Find the best tutors and institutes for Class 12 Tuition
Q15:
How do biofertilisers enrich the fertility of the soil?
Solution :
Theoretical Foundation: The Concept of Biofertilizers
Biofertilizers are defined as preparations containing living cells or latent cells of efficient strains of microorganisms (bacteria, fungi, or cyanobacteria) that help in crop nutrition by increasing the availability of essential nutrients to plants through biological processes. Unlike chemical fertilizers, which provide direct mineral salts, biofertilizers promote the enrichment of soil fertility through the enhancement of the soil's natural nutrient-cycling capacity [Per the principle of Biological Nitrogen Fixation and Solubilization].
Step 1: Biological Nitrogen Fixation (BNF)
The primary mechanism for soil enrichment is the conversion of atmospheric nitrogen ($N_2$) into ammonia ($NH_3$), a form readily assimilable by plants. This process is mediated by the enzyme nitrogenase found in prokaryotes.
- Symbiotic Fixation: Genera such as Rhizobium form nodules in the roots of leguminous plants, fixing atmospheric nitrogen within the root architecture.
- Free-living Fixation: Bacteria like Azotobacter and Azospirillum reside in the soil and enrich the nitrogen pool independently [By the Law of Conservation of Nitrogen Mass in Soil Ecosystems].
Step 2: Phosphate Solubilization
Phosphorus is often trapped in insoluble forms in the soil (e.g., calcium phosphate). Biofertilizers such as Bacillus megaterium and certain fungi secrete organic acids (e.g., citric acid, gluconic acid) that lower the soil pH, thereby dissolving rock phosphate and converting it into orthophosphate ions ($H_2PO_4^-$ or $HPO_4^{2-}$) available for plant uptake.
Step 3: Enhancement of Soil Organic Matter and Structure
Biofertilizers contribute to soil fertility by increasing the organic matter content via microbial biomass turnover. Mycorrhizal fungi (e.g., Glomus) extend root surface areas through hyphal networks, significantly improving the absorption of phosphorus, water, and minerals while simultaneously secreting glomalin, which acts as a soil "glue" to improve soil aggregation and porosity.
Step 4: Comparative Analysis of Nutrient Enrichment
| Mechanism | Representative Microbes | Impact on Soil |
|---|---|---|
| $N_2$ Fixation | Rhizobium, Anabaena | Increases total nitrogen pool |
| P-Solubilization | Pseudomonas, Aspergillus | Increases bioavailable P concentration |
| Hyphal Network Expansion | Glomus (Mycorrhiza) | Improves soil structure and mineral transport |
Visual Representation of Microbial Nutrient Cycling
Synthesis of Results
Biofertilizers enrich the soil by creating a self-sustaining nutrient reservoir. By fixing atmospheric nitrogen, solubilizing locked minerals, and promoting physical aggregation via fungal mycelia, these microorganisms restore soil health without the degradation associated with synthetic inputs. This process ensures the long-term sustainability of the soil's chemical and biological profile.
Final Solution: Biofertilisers enrich soil fertility by biologically fixing atmospheric nitrogen, solubilizing inorganic phosphorus, and enhancing soil structure through microbial secretions, thereby creating a sustainable, nutrient-rich environment for plant development.
More Questions from Class 12 Biology Microbes in Human Welfare EXERCISES
- Q1: Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes with the help of a microscope, which sample would you carry and why?
- Q1: Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes with the help of a microscope, which sample would you carry and why?
- Q2: Give examples to prove that microbes release gases during metabolism.
- Q2: Give examples to prove that microbes release gases during metabolism.
- Q3: In which food would you find lactic acid bacteria? Mention some of their useful applications.
- Q3: In which food would you find lactic acid bacteria? Mention some of their useful applications.
- Q4: Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
- Q4: Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
- Q5: In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
- Q5: In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
- Q6: Name any two species of fungus, which are used in the production of the antibiotics.
- Q6: Name any two species of fungus, which are used in the production of the antibiotics.
- Q7: What is sewage? In which way can sewage be harmful to us?
- Q7: What is sewage? In which way can sewage be harmful to us?
- Q8: What is the key difference between primary and secondary sewage treatment?
