1. Which of the following is/are used as biofertilizers?
1. Azolla
2. Blue-green algae
3. Alfalfa
Choose the correct answer by the given codes :
(a) only 2
(b) 1 and 2
(c) 1 and 3
(d) 1, 2 and 3
[I.A.S. (Pre) 1994, U.P.P.C.S. (Pre) 2002 , U.P.P.C.S. (Pre) 2001]
Ans. (b) 1 and 2
- Biofertilizers are special microorganisms like bacteria and algae that help plants absorb more nutrients from the soil.
- They make the nutrients in the soil easier for plants to take in.
- There are different types of biofertilizers that help with different things, like nitrogen-fixing, phosphorus-solubilizing, and micronutrients.
- Some examples are Azotobacter, Rhizobium, Pseudomonas, and Cyanobacteria.
- Alfalfa is a plant that is also used as a biofertilizer.
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2. Which of the following is used as a Biofertilizer?
(a) Rhizobium
(b) Blue-green algae
(c) Azolla
(d) All of these
[Chhattisgarh P.C.S. (Pre) 2019,Uttarakhand P.C.S. (Mains) 2002]
Ans. (d) All of these
- Rhizobium, Blue-green algae, and Azolla are all types of biofertilizers that help the soil to contain nitrogen.
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3. Which of the following is not a nitrogen-fixing organism?
(a) Nostoc
(b) Anabaena
(c) Azotobacter
(d) Mycorrhiza
[U.P. P.C.S. (Mains) 2017]
Ans. (d) Mycorrhiza
- Nostoc, Anabaena, and Azotobacter are bacteria that help to put nitrogen in the soil.
- Mycorrhiza is a partnership between fungi and plants.
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4. Which of the following is a source of bio-fertilizer?
(a) Yeast
(b) Chlorella
(c) Azolla
(d) Mold
[U.P.P.C.S. (Mains) 2009, U.P.P.C.S. (Spl) (Mains) 2008, Uttarakhand P.C.S. (Mains) 2002]
Ans. (c) Azolla
- Azolla has the ability to take nitrogen from the air and turn it into something plants can use.
- This makes it a popular fertilizer in Southeast Asia.
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5. The biofertilizer used as a supplementary food for the cattle, especially for milking bovines is :
(a) Azospirillum
(b) Azolla
(c) Azotobacter
(d) Rhizobium
[R.A.S./R.T.S. (Pre) 2016]
Ans. (b) Azolla
- Animal farming in India is becoming more profitable due to the demand for milk and meat.
- However, there is not enough fodder for livestock.
- An alternative is Azolla, a plant with a high protein content.
- This special plant has an amazing relationship with algae, which helps it to grow and develop.
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6. Nitrogen-fixing bacteria make combinations with cells of the roots of
(a) Pulses
(b) Rice
(c) Wheat
(d) Sugarcane
[U.P.P.C.S. (Pre) 2019]
Ans. (a) Pulses
- Usually, bacteria that can capture nitrogen from the air are found in the roots of legumes (plants that produce beans, peas, etc.) in a special structure known as root nodules.
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7. Which of these is not correctly matched
(a) Blue-green algae – Bio-fertilizer
(b) Chrysopa – Maho-control
(c) Bio 902 – Variety of mustard
(d) Azotobacter – Bioinsecticide
[U.P.Lower Sub. (Spl.) (Pre) 2003 U.P.Lower Sub. (Spl.) (Pre) 2002]
Ans. (d) Azotobacter – Bioinsecticide
- Azotobacter is a type of bacteria that helps plants by taking nitrogen from the air around the roots and using it.
- The answer “d” is incorrect, but the other three answers are correct.
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8. Which of the following is associated with biological nitrogen fixation?
(a) Red algae
(b) Brown Algae
(c) Green algae
(d) Blue-green algae
[U.P.P.C.S. (Pre) 2019]
Ans. (d) Blue-green algae
- Blue-green algae is another name for Cyanobacteria.
- It helps with making nitrogen available for living things.
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9. Blue-green algae are chiefly used as biofertilizers in the crop of
(a) Wheat
(b) Gram
(c) Paddy
(d) Mustard
[U.P.P.C.S. (Pre) 2006]
Ans. (c) Paddy
- Cyanobacteria, also known as blue-green algae, is a type of fertilizer that helps to take nitrogen from the air and put it into the soil.
- This type of fertilizer is especially useful for growing crops such as rice.
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10. Blue-green algae is used to supply nitrogen to –
(a) Bajra
(b) Maize
(c) Paddy
(d) Wheat
[U.P.P.C.S. (Mains) 2010]
Ans. (c) Paddy
- Cyanobacteria, also known as blue-green algae, is a type of biofertilizer that helps to take nitrogen from the air and make it usable for plants.
- It is mostly used on paddy crops.
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11. Which one of the following is not correctly matched?
| Nitrogen-fixing agent |
Crop |
| Blue-green algae |
Paddy |
| Rhizobium Leguminosarum |
Pea |
| Azotobacter |
Wheat |
| Azolla |
Maize |
[U.P.P.C.S. (Pre) 2017]
Ans. (d) Azolla – Maize
- Option (d) is correct answer.
- Azolla, Anabaena, Nostok, and blue-green algae promote nitrogen fixation in paddy harvesting and work as organic fertilizers.
- Rhizobium leguminosarum is used in peas and Azotobacter in wheat to promote nitrogen fixation.
- Azolla is not used for nitrogen fixation in maize.
