Discuss the role of hybridisation in crop improvement.
Soln:
Hybridization is a method of crossing two dissimilar varieties to get desirable characters in the off-springs. Hybridization improves the crop in the following attributes
High yield: Hybridization helps to improve crop yield
Pest resistance: Crop can obtain pest resistance by incorporating pest resistance genes. Ex: BT Cotton
Draught resistance: Plants obtain drought-resistant genes from drought-resistant varieties.
Disease resistance: Plants can be immune to certain disease against which genes are incorporated.
37. Define (i) Vermicompost (ii) Green manure (iii) Biofertilizer
Soln:
Vermicompost:
Manure is rich in organic materials. Vermicompost is prepared by using earthworms, plant and animal waste. Earthworms helps in composting organic waste to give nutrient-rich manure.
Green Manure:
Manure prepared by composting green plant is known as green. Green manure is usually made in the field Ex: Hemp is allowed to decompose to get green manure.
Bio-fertilizers:
Usage of living organisms to provide nutrient to plant and to make the soil fertile is known as biofertilizers. Ex: Blue-green algae used as bio-fertilizer in paddy fields.
38. Discuss various methods for weed control.
Soln:
Various methods of weed control are listed below
- Mechanical removal
- Preparation of seedbed
- Timely sowing of the desired crop
- Crop rotation
39. Differentiate between the following
(i) Capture fishery and Culture fishery
(ii) Mixed cropping and Inter cropping
(iii) Bee keeping and Poultry farming
Soln:
Capture fishery is traditional fishing where a fisherman catches the fishes from natural resources like sea and rives. Culture fishery is the one where the fishes are obtained reared for the commercial purpose.
Mixed cropping is the method of growing two or more crops in a single field. Intercropping is a type of mixed cropping where two or more crops are grown in a single field in a definite pattern.
Bee keeping is the method of rearing bees to obtain honey. Poultry farming is a method of raising domestic fowl for the purpose of egg and meat.
40. Give the merits and demerits of fish culture?
Soln:
Merits of Fish culture
Desired fishes can be obtained in a large amount in a small area.
Improved food quality as fishes is the cheap source of proteins.
Demerits of fish culture
Only desired varieties of fishes are reared
It is a threat to biodiversity.
41. What do you understand by composite fish culture?
Soln:
Composite fish culture is a method of rearing five to six varieties of fish species in a single pond. Species are selected in such a way that they should not compete with others for food because of change in their food habits. Hence fishes use food available in the pond. Ex: Catla’s are surface feeders. Rohu is middle zone feeder and common caps are bottom feeders.
42. Why bee keeping should be done in good pasturage?
Soln:
Bees need quality nectar to produce honey. A good pasturage consists of plenty of flowers which can be used by bees to get quality nectar. This increase the quality as well as the quantity of the bees. If bees are confined to only single variety of flowers for nectar honey quality will have similar taste, consistency. Most of the farmers make honey obtained from single nectar.
43. Write the modes by which insects affect the crop yield.
Soln:
Below are the modes by which insects decrease crop yield.
a) Cutting:
Insects cut plant parts such as leaves, fruits, flowers etc. This damages the plant, damaged leaves result in a decreased rate of photosynthesis, decreased flower decreases the production of seeds.
b) Borers:
Some pests boreholes in specific plant parts and start living inside. These pests utilize plant nutrients and food which result in the decrease in the yield.
c) Suckers
Few pests suck cell sap by using their proboscis. This result in an adverse effect on the plant which reduces the yield.
44. Discuss why pesticides are used in very accurate concentration and in very appropriate manner?
Soln:
Pesticides are used in very accurate and in a very appropriate manner because of the following reasons
Excess use of pesticides will reduce the fertility of the soil.
- Reduces the organic matter present in the soil
- Kills useful microorganisms present in the soil.
- Causes air, water and soil pollution.
45. Name two types of animal feed and write their functions.
Soln:
Roughage
Roughages are provided by husk, grass and chopped leaves. Roughages give complete nourishment to animals and roughages aid proper digestion in animals.
Concentrates
These are prepared as per the requirement of particular cattle and they are highly ricked in proteins and minerals. Varieties of concentrates are available in the market.
46. What would happen if poultry birds are larger in size and have no summer adaptation capacity? In order to get small sized poultry birds, having summer adaptability, what method will be employed?
Soln:
Temperature maintenance is vital for better egg production. Even though if the size of poultry birds is large but without temperature adaptation egg production may decrease. To obtain high adaptability and small-sized poultry. Crossbreeding of poultry birds is done. The small size also require small food and a small area to rear.
47. Suggest some preventive measures for the diseases of poultry birds.
Soln:
Preventive measures to avoid disease in poultry are
1.Cleaning: It is very important to maintain hygiene. Poultry farms should be cleaned regularly to maintain hygiene in the farm.
2. Sanitation: Sanitation should be maintained inside the farm
3.Disinfectatnts : Disinfectant should be sprayed on a regular basis.
4. Vaccination: Birds should be vaccinated to prevent disease in poultry.
48. Figure15.1 shows the two crop fields [Plots A and B] have been treated by manures and chemical fertilizers respectively, keeping other environmental factors same. Observe the graph and answer the following questions.
(i) Why does plot B show sudden increase and then gradual decrease in yield?
(ii) Why is the highest peak in plot A graph slightly delayed?
(iii) What is the reason for the different pattern of the two graphs?
Soln:
i) When we chemical fertilizers there will be a sudden increase in the yield as nutrients are released abundantly. But with time crop yield decrease because excess usage of chemical fertilizers kills the useful micro-organisms present in the soil and also reduces the organic material present in the soil.
ii) Manure release the nutrients slowly as they are rich in organic matter. But manure enriches the soil by providing nutrients and necessary environment for the growth of useful micro-organisms.
iii) Different pattern in the graph is due to the release of nutrients into the soil by two different methods. The graph shows that excessive usage of chemical fertilizers is detrimental and using manure is beneficial for a long time. Yield remains high when the quantity of the manure increases.
49. Complete the crossword puzzle (Fig.15.2)
Across
1. Oil yielding plant (9)
3. Crop grown in winter season (4)
5. Fixed by Rhizobium (8)
9. Common honey bee (4)
Downward
2. Animal feed (6)
4. A micronutrient (5)
6. Unwanted plant in crop fields (4)
7. An exotic breed of chicken(7)
8. Bottom feeders in fish pond(7)
10. A marine fish (4)
Soln:
Across:
1.Sunflower
3. Rabi
5. Nitrogen
9. Apis
Down
2. Fodder
4.Boron
6.Weed
7. Leghorn
8.Mrigals
10.Tuna
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