Biofertilizer Questions in English

(D) Green manure refers to crops grown specifically to be incorporated into the soil while still green or shortly after flowering.
$1$. It adds significant amounts of organic matter to the soil,which improves soil structure and water-holding capacity.
$2$. Leguminous green manure crops fix atmospheric nitrogen,thereby providing additional nitrogen to the soil.
$3$. By covering the soil surface,green manure crops protect the soil from erosion caused by wind or water and reduce nutrient leaching.
Therefore,all the given options are correct.

(C) Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria,fungi,and cyanobacteria. The use of biofertilizers is known to increase crop productivity by approximately $15-20\%$. Among the given options,$10-20\%$ is the most accurate range.

(B) $Azolla$ $pinnata$ is an aquatic fern that maintains a symbiotic relationship with the nitrogen-fixing cyanobacterium $Anabaena$ $azollae$.
This cyanobacterium resides in the leaf cavities of the fern and fixes atmospheric nitrogen,which makes $Azolla$ an excellent biofertilizer,particularly in rice cultivation.
It enriches the soil with nitrogen and improves crop yield.

(D) $BGA$ (Blue-Green Algae),such as $Anabaena$ and $Nostoc$,are prokaryotic organisms capable of fixing atmospheric nitrogen.
They are extensively used as biofertilizers in paddy (rice) fields.
Paddy fields provide an ideal environment for the growth of $BGA$ due to the presence of standing water and high humidity.
The $BGA$ adds organic matter to the soil and increases the nitrogen content,which significantly promotes the growth of the paddy crop.

(D) The statement 'Nowadays,the use of pesticides is mainly natural' is incorrect. In modern agriculture,the use of synthetic chemical pesticides is widespread,which often leads to environmental pollution and health hazards. While there is a growing trend towards organic farming and biopesticides,it is not yet the primary or 'natural' method used globally. Biofertilizers (Option $A$) are indeed used to enrich soil nutrients,chemical fertilizers (Option $B$) are known pollutants,and chemical fertilizers (Option $C$) are generally more expensive than organic alternatives.

(C) Azolla is a small aquatic fern (pteridophyte) that lives in a symbiotic relationship with the nitrogen-fixing cyanobacterium $Anabaena$ $azollae$.
This cyanobacterium resides in the leaf cavities of $Azolla$.
Because $Anabaena$ fixes atmospheric nitrogen into ammonia,it enriches the soil with nitrogen when $Azolla$ decomposes in rice fields.
Therefore,$Azolla$ acts as a biofertilizer,significantly increasing the yield of rice crops.

(A) The cyanobacterium $Anabaena$ $azollae$ lives in a symbiotic association with the aquatic fern $Azolla$.
It resides in the leaf cavities of $Azolla$ and fixes atmospheric nitrogen,which is then utilized by the fern.
This relationship is highly beneficial for rice cultivation,as $Azolla$ is often used as a biofertilizer in paddy fields.

(A) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$Azolla$ is a small aquatic fern that has a symbiotic relationship with the cyanobacterium $Anabaena$ $azollae$ (a type of $BGA$ or Blue-Green Algae).
This association helps in nitrogen fixation,making $Azolla$ and $BGA$ a correct pair for biofertilizers.
$Rhizobium$ forms a symbiotic association with leguminous plants,not grass.
$Nostoc$ can fix nitrogen,but it is not typically paired with legumes as a primary biofertilizer source in this context.
$Salmonella$ and $E. coli$ are generally pathogenic or commensal bacteria,not biofertilizers.

(A) Many members of the genus $Glomus$ form mycorrhiza,which is a symbiotic association between a fungus and the roots of higher plants.
In this association,the fungal symbiont absorbs phosphorus from the soil and passes it to the plant.
Plants having such associations also 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) Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments,many of which can fix atmospheric nitrogen. In paddy fields,cyanobacteria such as $Anabaena$ and $Nostoc$ serve as an important biofertilizer. They not only add nitrogen to the soil but also add organic matter,which increases the fertility and productivity of the paddy crop by up to $50\%$. Therefore,the correct option is $A$.

(B) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$Frankia$ is a symbiotic nitrogen-fixing bacterium that forms root nodules in non-leguminous plants like $Alnus$.
$Nostoc$ is a cyanobacterium capable of fixing atmospheric nitrogen,commonly used in paddy fields to increase soil fertility.
Therefore,the pair $Frankia$ and $Nostoc$ acts as a biofertilizer.

(C) $Azolla$ is a small aquatic fern that maintains a symbiotic relationship with the nitrogen-fixing cyanobacterium $Anabaena$ $azollae$.
This cyanobacterium resides in the leaf cavities of $Azolla$.
It fixes atmospheric nitrogen into ammonia,which is then utilized by the rice plants as a natural biofertilizer.
Consequently,the presence of $Azolla$ in rice fields significantly enhances the nitrogen content of the soil,leading to increased rice production.

(B) Blue-green algae (cyanobacteria) are autotrophic microbes that are widely distributed in aquatic and terrestrial environments,many of which can fix atmospheric nitrogen,such as $Anabaena$,$Nostoc$,and $Oscillatoria$.
In paddy fields,blue-green algae serve as an important biofertilizer.
$Anabaena$ is a genus of filamentous cyanobacteria that exists as plankton and is known for its nitrogen-fixing capabilities.
$Bacillus$ is a bacterium,$Rhizobium$ is a symbiotic nitrogen-fixing bacterium found in root nodules of legumes,and $Azotobacter$ is a free-living nitrogen-fixing bacterium.

(A) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$Azolla$ is a water fern that has a symbiotic association with the nitrogen-fixing cyanobacterium $Anabaena$ $azollae$.
$BGA$ (Blue-Green Algae) like $Nostoc$ and $Anabaena$ are also well-known biofertilizers that fix atmospheric nitrogen.
Therefore,the pair $Azolla$ and $BGA$ represents biofertilizers.

(D) Statement $D$ is incorrect. The use of chemical pesticides is generally non-specific and often harmful to non-target organisms,beneficial insects,and the environment. They are not 'specific to nature' as they often cause ecological imbalances and bioaccumulation. Statements $A$,$B$,and $C$ are correct as bio-fertilizers improve soil health,chemical fertilizers cause pollution,and they are indeed costly.

(D) $BGA$ (Blue-Green Algae),such as $Anabaena$ and $Nostoc$,are prokaryotic organisms that have the ability to fix atmospheric nitrogen.
In paddy ($Oryza$ $sativa$) fields,$BGA$ serves as an important biofertilizer.
It adds organic matter to the soil and increases the fertility of the paddy fields by fixing nitrogen,which is essential for the growth of rice plants.

(C) Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria,fungi,and cyanobacteria. These microorganisms increase the availability of nutrients like nitrogen and phosphorus to the plants. According to agricultural studies and $NCERT$ data,the application of biofertilizers typically results in an increase in crop productivity by approximately $10-20\%$ compared to fields where they are not used.

(C) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$Anabaena$ is a genus of filamentous cyanobacteria that exists as plankton.
It is known for its nitrogen-fixing abilities and is widely used as a biofertilizer,especially in paddy fields,as it forms symbiotic associations with the water fern $Azolla$.

(D) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$1$. $Azolla-Anabaena$ symbiosis involves the cyanobacterium $Anabaena$ living in the leaves of the fern $Azolla$,fixing atmospheric nitrogen.
$2$. $Mycorrhiza$ is a symbiotic association between fungi and roots of higher plants,which helps in phosphorus absorption.
$3$. $Legume-Rhizobium$ symbiosis involves the bacteria $Rhizobium$ forming nodules in the roots of leguminous plants to fix nitrogen.
Since all these are examples of biofertilizers,the correct option is $D$.

(A) Organic fertilizers (biofertilizers) are organisms that enrich the nutrient quality of the soil,such as bacteria,fungi,and cyanobacteria. They are eco-friendly and do not cause pollution.
Chemical fertilizers,on the other hand,are synthetic substances that often lead to soil degradation,water pollution,and the destruction of beneficial soil microorganisms.
Since organic fertilizers provide a sustainable and pollution-free alternative to the harmful effects of chemical fertilizers,both statements are true,and $R$ correctly explains why $S$ is valid.

(C) Mycorrhiza is a symbiotic association between fungi and the roots of higher plants.
$1$. The fungal partner in mycorrhiza is typically from the genus $Glomus$.
$2$. The fungal hyphae absorb phosphorus from the soil and pass it to the plant.
$3$. In return,the plant provides the fungi with carbohydrates.
$4$. Therefore,the correct combination is $(i)$ (Fungi of the genus $Glomus$) and $(v)$ (Roots of higher plants).

(A) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$Azotobacter$ is a free-living nitrogen-fixing bacterium.
$Nostoc$ is a cyanobacterium that fixes atmospheric nitrogen.
$Mycorrhiza$ is a symbiotic association between a fungus and the roots of higher plants that helps in phosphorus absorption.
$Pseudomonas$ is primarily known as a soil bacterium that can be pathogenic or used in bioremediation,but it is not typically classified as a standard biofertilizer in the same category as the others,which are widely recognized for nitrogen fixation or nutrient uptake enhancement.

(A) Blue-green algae (Cyanobacteria) such as $Anabaena$,$Nostoc$,and $Oscillatoria$ are autotrophic microbes that are widely used in paddy fields as biofertilizers.
They possess specialized cells called heterocysts which are capable of fixing atmospheric nitrogen into organic forms like ammonia,which the plants can easily absorb.
Therefore,they primarily increase the nitrogen content of the soil,thereby enhancing soil fertility.

(D) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$1$. $Glomus$ is a fungal symbiont (mycorrhiza) that helps in phosphorus absorption.
$2$. Earthworms are known as 'farmers' friends' because they improve soil aeration and fertility through vermicomposting.
$3$. $Oscillatoria$ is a cyanobacterium that fixes atmospheric nitrogen.
$4$. Snails are mollusks that do not contribute to soil fertility as biofertilizers; in fact,they are often considered pests in agricultural fields.
Therefore,the correct option is $D$.

(C) The fungi of the genus $Glomus$ form a symbiotic association with plant roots known as $Mycorrhiza$.
These fungi help the plants in the absorption of phosphorus from the soil.
Additionally,they provide resistance to root-borne pathogens and increase tolerance to salinity and drought.
Therefore,both $A$ and $B$ are correct,making $C$ the right answer.

(D) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$1$. $Anabaena$ and $Azolla$ are classic examples of biofertilizers where $Anabaena$ (a cyanobacterium) lives in the leaf cavities of the fern $Azolla$ and fixes atmospheric nitrogen.
$2$. Cow dung and agricultural waste are organic materials that decompose to provide nutrients to the soil,acting as organic fertilizers.
$3$. The sludge left in a biogas plant is rich in organic matter and nutrients,which is also used as a fertilizer.
Therefore,all the options listed contribute to soil fertility and are considered biofertilizers or organic fertilizers.

(B) Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria,fungi,and cyanobacteria.
$1$. Nitrogen-fixing bacteria (e.g.,$Rhizobium$,$Azospirillum$,$Azotobacter$) and cyanobacteria (e.g.,$Anabaena$,$Nostoc$) fix atmospheric nitrogen into the soil,thereby reducing the need for nitrogenous chemical fertilizers.
$2$. Mycorrhizal fungi (e.g.,$Glomus$) absorb phosphorus from the soil and pass it to the plant,which helps in reducing the dependency on phosphatic chemical fertilizers.
Therefore,biofertilizers primarily help in reducing the consumption of nitrogen and phosphorus-based chemical fertilizers.

(B) Mycorrhiza is a symbiotic association between a fungus and the roots of higher plants.
Endomycorrhiza,specifically Arbuscular Mycorrhiza $(AM)$,is a type of mycorrhiza where the fungal hyphae penetrate the cortical cells of the roots.
$Glomus$ is a well-known genus of fungi that forms endomycorrhizal associations with plant roots,helping in the absorption of phosphorus from the soil.
$Nostoc$ is a cyanobacterium,$Agaricus$ is a mushroom (basidiomycete),and $Azolla$ is a water fern that forms a symbiotic relationship with $Anabaena$.

(D) In paddy fields, $Anabaena$ and $Nostoc$, which are types of $Cyanobacteria$ (also known as $Blue-green \text{ } algae$), are used as biofertilizers.
These organisms have the ability to fix atmospheric nitrogen, which enhances the fertility of the soil and promotes the growth of rice plants.
While both $Cyanobacteria$ and $Blue-green \text{ } algae$ refer to the same group, in the context of multiple-choice questions where both are present, $Blue-green \text{ } algae$ is the most commonly cited answer in textbooks for paddy field applications.

(C) $Cyanobacteria$ (blue-green algae) are autotrophic microbes that can fix atmospheric nitrogen. In paddy fields,they are widely used as biofertilizers because the flooded conditions of paddy cultivation provide an ideal environment for their growth and nitrogen fixation. They enrich the soil with nitrogen and add organic matter,which significantly increases the yield of the paddy crop.

