Biofertilizer Questions in English

(A) Biofertilizers are organisms that enrich the nutrient quality of the soil.
Blue-green algae (cyanobacteria) are autotrophic microbes widely distributed in aquatic and terrestrial environments,many of which can fix atmospheric nitrogen,thereby increasing the nitrogen content of the soil and enhancing its fertility.
Bt-cotton is a genetically modified crop resistant to pests,not a biofertilizer.
Saccharomyces cerevisiae (yeast) is primarily used in the baking and brewing industries.
Therefore,blue-green algae are the correct organisms used as biofertilizers.

(A) $Bacillus \text{ } thuringiensis$ is a bacterium that produces a toxic insecticidal protein. It is widely used as a bio-pesticide or bio-control agent to control insect pests, not as a bio-fertilizer.
$Azospirillum$, $Azotobacter$, and $Rhizobium$ are well-known bio-fertilizers that fix atmospheric nitrogen in the soil, thereby increasing soil fertility.

(D) Organic fertilizers or biofertilizers are organisms that enrich the nutrient quality of the soil.
$1$. Bacteria (e.g.,$Rhizobium$,$Azospirillum$) fix atmospheric nitrogen.
$2$. Cyanobacteria (e.g.,$Anabaena$,$Nostoc$) are autotrophic microbes widely used in paddy fields to fix nitrogen and add organic matter.
$3$. Fungi (e.g.,$Mycorrhiza$) form symbiotic associations with roots to help in phosphorus absorption.
Since all these groups are used as biofertilizers,the correct answer is $D$.

(A) The correct answer is $Azospirillum$.
$Azospirillum$ is a genus of Gram-negative,nitrogen-fixing bacteria that live in association with the roots of various grasses and cereal crops,acting as a biofertilizer.
$Ladybird$ is a beetle used as a biocontrol agent for aphids.
$Aphids$ are insects that act as pests on plants.
$Monascus$ is a genus of fungi used in the production of statins.

(D) The cyanobacterium $Anabaena$ $azollae$ is a nitrogen-fixing organism that lives in a symbiotic association with the water fern $Azolla$.
It resides within the leaf cavities of $Azolla$,providing fixed nitrogen to the plant in exchange for carbohydrates and a protected environment.
This association is widely used as a biofertilizer in rice cultivation.

(B) $Azotobacter$ is a free-living nitrogen-fixing bacterium that lives in the soil and fixes atmospheric nitrogen.
$VAM$ (Vesicular-Arbuscular Mycorrhiza) is a symbiotic fungus.
$Anabaena$ is a cyanobacterium that can be free-living or symbiotic (e.g.,in $Azolla$).
$Rhizobium$ is a symbiotic bacterium that forms nodules in the roots of leguminous plants.
Therefore,$Azotobacter$ is the correct example of a free-living biofertilizer.

(B) $Azolla$ $pinnata$ is a small aquatic fern that has a symbiotic relationship with the nitrogen-fixing cyanobacterium $Anabaena$ $azollae$.
This fern is widely used as a biofertilizer in rice fields because it fixes atmospheric nitrogen and provides it to the rice plants.
Studies have shown that the use of $Azolla$ can increase rice production by more than $50\%$ due to the enrichment of soil nitrogen content.

(A) $Azolla$ is a small aquatic fern that has a symbiotic relationship with the nitrogen-fixing cyanobacterium $Anabaena$ $azollae$.
This association allows $Azolla$ to fix atmospheric nitrogen,making it an excellent biofertilizer for rice paddies.
It is widely used in agriculture to increase soil fertility naturally.

(B) Organic farming relies on the use of biofertilizers and biological control agents to maintain soil fertility and manage pests.
$Oscillatoria$ is a cyanobacterium that acts as a biofertilizer by fixing atmospheric nitrogen.
$Glomus$ is a genus of arbuscular mycorrhizal fungi that helps plants absorb phosphorus from the soil.
Earthworms are known as 'farmers' friends' as they improve soil aeration and fertility through vermicomposting.
Snails are generally considered garden pests that consume crops and are not used as biofertilizers or beneficial agents in organic farming.

(C) Paddy fields (rice fields) are waterlogged environments where cyanobacteria like $Anabaena$ and $Oscillatoria$ act as biofertilizers by fixing atmospheric nitrogen.
$Oscillatoria$ is a genus of filamentous cyanobacteria that is commonly found in paddy fields and contributes to nitrogen fixation,thereby increasing soil fertility.

(B) Soybean is a leguminous plant.
$Rhizobium$ is a symbiotic nitrogen-fixing bacterium that forms root nodules in leguminous plants.
It fixes atmospheric nitrogen into ammonia,which is then utilized by the plant for growth,thereby increasing the crop yield.
Therefore,$Rhizobium$ is used as a biofertilizer for soybean crops.

(B) The aquatic fern $Azolla$ lives in a symbiotic relationship with the cyanobacterium $Anabaena$ $azollae$.
This cyanobacterium resides in the leaf cavities of $Azolla$.
It fixes atmospheric nitrogen and provides it to the fern,while the fern provides shelter and nutrients to the cyanobacterium.
This association is widely used as a biofertilizer in paddy fields to enhance nitrogen content in the soil.

(C) Many members of the genus $Glomus$ form symbiotic associations with plants,which are known as mycorrhiza. In this association,the fungal symbiont absorbs phosphorus from the soil and passes it to the plant. Plants having such associations show other benefits like resistance to root-borne pathogens,tolerance to salinity and drought,and an overall increase in plant growth and development. Therefore,$Glomus$ acts as a biofertilizer.

(A) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$Azolla$ is a water fern that has a symbiotic relationship with the cyanobacterium $Anabaena azollae$,which fixes atmospheric nitrogen.
$BGA$ (Blue-Green Algae),such as $Nostoc$ and $Anabaena$,are also well-known biofertilizers that fix nitrogen and increase soil fertility.
Therefore,$Azolla$ and $BGA$ represent a correct pair of biofertilizers.

(C) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$Rhizobium$ is a symbiotic nitrogen-fixing bacterium that forms nodules in the roots of leguminous plants.
Cyanobacteria (such as $Anabaena$ and $Nostoc$) are autotrophic microbes that fix atmospheric nitrogen in paddy fields and other environments.
Both $Rhizobium$ and Cyanobacteria are widely used as biofertilizers in agriculture to enhance crop yield.
$Aspergillus$ and $Rhizopus$ are fungi that are generally not used as biofertilizers; $Aspergillus$ is often used in industrial production of enzymes or organic acids,and $Rhizopus$ is a common bread mold.

(N/A) Single Cell Protein $(SCP)$
Single Cell Protein $(SCP)$ refers to protein extracted from pure or mixed cultures of algae,yeasts,fungi,or bacteria,which serves as an alternative protein source for human food or animal feed. Microbes like $Spirulina$ are grown on industrial scales using waste materials such as molasses,sewage,and animal manure. $SCP$ is a rich source of proteins,carbohydrates,fats,minerals,and vitamins. Additionally,microorganisms like $Methylophilus$ $methylotrophus$ have a high rate of biomass production,making them efficient for large-scale protein synthesis.
$(b)$ Soil
Microbes are essential for maintaining soil fertility. They contribute to the formation of nutrient-rich humus through the decomposition of organic matter. Many bacteria and cyanobacteria are capable of fixing atmospheric nitrogen into forms usable by plants. $Rhizobium$ is a symbiotic bacterium found in the root nodules of leguminous plants. $Azospirillum$ and $Azotobacter$ are free-living nitrogen-fixing bacteria,while $Anabaena$,$Nostoc$,and $Oscillatoria$ are examples of nitrogen-fixing cyanobacteria.

