B. Sun hemp (Crotalaria juncea / Sunn hemp) and Guar (cluster beans)
15.
What are BIOFERTILIZERS as mentioned in NCERT Class 9?
A.
Biofertilizers are chemical fertilisers derived from biological sources
B.
Biofertilizers are compost prepared using biological waste materials only
C.
Biofertilizers are synthetic fertilisers modelled on the structure of animal hormones
D.
Biofertilizers are living organisms (bacteria, fungi, cyanobacteria/blue-green algae) that help plants absorb nutrients from the soil by fixing atmospheric nitrogen or making phosphorus available
D. Biofertilizers are living organisms (bacteria, fungi, cyanobacteria/blue-green algae) that help plants absorb nutrients from the soil by fixing atmospheric nitrogen or making phosphorus available
16.
Blue-green algae (Cyanobacteria) are used as biofertilisers particularly in the cultivation of:
A.
Sugarcane plantations in tropical areas
B.
Paddy (rice) fields — they fix atmospheric nitrogen and improve soil fertility
B. Manure: improves soil texture, adds humus, environment-friendly, improves water-holding capacity, reduces soil erosion, slow-release of nutrients
18.
What are the DISADVANTAGES/LIMITATIONS of manure compared to chemical fertilisers?
A.
Manure: bulky and difficult to transport, less concentrated in specific nutrients, slow-acting (takes time for nutrients to become available), requires large quantities per hectare
B.
Manure reduces the water-holding capacity of soil
C.
Manure is toxic to soil microorganisms
D.
Manure causes water pollution more than chemical fertilisers
A. Manure: bulky and difficult to transport, less concentrated in specific nutrients, slow-acting (takes time for nutrients to become available), requires large quantities per hectare