(D) Cyanobacteria,such as Anabaena and Nostoc,are autotrophic microbes that are widely distributed in aquatic and terrestrial environments. Many of these,such as Anabaena,have specialized cells called heterocysts that fix atmospheric nitrogen. In paddy fields,cyanobacteria serve as an important biofertilizer by increasing the nitrogen content of the soil,which promotes the growth of rice plants.

(C) The correct matches are as follows:
$(a)$ $Rhizobium$ is a symbiotic nitrogen-fixing bacterium found in the root nodules of leguminous plants. Thus, $(a-iii)$.
$(b)$ $Azospirillum$ is a free-living nitrogen-fixing bacterium that lives in the soil. Thus, $(b-iv)$.
$(c)$ $Glomus$ is a genus of fungi that forms symbiotic associations with plant roots, known as $Mycorrhiza$. Thus, $(c-i)$.
$(d)$ $Cyanobacteria$ (like $Anabaena$ and $Nostoc$) are used as biofertilizers, especially in paddy fields to increase soil fertility. Thus, $(d-ii)$.
Therefore, the correct sequence is $(a-iii), (b-iv), (c-i), (d-ii)$.

(C) The correct answer is $C$.
$1$. Mycorrhiza is a symbiotic association between fungi (e.g.,$Glomus$) and roots of higher plants.
$2$. $Rhizobium$ is a well-known symbiotic nitrogen-fixing bacterium found in the root nodules of leguminous plants.
$3$. $Azotobacter$ is a free-living nitrogen-fixing bacterium.
$4$. $Azospirillum$ is also a nitrogen-fixing bacterium,but it is not a blue-green alga (Cyanobacteria). Blue-green algae (e.g.,$Anabaena$,$Nostoc$) are photosynthetic prokaryotes,whereas $Azospirillum$ is a bacterium. Therefore,the pair $C$ is incorrect.

(B) $Azotobacter$ is a well-known free-living nitrogen-fixing bacterium found in the soil.
It fixes atmospheric nitrogen into ammonia,which is then used by plants.
$Anabaena$ can be free-living or symbiotic,but $Azotobacter$ is specifically characterized as a free-living soil bacterium in the context of biofertilizers.
$Spirillum$ is a genus of bacteria,but $Azotobacter$ is the classic example of a free-living nitrogen fixer.

(A) Cyanobacteria (such as Anabaena and Nostoc) are autotrophic microbes widely distributed in aquatic and terrestrial environments,many of which can fix atmospheric nitrogen.
In paddy fields,Cyanobacteria serve as an important biofertilizer by fixing atmospheric nitrogen and adding organic matter to the soil,which increases the fertility of the field.
Rhizobium is associated with root nodules of leguminous plants.
Azotobacter is a free-living nitrogen-fixing bacterium found in soil.
$E$. coli is a bacterium found in the human intestine and is not used as a biofertilizer.

(C) Blue-green algae (Cyanobacteria) are known as biofertilizers. They are capable of fixing atmospheric nitrogen into the soil. By adding organic matter and nitrogenous compounds to the soil,they enhance the soil fertility. Therefore,they primarily increase the organic content of the soil.

(C) Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers include bacteria,cyanobacteria,and fungi.
$1$. Bacteria: Examples include $Rhizobium$ (symbiotic) and $Azospirillum$ (free-living).
$2$. Cyanobacteria: Examples include $Anabaena$,$Nostoc$,and $Oscillatoria$,which fix atmospheric nitrogen.
$3$. Fungi: $Mycorrhiza$ is a symbiotic association between fungi (e.g.,$Glomus$) and roots of higher plants,which helps in phosphorus absorption.
Therefore,the correct answer is $C$.

(D) Organic farming relies on microorganisms and certain invertebrates to improve soil fertility and plant growth.
$A$. $Glomus$ is a genus of arbuscular mycorrhizal fungi that helps in phosphorus absorption.
$B$. Earthworms are known as 'farmers' friends' as they improve soil aeration and fertility through vermicomposting.
$C$. $Oscillatoria$ is a cyanobacterium that acts as a biofertilizer by fixing atmospheric nitrogen.
$D$. Snails are generally considered pests in agriculture as they feed on crops and do not contribute to soil fertility or nutrient cycling in the context of biofertilizers. Therefore,snails are not used in organic farming.

(C) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$Rhizobium$ is a symbiotic bacterium that forms root nodules in leguminous plants,such as soybean $(Glycine \ max)$.
It fixes atmospheric nitrogen into ammonia,which the plant can utilize for growth.
Therefore,$Rhizobium$ is the correct biofertilizer used for soybean cultivation.