(N/A) Bio-fertilizers are living organisms that help in increasing the fertility of the soil.
They involve the selection of beneficial microorganisms that improve plant growth by supplying essential nutrients.
These organisms are introduced to seeds,roots,or soil to mobilize nutrient availability through their biological activity.
They enrich the soil with organic nutrients,making them highly beneficial.
Many species of bacteria and cyanobacteria have the ability to fix free atmospheric nitrogen.
$Rhizobium$ is a symbiotic bacterium found in the root nodules of leguminous plants.
$Azospirillum$ and $Azotobacter$ are free-living nitrogen-fixing bacteria,whereas $Anabaena$,$Nostoc$,and $Oscillatoria$ are examples of nitrogen-fixing cyanobacteria.
Bio-fertilizers are cost-effective and eco-friendly alternatives to chemical fertilizers.

(A) Environmental pollution is a major cause of concern. The use of chemical fertilisers to meet the ever-increasing demand for agricultural produce has contributed significantly to this pollution.
There are problems associated with the overuse of chemical fertilisers,and there is significant pressure to switch to organic farming.
Biofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria,fungi,and cyanobacteria.
$1$. Bacteria: The nodules on the roots of leguminous plants are formed by the symbiotic association of $Rhizobium$. These bacteria fix atmospheric nitrogen into organic forms,which are used by the plant as nutrients. Other bacteria,such as $Azospirillum$ and $Azotobacter$,can fix atmospheric nitrogen while living freely in the soil,thus enriching the nitrogen content.
$2$. Fungi: Many fungi form symbiotic associations with plants known as mycorrhiza (e.g.,genus $Glomus$). The fungal symbiont absorbs phosphorus from the soil and passes it to the plant. These associations also provide resistance to root-borne pathogens,tolerance to salinity and drought,and promote overall plant growth and development.
$3$. Cyanobacteria: These are autotrophic microbes that fix atmospheric nitrogen (e.g.,$Anabaena$,$Nostoc$,$Oscillatoria$). In paddy fields,they serve as important biofertilisers,adding organic matter to the soil and increasing its fertility.
Currently,many biofertilisers are available commercially,helping farmers reduce their dependence on chemical fertilisers.

(N/A)

Chemical Fertilizer	Biofertilizer
$(1)$ These are synthetic substances containing specific chemical compounds.	$(1)$ These are living organisms like bacteria,fungi,or cyanobacteria.
$(2)$ Excessive use leads to soil degradation and water pollution.	$(2)$ They enrich the soil nutrient quality and are eco-friendly.
$(3)$ They provide nutrients like $N$,$P$,and $K$ directly.	$(3)$ They fix atmospheric nitrogen or solubilize phosphorus biologically.
$(4)$ They are harmful to the long-term health of the environment.	$(4)$ They are beneficial for sustainable agriculture and environment.

(N/A) $1$. To meet the increasing demand for agricultural products,the use of chemical fertilizers has risen significantly.
$2$. Chemical fertilizers are a major source of environmental pollution,contaminating soil and water bodies.
$3$. These chemicals are harmful to the health of living organisms,including humans,as they can enter the food chain.
$4$. Biofertilizers,on the other hand,enrich the soil with nutrients naturally,improve soil structure,and are eco-friendly.
$5$. Consequently,there is a growing global shift and pressure toward adopting organic farming and biofertilizers to ensure sustainable agriculture and public health.

(A) Biofertilizers are organisms that enrich the nutrient quality of the soil.
These include bacteria,fungi,and cyanobacteria.
They fix atmospheric nitrogen,solubilize phosphorus,or produce plant growth-promoting substances,thereby enhancing soil fertility naturally.

(N/A) Organic farming is a method of farming that primarily aims at cultivating the land and raising crops in such a way,as to keep the soil alive and in good health by use of organic wastes (crop,animal and farm wastes,aquatic wastes like algae) and other biological materials along with beneficial microbes (biofertilizers) instead of chemical fertilizers.
Benefits of organic farming include:
$1$. Sustainability: It maintains soil fertility and ecological balance,ensuring long-term agricultural productivity.
$2$. Environmental Protection: It reduces pollution by eliminating the use of synthetic chemical fertilizers and pesticides,which often contaminate groundwater and soil.
$3$. Soil Health: It improves soil structure,water-holding capacity,and nutrient content through the addition of organic matter (compost/manure).
$4$. Biodiversity: It promotes a healthy ecosystem by supporting a variety of beneficial insects,microorganisms,and plants,which helps in natural pest control.
$5$. Healthier Produce: Organic crops are free from toxic chemical residues,making them safer and healthier for human consumption.

