobacter sp., Azoarus sp, Cyanobacteria (predominantly of

the genera Anabaena and Nostoc) Alcaligenas, Burkholderia, Comamonas acidororans,

Enterobacter, Erwinia, Flavobacterium, rhizobia (including the Allorhizobium, Azorhizobium,

Bradyrhizoblum, Mesorhizobium, Rhizobium and Sinorhizobium) Gluconacetobacter

diazotrophicus, Herbaspirillum seroepdicae, Serratia, Variovorax paradoxus and

Xanthomonas maltophilia have been identified for their use either as biofertilizers or

biological control agents (Bioinoculants).

TYPES OF BIOFERTILIZERS :There are various types of biofertilizers which are as follows:

(a) Nitrogen-fixing biofertilizers:

(i) Symbiotic nitrogen fixers - Rhizobium

(ii) Non-symbiotic nitrogen fixers

- Azotobacter

- Azospirillum

- Blue green algae (Nostoc,Anabaena etc)

– Azolla

(b) Phosphorous mobilizing biofertilizers:

(i) Phosphate solublizer

- Bacillus

- Pseudomonas

- Aspergillus niger

(ii) Phosphate absorber

- VAM fungi (eg) Glomus, Gigaspora

(c) Organic matter decomposer biofertilizers

(i) Cellylolytic

- Cellulomonus

- Trichoderma

(ii) Lignolytic

- Arthrobacter

- Agaricus

Some images of biofertilizers:

Anabaena azollae Nostoc

Azolla Azotobacter(petri plate) After Gram Staining

Root nodule Rhizobium streaked on petriplate After Gram staining

Cellulomonas (on petri plate) Different isolated spores of VAM