- Q8: What is the key difference between primary and secondary sewage treatment?
- Q9: Do you think microbes can also be used as source of energy? If yes, how?
- Q9: Do you think microbes can also be used as source of energy? If yes, how?
- Q10: Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
- Q10: Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
- Q11: Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled \(A\), \(B\) and \(C\); but the laboratory attendant did not note which was which. The BOD values of the three samples \(A\), \(B\) and \(C\) were recorded as 20mg/L, 8mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?
- Q11: Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled (A), (B) and (C); but the laboratory attendant did not note which was which. The BOD values of the three samples (A), (B) and (C) were recorded as (20mg/L), (8mg/L) and (400mg/L), respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?
- Q12: Find out the name of the microbes from which Cyclosporin \(A\) (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.
- Q12: Find out the name of the microbes from which Cyclosporin (A) (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.
- Q13(a): Find out the role of microbes in the following and discuss it with your teacher. (a) Single cell protein (SCP)
- Q13(a): Find out the role of microbes in the following and discuss it with your teacher. (a) Single cell protein (SCP)
- Q13(b): Find out the role of microbes in the following and discuss it with your teacher. (b) Soil
- Q13(b): Find out the role of microbes in the following and discuss it with your teacher. (b) Soil
- Q14: Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd
- Q14: Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd
- Q15: How do biofertilisers enrich the fertility of the soil?
CBSE Solutions for Class 12 Biology Microbes in Human Welfare
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
Top Tutors who teach Microbes in Human Welfare
Top Tutor
Gadarpur, Gadarpur
5 yrs of
Exp
6 students
110 hrs of classes completed
500
per hour
Online Classes
I am a teacher with 7 years of experience in teaching Accountancy at school (ISC & CBSE). I have completed my graduation (Bcom) from Kurukshetra University and Post Graduation (Mcom) from IGNOU with a diploma in International Business Operations.
Explains everything as many times as you ask for. solves question with you properly and also adjust with timing.
Top Tutor
Bhamian Khurd, Ludhiana
20 yrs of
Exp
2 students
12076 hrs of classes completed
300
per hour
Online Classes
Tutor's home
I am the author of seven books and a proud recipient of the Best Teacher Award from a reputed CBSE school. With over eight years of teaching experience at the school level and fifteen years of expertise in teaching Communication Skills and English Literature at a prestigious university, I bring a strong academic foundation and practical understanding of student development. My diverse teaching background has enabled me to mentor learners with varying abilities, helping them grow intellectually, linguistically, and personally. With this rich experience, I strive to ensure the all-around development of every student, fostering confidence, clarity of thought, and a lasting appreciation for the English language.
Top Tutor
Sector 13, Dwarka, Delhi
10 yrs of
Exp
1 student
165 hrs of classes completed
500
per hour
Online Classes
Tutor's home
I am an entrepreneur, giving online classes for past couple of years. I am certified in advanced Excel and completed my MBA in 2012. I always think of learning is the best done by observing, listening and practicing what was learnt.
Top Tutor
Nigdi, Pune
6 yrs of
Exp
1 hrs of classes completed
500
per hour
Online Classes
Student's Home
Tutor's home
I have excellent teaching experience of 7 years with best results with my previous student's from CBSE , STATE and ICSE BOARD'S . Preferably i focus on students personal interest, level of understanding and study methodology. I am here to give best of me to seek best out from my students. I have given seminar on 'Students changing Virtue towards study , Need if time??' . Passionate to guide students towards there destiny
Top Tutor
Ashok Nagar, Delhi
20 yrs of
Exp
7 students
105 hrs of classes completed
750
per hour
Online Classes
Student's Home
I am teacher with over experience of 20 years. Provides complete notes and assignment. And make subject more understanding and easy.
I’ve had a great experience learning under my Accounts tuition teacher. Their way of explaining concepts is clear, practical, and easy to understand, even for tough topics like journal entries, ledgers, and financial statements. They are patient, punctual, and always open to doubts—no matter how many times I ask. Thanks to their guidance, I’ve not only improved my grades but also developed a genuine interest in the subject. Their real-world examples make learning more engaging and help me understand the application of concepts beyond the textbook.