(B) Blue-green algae (cyanobacteria) are not widely popular as biofertilisers because they can cause algal blooms in polluted water bodies,leading to eutrophication.
While they are excellent nitrogen fixers,their tendency to overgrow in nutrient-rich water makes them problematic in certain ecological contexts.
Only those blue-green algae that contain specialized cells called heterocysts are capable of $N_{2}$ fixation.

(B) Mycorrhizal fungi,such as those in the genus $Glomus$,form a symbiotic association with plant roots.
They absorb phosphorus from the soil and transfer it to the host plant cells.
Additionally,they provide resistance to the host plant against root-borne pathogens.
They also increase the plant's tolerance to salinity and drought conditions.

(A) Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments,many of which can fix atmospheric nitrogen (they contain specialized cells called heterocysts),e.g.,$Anabaena$,$Nostoc$,$Oscillatoria$,etc.
In paddy fields,cyanobacteria serve as an important biofertiliser and increase crop yield by up to $50 \%$.
Blue-green algae also add organic matter to the soil,which improves soil structure and increases its overall fertility.

(N/A) Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria,fungi,and cyanobacteria.
Examples:
$(i)$ $Rhizobium$,$Azospirillum$,and $Azotobacter$ are bacteria that fix atmospheric nitrogen in the soil.
$(ii)$ $Anabaena$,$Nostoc$,and $Oscillatoria$ (Blue-Green Algae) are used as biofertilizers to add organic matter and nitrogen to the soil.

(B) Ramesh Chandra Dagar is a farmer from Sonipat,Haryana. He is known for his contribution to organic farming. He developed a method of integrated organic farming,which includes bee-keeping,dairy management,water harvesting,composting,and agriculture in a chain-like process. He utilizes animal waste (manure) as a natural fertilizer instead of chemical fertilizers,ensuring that waste from one process is used as a nutrient for another.

(N/A) Organic farming is an agricultural system that uses biofertilisers,organic manure,and biological pest control instead of synthetic chemical fertilisers and pesticides.
Biofertilisers are organisms that enrich the nutrient quality of the soil.
- The main sources of biofertilisers are bacteria,fungi,and cyanobacteria.
- The nodules on the roots of leguminous plants are formed by the symbiotic association of $Rhizobium$. These bacteria fix atmospheric nitrogen into organic forms,which are used by the plant as nutrients.
- Other bacteria can fix atmospheric nitrogen while free-living in the soil (examples: $Azospirillum$ and $Azotobacter$),thus enriching the nitrogen content of the soil.
Currently,in our country,a number of biofertilisers are available commercially,and farmers use these regularly to replenish soil nutrients.
Benefits of organic farming:
$(i)$ Soil fertility is maintained for a long period.
$(ii)$ Water quality is preserved by reducing chemical runoff.
$(iii)$ It is an economical option as farmers do not need to spend money on expensive chemical pesticides and insecticides.
$(iv)$ It promotes the production of nutritious,high-quality crops free from toxic chemical residues.

(N/A) Integrated organic farming is a cyclical,zero-waste procedure in which waste products from one process are cycled in as nutrients for other processes to allow the maximum utilization of resources and increase the efficiency of production.
Ramesh Chandra Dagar,a farmer in Sonipat,Haryana,created the Haryana Kisan Welfare Club,which currently has a membership of $5000$ farmers.
This club promotes integrated organic farming,which includes bee-keeping,dairy management,water harvesting,composting,and agriculture in a chain of processes that support each other,allowing for an extremely economical and sustainable venture.
Crop waste is used to create compost,which serves as a natural fertilizer or is used to generate biogas to satisfy the energy needs of the farm.