(A) Many members of the genus $Glomus$ form mycorrhiza,which is a symbiotic association between a fungus and the roots of higher plants. The fungal symbiont in these associations absorbs phosphorus from the soil and passes it to the plant. Therefore,$Glomus$ is the correct answer.

(C) : $Azotobacter$,$Aspergillus$,and $Trichoderma$ are all free-living microbes that contribute to plant nutrition. $Glomus$ is a genus of arbuscular mycorrhizal fungi that forms a symbiotic association with plant roots,known as endomycorrhiza. This association significantly enhances the plant's ability to absorb nutrients,particularly phosphorus,from the soil.

(A) The correct answer is $A$.
Some fungi form symbiotic associations with plants,known as mycorrhiza.
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 as well,such as resistance to root-borne pathogens,tolerance to salinity and drought,and an overall increase in plant growth and development.

(B) : $Azolla$ plays a very important role in rice production.
$Azolla$ and its nitrogen-fixing partner,$Anabaena$,have been used as green manure to fertilise rice paddies and increase production.
With the help of $Azolla$,rice can be grown year after year,several crops a year,with little or no decline in productivity; hence no rotation of crops is necessary.

(A) : Biofertilizers are organisms that enrich the nutrient quality of the soil.
The main sources of biofertilizers are bacteria,fungi,and cyanobacteria.
$Rhizobium$ bacteria are found in the root nodules of leguminous plants through a symbiotic association. These bacteria fix atmospheric nitrogen into organic forms,which are used by the plants as nutrients.
Fungi are also known to form symbiotic associations with plants called mycorrhiza.
Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments. Many of these can fix atmospheric nitrogen,$e.g.,$ $Anabaena$,$Nostoc$,$Oscillatoria$,etc.
However,$Agrobacterium$ $tumefaciens$ is a pathogen of several dicot plants. It causes crown gall disease in plants,not acting as a biofertilizer.

(C) $Rhizobium$ is used as a biofertilizer for raising soybean crops.
$Rhizobium$ $japonicum$ forms a symbiotic association in the roots of the leguminous plant,soybean,which helps in nitrogen fixation.

(B) $Azospirillum$ is a nitrogen-fixing bacterium that forms a loose association with the roots of various plants,including paddy ($Oryza$ $sativa$).
It is commonly used as a biofertilizer in paddy fields.
Inoculation of paddy fields with $Azospirillum$ helps in increasing the crop yield and reduces the requirement for chemical nitrogen fertilizers.

(D) : Organic farming is a system of agriculture that primarily aims to maintain soil health and fertility by using organic wastes and biological materials,along with beneficial microbes (biofertilizers),to release nutrients to crops for sustainable production in an eco-friendly,pollution-free environment.
Basic components of organic farming include green manures,farmyard manure,vermicompost,crop rotation,biopesticides,and biofertilizers.
$Glomus$ acts as a mycorrhizal fungus,earthworms are used in vermicomposting,and $Oscillatoria$ is a nitrogen-fixing blue-green alga; all of these are beneficial in organic farming.
Snails are not used as a component of organic farming.

(B) : The genus $Glomus$ forms endomycorrhiza,which are symbiotic associations with plants.
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.
$Nostoc$ is a blue-green alga,$Agaricus$ is a basidiomycete,and $Rhizobium$ is a eubacterium.

(B) Blue-green algae (cyanobacteria) are autotrophic microbes widely distributed in aquatic and terrestrial environments. Many of these,such as $Anabaena$ and $Nostoc$,have the ability to fix atmospheric nitrogen. When these organisms die and decompose,they add organic matter to the soil and increase its fertility. Therefore,they are widely used as biofertilizers in paddy fields.

(D) Mycorrhiza is a symbiotic association between fungi and the roots of higher plants.
Statement $(1)$ is correct: Many members of the genus $Glomus$ form mycorrhiza.
Statement $(2)$ is incorrect: Mycorrhiza helps in the absorption of phosphorus from the soil,but it is not responsible for the absorption of all minerals.
Statement $(3)$ is correct: These associations provide resistance to root-borne pathogens,increase tolerance to salinity and drought,and enhance overall plant growth.
Statement $(4)$ is incorrect: Mycorrhiza is an association between fungi and plants,not algae and plants (which is lichen).
Therefore,statements $(1)$ and $(3)$ are correct.