Biofertilizers & Biopesticides

Dr. Md. Osaid Alam

Guest Faculty
(Environmental Science & Management)
Department of Zoology
Patna University
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 Introduction

• Green revolution has revolutionized the world agriculture by increasing the yields
of food crops by the development of high-yielding varieties but the continuous and
excess use of chemical fertilizers has changed the soil characteristics to
acidic/alkaline leading to the reduction in the naturally occurring microorganisms
in soil that resulted in the stagnation/reduction in crop yields.
• In some areas the use of chemical pesticides and fertilizers has reached alarming
levels with grave implications for human health, the ecosystem and ground water.
• Use of microorganisms (biofertilizers and biopesticides) as an alternate to
synthetic fertilizers and pesticides to increase the soil fertility and disease and pest
control in agriculture is gaining prominence.
• Biofertilizers and biopesticides are environmental friendly products.

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 Biofertilizers

• Biofertilizers are considered to be an important alternative source of plant

nutrition.
• They are the preparations containing live or latent cells of efficient strains; micro-
organisms such as bacteria, algae or fungi used for application to seed, soil or
composting areas with the objective of increasing number of such microorganisms
and accelerate those microbial processes which augment the availability of
nutrients that can be easily assimilated by plants.
• Biofertilizers are biologically active products, with the ability to provide plants
with nutrients and may be nitrogen fixers, phosphorus solubilizers, sulphur
oxidisers or organic matter decomposers. In short, they are called as bioinoculants
which on supply to plants improve their growth and yield.
• They are being essential component of organic farming.
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 Types of Biofertilizers

• Most biofertilizers belong to one of two categories: nitrogen fixing and phosphate
solubilising.
1. Nitrogen fixing biofertilizers: Nitrogen fixing biofertilizers fix atmospheric
nitrogen into forms which are readily useable by plants. These include Rhizobium,
Azotobacter and Azospirillum, Blue Green Algae (BGA) and Azolla.
• While Rhizobium requires symbiotic association with the root nodules of legumes
to fix nitrogen, others can fix nitrogen independently.
2. Phosphate solubilising micro-organisms: Phosphate solubilising micro-
organisms such as Bacillus, Pseudomonas, Aspergillus etc. secrete organic acids
which enhance the uptake of phosphorus by plants by dissolving rock phosphate.
• Some others are phosphate mobilizers and zinc solubilizers.

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 Advantages of Biofertilizers

• Renewable source of nutrients.

• Sustain soil health and increase the grain yields by 10-40%
• Supplement chemical fertilizers and replace 25-30% chemical fertilizers,
• Decompose plant residues, and stabilize C: N ratio of soil.
• Improve texture, structure and water holding capacity of soil.
• Stimulates plant growth by secreting growth hormones and has no adverse effect
on plant growth and soil fertility.
• Solubilize and mobilize nutrients.
• Eco-friendly, non-pollutant and cost effective method.

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 Limitations of biofertilizers

• Non availability of appropriate and efficient strains of bacteria.

• Lack of suitable carrier, due to which self life is short, is another constraint.
• Marketing of biofertilizer is not easy as the product contains living organisms.
• Seasonal demand and production of biofertilizers.
• Scarcity and viability of vesicular Arbuscular Mycorrhizal (VAM) inoculum
during storage and transportation is the major problem.
• Lack of awareness of farmers.
• Inadequate and inexperienced staff.
VAM is a fungus which has the ability to dissolve the phosphates found in
abundance in the soil.

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 Biopesticides and Bio-control Agents

• Biopesticides are a vital component of sustainable agriculture.

• Biopesticides are derived from natural materials such as animals, plants, bacteria,
and certain minerals widely used for controlling insects and disease causing
pathogens.
• The biopesticides are categorized under microbial pesticides, plant-incorporated-
protectants and biochemical pesticides, which are produced through naturally
occurring substances that control pests by non-toxic mechanisms.
• Biopesticides are usually inherently less toxic; generally affect only the target pest,
effective in very small quantities, easily biodegradable, thereby resulting in lower
exposures and largely avoiding the pollution problems.

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 Classes of Biopesticides
• Biopesticides fall into three major classes:
1. Microbial pesticides: Microbial pesticides consist of a microorganism (e.g., a
bacterium, fungus, virus or protozoan) as the active ingredient. Microbial pesticides
can control many different kinds of pests, although each separate active ingredient is
relatively specific for its target pest[s]. For example, there are fungi that control
certain weeds, and other fungi that kill specific insects. The most widely used
microbial pesticides are subspecies and strains of Bacillus thuringiensis, or Bt. Each
strain of this bacterium produces a different mix of proteins, and specifically kills
one or a few related species of insect larvae. While some Bt’s control moth larvae
found on plants, other Bt’s are specific for larvae of flies and mosquitoes.
2. Plant-Incorporated Protectants (PIPs): PIPs are pesticidal substances that
plants produce from genetic material that has been added to the plant. For example,
scientists can take the gene for the Bt. pesticidal protein, and introduce the gene into
the plant's own genetic material. Then the plant, instead of the Bt. bacterium,
manufactures the substance that destroys the pest.
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 Classes of Biopesticides

3. Biochemical/ herbal
pesticides: Biochemical
pesticides are naturally
occurring substances that
control pests by non-toxic
mechanisms. Biochemical
pesticides include
substances, such as insect
sex pheromones that
interfere with mating as
well as various scented
plant extracts that attract
insect pests to traps.

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 The Advantages of Biopesticides

• Biopesticides are usually inherently less toxic than conventional pesticides.

• Biopesticides generally affect only the target pest and closely related organisms.

• Biopesticides often are effective in very small quantities and often decompose
quickly, thereby resulting in lower exposures and largely avoiding the pollution
Problems.

• When used as a component of Integrated Pest Management (IPM) programs,

biopesticides can greatly decrease the use of conventional pesticides, while crop
yields remain high.

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 Disadvantages of Biopesticides

• Instability of the protection effect.

• Limited period of activity.
• Biopesticides are usually are used with normal pesticide application techniques.
• Difficulty in establishment of the biopesticide agents in the fields.
• Ambiguity of modes of protection.
• Low potency.
• High cost of production.

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 Difference Biopesticides and Chemical Pesticides

Biopesticides Chemical Pesticides

Friendly to non-target species Harmful to non-target species

Do not cause pollution Serious pollution to the environment

Relatively cheaper Relatively expensive

Pests never develop resistance Pests eventually become resistant

Growing market preference Diminishing market

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