(C) Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria,fungi,and cyanobacteria.
$1$. Bacteria: Examples include $Rhizobium$,$Azospirillum$,and $Azotobacter$,which fix atmospheric nitrogen.
$2$. Fungi: Mycorrhiza (e.g.,$Glomus$) absorbs phosphorus from the soil and passes it to the plant.
$3$. Cyanobacteria: Examples include $Anabaena$,$Nostoc$,and $Oscillatoria$,which are autotrophic microbes that fix atmospheric nitrogen,especially in paddy fields.
Protozoa are generally heterotrophic organisms that feed on bacteria and organic matter; they do not act as biofertilizers in agricultural practices. Therefore,the correct answer is $C$.

(D) $Glomus$ is a genus of arbuscular mycorrhizal fungi $(AMF)$.
These fungi form a symbiotic association with the roots of higher plants.
The fungal hyphae penetrate the root cells and extend into the soil,significantly increasing the surface area for nutrient absorption.
The primary function of this symbiotic association is the absorption of phosphorus from the soil and its transfer to the plant.
Therefore,the correct option is $D$.

(B) Mycorrhiza is a symbiotic association between a fungus and the roots of higher plants.
Many members of the genus $Glomus$ form mycorrhiza.
The fungal symbiont in these associations absorbs phosphorus from the soil and passes it to the plant.
Plants having such associations show other benefits also,such as resistance to root-borne pathogens,tolerance to salinity and drought,and an overall increase in plant growth and development.
Therefore,$Glomus$ is the correct option.

(A) Cyanobacteria,such as $Anabaena$ and $Nostoc$,are commonly used as biofertilizers in paddy fields.
They are capable of fixing atmospheric nitrogen,which enriches the soil with nitrogenous compounds.
$Anabaena$ is often found in the leaf cavities of the water fern $Azolla$,which is grown in rice fields to provide nitrogen to the crop.

(C) Blue-green algae (Cyanobacteria) are autotrophic microbes that are widely distributed in aquatic and terrestrial environments. Many of these,such as $Anabaena$ and $Nostoc$,have the ability to fix atmospheric nitrogen into organic forms,which is then utilized by plants. By adding nitrogenous compounds to the soil,they significantly enhance soil fertility and act as natural biofertilizers.

(B) Azospirillum is a free-living nitrogen-fixing bacterium,so $a-2$.
$(b)$ Cyanobacteria (like Anabaena,Nostoc) are autotrophic microbes that fix nitrogen,so $b-4$.
$(c)$ Rhizobium is a symbiotic bacterium found in the root nodules of legumes,so $c-1$.
$(d)$ Glomus is a fungal genus that forms symbiotic associations with plants known as mycorrhiza,so $d-3$.
Therefore,the correct matching is $a-2, b-4, c-1, d-3$.

(D) $Azolla$ is a pteridophyte and it is used as a biofertiliser because it has a symbiotic association with nitrogen-fixing cyanobacteria called $Anabaena \ azollae$.

(A) Lichens are symbiotic associations between fungi (mycobiont) and algae or cyanobacteria (phycobiont).
Azotodesmic lichens are specific types of lichens that contain nitrogen-fixing cyanobacteria (such as Nostoc or Anabaena) as their phycobiont component.
These cyanobacteria possess specialized cells called heterocysts,which are the sites of nitrogen fixation.
By fixing atmospheric nitrogen into ammonia,these lichens enrich the soil with nitrogen,acting as natural biofertilisers.
Therefore,both the Assertion and the Reason are correct,and the Reason provides the correct explanation for the Assertion.

(B) $VAM$ stands for Vesicular-Arbuscular Mycorrhizae.
It is a type of endomycorrhizae where the fungal hyphae penetrate the cortical cells of the roots of the host plant.
These fungi form specialized structures called vesicles (for storage) and arbuscules (for nutrient exchange) within the root cells.
They are commonly used as biofertilizers in various crops such as cereals,pulses,oilseeds,and fruit crops to enhance phosphorus uptake.

