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Those microbes, plants and animals which cause harm to crop or their products are called pests. Viruses bacteria Fungi, insects or big animals may also be a pest. Those biological factors used to kill insects, weeds and pests and pathogens are called Biopesticides. Certain viruses, bacteria, fungi and protozoa are used as biopesticides.

Bacillus thermogenesis is a soil-inhabiting bacterium. It is Grampositive and spores of this bacterium produce a pesticide, crystal protein. These spores are being used to kill the eggs of certain insects. The first pesticide at commercial level was made from this Bacterium.

Biofertilizers:

• These days, scientists are cultivating the microbes which can fix atmospheric nitrogen at commercial scale. The microbes which enrich the soil in nutrients by their biological activities are called as biofertilizers.
• The biofertilizers also accelerate the process of mineralization, in addition, to the increase in soil fertility.
• Some of the examples of biofertilizers are Bacteria, Cyanobacteria, Fungi etc. 

These biofertilizers are mainly of six types: 

1. Symbiotic bacterium – Rhizobium: 

• These bacteria are found in the root nodules of leguminous plants and obtain nutrition from the plant. They fix (trap) atmospheric nitrogen and convert it into ammonia and liberate it outside, which in turn is consumed by the plant.
• Rhizobium can fix atmospheric nitrogen at a rate of 50 to 150 kg per hectare per year.
• The use of these bacteria as biofertilizer can increase production up to 15 – 20%. Even the next crop grown after its application will yield more because of increased soil fertility. 

2. Non-symbiotic Bacteria: 

• Non-symbiotic bacteria such as Azotobactor, Azospirillum, Clostridium etc. can also fix the nitrogen present in the soil and make it available to the plant. These bacteria absorb the free nitrogen of soil and convert it into organic nitrogenous compounds.
• After the death of these bacteria, the nitrogenous compounds contained in these are decomposed by decomposing bacteria and the ammonia is released. The released ammonia is converted into nitrite and finally into nitrate which is finally used by the plants.
• Azotobactor is used as biofertilizer during rice, maize, cotton cultivation. The production is increased up to 20%. 

3. Blue-Green Algae or Cyanobacteria:

• Cyanobacteria such as Anabaena, Nostoc, Plectonema and other non-symbiotic prokaryotes perform nitrogen fixation. 
• Cyanobacteria have special cells called heterocyst. The Nif gene present in these cells does nitrogen fixation. 
• Rice fields are ideal for the growth of blue-green algae, hence use of blue-green algae in paddy fields increases the production of rice. Nowadays, one aquatic pteridophyte called Azolla is also used along with blue-green algae as algal biofertilizer in Southern and South-East Asia. 
• The Azolla is a floating aquatic fern. Leaves of Azolla contain blue-green algae Anaebaen Azolla which fixes atmospheric nitrogen. Anabaena pinata is also a good biofertilizer. When it is used in combination with Azolla, it can increase rice production by 50%.
• Anabaena Azolla is commercially produced at Central Rice Research Institute, Cuttack. 

4. Mycorrhiza: Symbiotic association of fungi with roots of higher plants is called Mycorrhiza. The fungus absorbs nutrients from the soil and provides to host plant and in turn host plant provides nutrition to the fungus. 

5. Phosphate dissolving Bacteria: Some bacteria such as Pseudomonas, Microbacterium, Bacillus etc. Convert non-available inorganic phosphate into available organic phosphate which is easily absorbed by plants. 

6. Organic manure: In India organic waste products are available in large amount in the form of domestic wastes, urban waste, sewage, remains of crops, animal excreta, bone powder etc. These wastes can be converted into organic manure by microbial degradation and can be used by plants.