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12. Azolla gives a good biofertilizer when mixed with –
(a) Blue-green algae
(b) Bone meal
(c) Cow dung
(d) Urea
[Uttarakhand P.C.S. (Pre) 2007]
Ans. (a) Blue-green algae
- Azolla is a type of water fern that can be mixed with blue-green algae or cyanobacteria to create a good fertilizer for rice fields.
- It can also help change the physical, chemical, and biological properties of the soil and water near the rice fields.
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13. Azolla is often used as a biofertilizer because it is associated with –
(a) Blue-green algae
(b) Red algae
(c) Fungus
(d) Moss
[U.P.P.C.S. (Mains) 2011]
Ans. (a) Blue-green algae
- Azolla is a type of water fern.
- When mixed with blue-green algae or cyanobacteria, it can act as a powerful fertilizer for rice fields.
- It can also make changes to the physical, chemical, and biological properties of the soil and the area around the rice fields.
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14. Azolla is –
(a) Aquatic Fern
(b) Aquatic algae
(c) Aquatic bacteria
(d) None of these
[U.P. U.D.A./L.D.A. (Spl.) (Mains) 2010]
Ans. (a) Aquatic Fern
- Azolla is a type of water fern.
- When mixed with blue-green algae or cyanobacteria, it makes a great fertilizer and adds nitrogen to rice fields.
- It also helps change the physical, chemical, and biological elements of the soil and water in rice fields.
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15. Aquatic Fern, which is used as a biofertilizer, is
(a) Salvinia
(b) Azolla
(c) Marsilia
(d) Pteridium
[U.P.R.O./A.R.O. (Mains) 2014]
Ans. (b) Azolla
- Azolla is a type of fern that grows in water.
- When mixed with BGA or cyanobacteria, it makes a great fertilizer and helps rice fields get the nitrogen they need.
- Azolla also changes the physical, chemical, and biological features of the soil and water in rice fields.
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16. Which of the following microorganisms are used as biofertilizers?
(a) Virus
(b) Fungi
(c) Protozoa
(d) Cyanobacteria
[U.P. R.O./A.R.O. (Mains) 2016 U.P. P.C.S. (Mains) 2012]
Ans. (d) Cyanobacteria
- Azolla is a type of fern that grows in water and it can be used to give a natural fertilizer when combined with blue-green algae or cyanobacteria.
- It supplies nitrogen to rice fields and can also change the physical, chemical, and biological properties of the soil and water around rice fields.
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17. Which of the following is phosphatic biofertilizer?
(a) Rhizobium
(b) Blue-green algae
(c) Azolla
(d) Vascular Arbuscular Mycorrhiza
[U.P. B.E.O. (Pre) 2019]
Ans. (d) Vascular Arbuscular Mycorrhiza
- Rhizobium, Blue-green algae (Cyanobacteria), and Azolla can fix nitrogen in the soil.
- Vascular Arbuscular Mycorrhiza (VAM) helps plants to absorb phosphorus better.
- VAM fungi help plants by getting more water, minerals, and especially phosphorus, which is hard to get.
- It also makes plants more resistant to diseases and better able to handle tough conditions like drought.
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18. What is the use of biochar in farming?
1. Biochar can be used as a part of the growing medium in vertical farming.
2. When biochar is a part of the growing medium, it promotes the growth of nitrogen-fixing microorganisms.
3. When biochar is a part of the growing medium, it enables the growing medium to retain water for a longer time.
Which of the statements given above is/are correct?
(a) 1 and 2 only
(b) 2 only
(c) 1 and 3 only
(d) 1, 2 and 3
[I.A.S. (Pre) 2020]
Ans. (d) 1, 2 and 3
- Biochar is a type of charcoal made by heating organic materials like crop waste, grass, woodchips, and manure in a high-temperature, low-oxygen process.
- It can be used in vertical farming and added to soil to increase its carbon content and reduce greenhouse gas emissions.
- Some biochars can also help improve soil fertility, water-holding capacity, and crop productivity.
- Research suggests that grasses and crops are the best balance between benefits and carbon stability.
- Studies also show that increasing the application rate of biochar can have a positive effect on biological nitrogen fixation and soil microbial biomass.
- Biochar is good at retaining water and nutrients and providing a suitable habitat for beneficial soil microorganisms.
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19. The capability of nitrogen use efficiency can be increased in crop production by
(a) Use of split application
(b) Use of nitrogen inhibitors
(c) Using the slow release of nitrogen fertilizer
(d) All of the above.
[U.P.P.C.S. (Pre) 2009]
Ans. (d) All of the above.
- All of the given methods can help to make the use of nitrogen more efficient:
- using fertilizer often and in smaller amounts
- using nitrogen inhibitors
- using slow-release nitrogen fertilizer
- Certain bacteria in crops are responsible for stabilizing nitrogen.
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20. Which bacteria is responsible for nitrogen fixation in soyabean?
(a) Rhizobium leguminosarum
(b) Rhizobium japonicum
(c) Rhizobium fagioli
(d) Rhizobium traitolai
[U.P.P.C.S. (Pre) 2006]
Ans. (b) Rhizobium japonicum
- The Rhizobium japonicum bacteria helps soybeans to fix nitrogen.
- When soybeans are given the Rhizobium japonicum bacteria with the hydrogenase system, the soybeans are able to fix more nitrogen.
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21. Leg-haemoglobin is found in –
(a) Human blood
(b) Rabbit blood
(c) Legume root nodules
(d) Chicken blood
[U.P.P.C.S. (Mains) 2005]
Ans. (c) Legume root nodules
- Leg-haemoglobin is located in the root nodules of certain plants like alfalfa and soybean.
- It is very important to provide enough oxygen to the root nodule bacteria so they can fix nitrogen.
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