(D) Azolla is a small aquatic fern that is cultivated in rice fields because it provides both green manure and fixed nitrogen to the crop.
It contains a symbiotic cyanobacterium, $Anabaena \ azollae$, in its leaves which fixes atmospheric nitrogen.
The use of Azolla in rice fields at the rate of $200 \ g$ per square metre can increase rice yield by $12.38 \ \%$.
Experiments have revealed that the application of $10$ tonnes of fresh Azolla biomass per hectare adds approximately $100 \ kg$ of nitrogen to the soil.

(D) Biofertilisers are organisms that enrich the nutrient quality of the soil.
$1$. Bacteria: Many bacteria like $Rhizobium$ and $Azospirillum$ fix atmospheric nitrogen into organic forms, which are used by plants as nutrients.
$2$. Cyanobacteria: These are autotrophic microbes (e.g., $Anabaena$, $Nostoc$) that fix atmospheric nitrogen and also add organic matter to the soil, increasing its fertility.
$3$. Fungi: Many fungi form symbiotic associations with the roots of higher plants, known as $Mycorrhiza$ (e.g., $Glomus$). These fungi absorb phosphorus from the soil and pass it to the plant, while also providing resistance to root-borne pathogens and increasing tolerance to salinity and drought.
Since all three groups contribute to soil fertility, the correct answer is $\text{All of these}$.

(C) Azospirillum is a Gram-negative,free-living bacterium that absorbs free nitrogen from the soil and air,converting it into nitrogenous compounds like amino acids,thereby enriching soil nutrients.
Nostoc,Anabaena,and Oscillatoria are cyanobacteria that fix atmospheric nitrogen and increase the organic matter content of the soil through their photosynthetic activity.
All four organisms mentioned are prokaryotic in nature and are capable of fixing atmospheric nitrogen. Therefore,both $(a)$ and $(b)$ are correct.

(D) Cyanobacteria like $Nostoc$ and $Anabaena$ are widely used as biofertilizers in paddy fields.
They are capable of fixing atmospheric nitrogen into ammonia,which enriches the soil with nitrogenous nutrients.
Additionally,they contribute to the organic matter content of the soil through their photosynthetic activity,thereby enhancing soil fertility.

(B) Biofertilisers are organisms that enrich the nutrient quality of the soil.
$I.$ Cyanobacteria (blue-green algae) like $Nostoc$ and $Anabaena$ are widely used as biofertilisers,especially in paddy fields,as they fix atmospheric nitrogen.
$II.$ Yeast is a fungus used in fermentation processes (e.g.,brewing and baking) but is not a biofertiliser.
$III.$ Symbiotic bacteria like $Rhizobium$ live in the root nodules of leguminous plants and fix atmospheric nitrogen.
$IV.$ Free-living bacteria like $Azospirillum$ and $Azotobacter$ live in the soil and fix atmospheric nitrogen,thereby enriching the soil with nitrogenous compounds.
Therefore,$I, III,$ and $IV$ are used as biofertilisers.

(D) Biofertilisers are organisms that enrich the nutrient quality of the soil.
Bacteria,fungi,and cyanobacteria are the three main sources of biofertilisers.
Therefore,all of these organisms are used to enrich the soil nutrient quality.

(C) The leaves of Azolla (a water fern) contain cavities that harbor the nitrogen-fixing cyanobacterium $Anabaena \ azollae$.
This symbiotic association allows the fern to fix atmospheric nitrogen,which is then made available to the plant and the soil.
$Azolla \ pinnata$ is widely used as an excellent biofertilizer,particularly in rice cultivation.
Farmers have reported up to a $50 \%$ increase in rice yield by using this biofertilizer.

(A) The Neem tree $(Azadirachta \text{ } indica)$ is of significant industrial importance.
It produces compounds like azadirachtin, meliantriol, and salannin, which act as effective biopesticides (insect repellents and antifeedants).
Additionally, neem extracts are researched and used for their anti-fertility properties.
Neem cake is also widely used as a biofertilizer to improve soil fertility.
Therefore, it serves as a source of biofertilizer, biopesticide, and anti-fertility compounds.