Blue-Green Algae or Cyanobacteria: 

• Cyanobacteria such as Anabaena, Nostoc, Plectonema and other non-symbiotic prokaryotes perform nitrogen fixation.
• Cyanobacteria have special cells called heterocyst. The Nif gene present in these cells does nitrogen fixation. 
• Rice fields are ideal for the growth of blue-green algae, hence use of blue-green algae in paddy fields increases the production of rice. Nowadays, one aquatic pteridophyte called Azolla is also used along with blue-green algae as algal biofertilizer in Southern and South-East Asia. 
• The Azolla is a floating aquatic fern. Leaves of Azolla contain blue-green algae Anaebaen Azolla which fixes atmospheric nitrogen. Anabaena pinata is also a good biofertilizer. When it is used in combination with Azolla, it can increase rice production by 50%.
• Anabaena Azolla is commercially produced at Central Rice Research Institute, Cuttack.

The answer is Azotobactor, Azospirilum

The answer is (b) Nostoc

The answer is (c) Nostoc

The answer is Central Rice Research Institute, Cuttack

The answer is (c) Rhizobium

The answer is Pseudomonas.

The answer is Bacillusthuringiensis

The answer is Biofertilizers.

The answer is Pests

The answer is (b) Condensed (Compact) agriculture

1. Chemical fertilizer 

2. Pesticides

The answer is (a) Biopesticides

• Symbiotic association of fungi with roots of higher plants is called Mycorrhiza.
• The fungus absorbs nutrients from the soil and provides to host plant and in turn host plant provides nutrition to the fungus.

Aims of Organic Agriculture: 

• To increase the soil fertility and to ensure its continuity for long. 
• It results in increased metabolic activities of microbes, soil organisms, plants and organisms related to the agricultural process.
• Eco-friendly use of the natural ecosystem.
• Promotes the use of local agricultural practices and alternative sources of energy in agriculture.
• Increase in production of food with high nutritious values. 
• Prevents pollution by use of new technology related to agriculture.

• Cyanobacteria such as Anabaena, Nostoc, Plectonema and other procaryotic non-symbiotic organisms are involved in atmospheric nitrogen fixation. Blue-green algae have a very special cell called as Heterocyst. 
• Nif gene present in heterocyst does the nitrogen fixation. An environment of Rice field is ideal for the growth of blue-green algae: Use of blue-green algae in paddy fields increases production

The answer is Organic farming

In ancient time, the three basic needs of human being namely food, cloth and shelter were fulfilled using the plants. However, as time passed away the human requirements increased many folds. The population explosion, industrial revolution and development of transport facilities created tremendous pressure on the natural resources and some of them are depleting at an alarming rate. 

If this situation continues, the future generation will have to suffer for lack of resources. There may be a lack of fresh air for breathing, pure and potable water for drinking and lack of nutritive food. Now, we have started thinking globally that how the present human needs are fulfilled without creating an imbalance in nature and without compromising the needs of the further generation. Looking into this context, the concept of sustainable agriculture has developed.

Sustainable agriculture is an integrated system of practices of cultivation of agricultural plants and livestock in which cultivation site can be maintained for a long period of time without any harm, and human requirements can be fulfilled for a long time.

• These days, scientists are cultivating the microbes which can fix atmospheric nitrogen at commercial scale. The microbes which enrich the soil in nutrients by their biological activities are called as biofertilizers.
• The biofertilizers also accelerate the process of mineralization, in addition, to an increase in soil fertility.
• Some of the examples of biofertilizers are Bacteria, Cyanobacteria, Fungi etc.

Economic & Ecological Importance of Organic Agriculture: 

• It is a very simple and cheap technique, hence can be adopted by even small farmer.
• Use of biofertilizers increases water holding capacity and aeration of the soil.
• Temperature and pH of the soil are maintained by use of biofertilizers as a result bacteria in the soil remain functional.
• By organic farming, the toxicity of soil is reduced and ecological balance is maintained.
• By use of biofertilizers, we can convert barren land into fertile land. Degradation of the biofertilizers produces organic acids which reduce soil alkalinity.
• It is pollution-free and maintains soil fertility. 
• Soil erosion can be prevented by organic agriculture. 
• The biofertilizers release a balanced amount of nutrients and thus leads to increased fertility of the soil. 
• Soil fertility is maintained for years by organic farming and leads to an increase in yield for a long duration. 
• Cost of crop production is reduced by the use of biofertilizers and ultimately leads to economic profit.