The Class 8 is an important year in a student’s life and Science is one of the subjects that require dedication, hard work, and practice. It’s a subject where you can score well if you are well-versed with the concepts, remember the important formulas and solving methods, and have done an ample amount of practice. Worry not! Home Revise is here to make your Class 8 journey even easier. It’s essential for students to have the right study material and notes to prepare for their board examinations, and through Home Revise, you can cover all the fundamental topics in the subject and the complete NCERT Class 8 Science Book syllabus.
Exercise Questions
1. Select the correct word from the following list and fill in the blanks.
float, water, crop, nutrients, preparation
(a) The same kind of plants grown and cultivated on a large scale at a place is called _____________.
(b) The first step before growing crops is _____________ of the soil.
(c) Damaged seeds would _____________ on top of water.
(d) For growing a crop, sufficient sunlight and _____________ and _____________ from the soil are essential.
Soln:
(a) The same kind of plants grown and cultivated on a large scale at a place is called the crop .
(b) The first step before growing crops is the preparation of the soil.
(c) Damaged seeds would float on top of the water.
(d) For growing a crop, sufficient sunlight and water and nutrients from the soil are essential.
2. Match items in column A with those in column B.
| A | B |
| (i) Kharif crops | (a) Food for cattle |
| (ii) Rabi crops | (b) Urea and superphosphate |
| (iii) Chemical fertilisers | (c) Animal excreta, cow dung urine and plant wastes |
| (iv) Organic manure | (d) Wheat, gram, pea |
| (e) Paddy and maize |
Soln:
| (i) Kharif crops | (e) Paddy and maize |
| (ii) Rabi crops | (d) Wheat, gram, pea |
| (iii) Chemical fertilisers | (b) Urea and superphosphate |
| (iv) Organic manure | (c) Animal excreta, cow dung urine and plant wastes |
3. Give two examples of each.
(a) Kharif crop
(b) Rabi crop
Soln:
Kharif crops – Paddy and maize
Rabi crops – Wheat and pea
4. Write a paragraph in your own words on each of the following.
(a) Preparation of soil
(b) Sowing
(c) Weeding
(d) Threshing
Soln:
a) Preparation of the soil is the first step in agriculture. Preparation of the soil is done to loosen the soil, which is essential for root penetration into the soil. This allows the roots to breathe easily. Loosening of the soil allows the growth of earthworms and microorganisms, which will help to keep the soil fertile by adding humus to the soil. Loosening of soil also brings nutrient-rich soil to the top layer, which is essential for the growth of plants.
b) Sowing is an important process in crop production. First, healthy seeds are selected before sowing. After selecting healthy seeds, sowing is done by either traditional methods or by using the equipment’s seed drill.
c) Removal of unnecessary plants from the field is called weeding. Weeds compete with crop plants for nutrients and water. This will reduce the yield of the desired crops. Weeds also interfere while harvesting and get mixed with crops. Some weeds are poisonous to animals and humans. Tilling is a common method that helps remove weeds before sowing crops, and manual methods like the physical removal of plants are also used to remove weeds. Weedicides are sprayed to get rid of weeds, but this method may affect the health of farmers because of the chemicals used as weedicides.
d) Process of separating the chaff from the crop is known as threshing. Threshing is carried by a machine called ‘combine’, which is a harvester as well as a thresher. Threshing is also done by winnowing, where the blow of air is used to separate the chaff from crops.
5. Explain how fertilisers are different from manure.
Soln:
| Fertilisers | Manure |
| Fertiliser is an inorganic substance. | Manure is an organic substance. |
| Fertilisers are prepared artificially. | Manure is obtained by the decomposition of animal, plant and human waste. |
| Prepared in factories. | Prepared in fields. |
| Does not provide humus to the soil. | Provide humus to the soil. |
| Rich in plant nutrients. | Relatively less plant nutrients. |
| Long-term usage has adverse effects on soil. | Long-term usage improves soil fertility. |
6. What is irrigation? Describe two methods of irrigation which conserve water.
Soln:
The supply of water to crops at regular intervals is called irrigation. Methods of irrigation which conserve water are as follows:
a) Drip Irrigation: Here, the water goes drop by drop directly into the roots; this method is very useful as it conserves the water and also helps in avoiding weeds.
b) Sprinkler system: This method is in use mainly in uneven land where sufficient water is not available. The perpendicular pipes, having rotating nozzles on top, are joined to the main pipeline at regular intervals. When water is allowed to flow through the main pipe under pressure with the help of a pump, it escapes from the rotating nozzles. It gets sprinkled on the crop as if it is raining.
7. If wheat is sown in the Kharif season, what would happen? Discuss.
Soln:
Wheat crops may get destroyed if sown in the Kharif season because of unfavourable temperatures, pests and adaptable conditions for the plants to grow. Kharif comes during the rainy season; hence it is not a wise idea to grow wheat in the Kharif season.
8. Explain how soil gets affected by the continuous plantation of crops in a field.
Soln:
Plants require nutrients for their growth. Without optimum nutrients, plants will die. Continuous plantation of crops results in the depletion of certain nutrients like Nitrogen, Phosphorus, Potassium, etc. This results in a decrease in yield due to loss of nutrients; hence there should be a gap between crops in order to get a good yield.
9. What are weeds? How can we control them?
Soln:
In a field, many other undesirable plants may grow naturally along with the crop. These undesirable plants are called weeds. Weeds can be controlled by methods called weeding. Tilling before sowing the crops helps in uprooting and killing weeds, which may then dry up and get mixed with the soil. Weeds are also controlled by using certain chemicals called weedicides.
10. Arrange the following boxes in proper order to make a flow chart of sugarcane crop production.
Soln:
11. Complete the following word puzzle with the help of the clues given below.
Down
1. Providing water to the crops.
2. Keeping crop grains for a long time under proper conditions.
5. Certain plants of the same kind are grown on a large scale.
Across
3. A machine used for cutting the matured crop.
4. A rabi crop, which is also one of the pulses.
6. A process of separating the grain from the chaff.
Soln:
