Science STD 8 Chapter 1: Crop Production and Management - Exercises
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 crop.
- (b) The first step before growing crops is preparation of the soil.
- (c) Damaged seeds would float on top of water.
- (d) For growing a crop, sufficient sunlight and water from the soil are essential.
2. Match items in column A with those in column B.
| A | B |
|---|---|
| (i) Kharif crops | (e) Paddy and maize |
| (ii) Rabi crops | (d) Wheat, gram, pea |
| (iii) Chemical fertilisers | (b) Urea and super phosphate |
| (iv) Organic manure | (c) Animal excreta, cow dung, urine and plant waste |
3. Give two examples of each.
- (a) Kharif crop
Paddy, Maize
- (b) Rabi crop
Wheat, Gram
4. Write a paragraph in your own words on each of the following.
- (a) Preparation of soil
Preparation of soil is the first and most important step before sowing a crop. This process, also known as tilling or ploughing, involves loosening and turning the soil. This allows the roots to penetrate deep and breathe easily. It also helps in the growth of beneficial microorganisms and earthworms. Turning the soil brings the nutrient-rich layers to the top, which is essential for plant growth. This is done with a plough, hoe, or cultivator.
- (b) Sowing
Sowing is the process of placing seeds in the soil after it has been prepared. Before sowing, it is crucial to select good quality, healthy seeds to get a better yield. Seeds can be sown using traditional tools like a funnel-shaped tool or modern tools like a seed drill. The seed drill ensures that seeds are sown uniformly at the correct depth and distance, which protects them from birds and prevents overcrowding. This method saves both time and labour.
- (c) Weeding
Weeding is the process of removing unwanted plants, called weeds, that grow naturally alongside the main crop. Weeds compete with the crop for sunlight, water, space, and nutrients, which can affect the crop's growth. Weeding can be done manually by uprooting the weeds with a khurpi or by using a seed drill. Farmers also use chemical substances called weedicides to kill weeds without harming the crop. The best time for weeding is before the weeds produce flowers and seeds.
- (d) Threshing
Threshing is the process of separating the harvested grain from the chaff. This is a crucial step after harvesting a crop. It can be done by a machine called a combine, which is a harvester and thresher combined. For farmers with small landholdings, this is done by a process called winnowing, which separates the grain from the chaff using wind.
5. Explain how fertilisers are different from manure.
| Fertilisers | Manure |
|---|---|
| Fertilisers are inorganic, man-made salts. | Manure is a natural substance obtained from the decomposition of organic waste. |
| They are prepared in factories. | It can be prepared in the fields. |
| They do not provide humus to the soil. | It provides a lot of humus to the soil. |
| They are very rich in specific nutrients like nitrogen, phosphorus, and potassium. | It is relatively less rich in plant nutrients. |
6. What is irrigation? Describe two methods of irrigation which conserve water.
Irrigation is the supply of water to crops at regular intervals. The time and frequency of irrigation vary depending on the crop, soil type, and season. The two modern methods of irrigation that conserve water are:
- Sprinkler System: This system uses rotating nozzles attached to perpendicular pipes that are connected to a main pipeline. When water is pumped under pressure, it is sprinkled on the crop as if it is raining. This method is highly useful for uneven land and saves a lot of water.
- Drip System: In this system, water is delivered drop by drop directly to the roots of the plants. This is the most efficient method of irrigation as water is not wasted at all. It is a boon in regions where water is scarce and is best for watering fruit plants, gardens, and trees.
7. If wheat is sown in the kharif season, what would happen? Discuss.
Wheat is a rabi crop and is grown in the winter season. If it is sown in the kharif season (June to September), it will not grow well. The kharif season is the rainy season in India, and wheat plants are not adapted to withstand the high temperatures and excessive water. The plants would be susceptible to pests, diseases, and damage from heavy rain, leading to a poor yield or crop failure. Therefore, it is important for crops to be grown in their appropriate season.
8. Explain how soil gets affected by the continuous plantation of crops in a field.
The continuous plantation of crops in a field makes the soil poor in nutrients. Plants absorb essential minerals and nutrients from the soil for their growth. When the same crop is grown repeatedly, the soil's nutrient content is depleted. This lack of nutrients makes the soil less fertile, leading to weak plants and a lower yield. Farmers must add manure and fertilisers or practice crop rotation to replenish the soil's nutrients.
9. What are weeds? How can we control them?
Weeds are undesirable plants that grow naturally with a crop. They compete with the crop plants for water, nutrients, light, and space, affecting the growth of the main crop. Some weeds can also be poisonous to animals and humans. Weeds can be controlled in the following ways:
- **Tilling:** Ploughing the soil before sowing helps in uprooting and killing the weeds.
- **Manual removal:** Weeds can be physically removed by uprooting them or cutting them close to the ground using a tool like a khurpi.
- **Using weedicides:** Chemicals like 2,4-D can be sprayed in the fields to kill weeds without damaging the crop.
10. Arrange the following boxes in proper order to make a flow chart of sugarcane crop production.
The correct order for a flowchart of sugarcane crop production is:
- Preparation of soil
- Ploughing the field
- Sowing
- Manuring
- Irrigation
- Harvesting
- Sending crop to sugar factory
11. Complete the following word puzzle with the help of clues given below.
Down
- Providing water to the crops. IRRIGATION
- Keeping crop grains for a long time under proper conditions. STORAGE
- Certain plants of the same kind grown on a large scale. CROP
Across
- A machine used for cutting the matured crop. HARVESTER
- A rabi crop that is also one of the pulses. GRAM
- A process of separating the grain from chaff. WINNOWING
Suggested Activities and Projects
1. Sow some seeds in the soil and arrange to water them by drip irrigation. Observe daily. (i) Do you think it can save water? (ii) Note the changes in the seed.
Outline: This is a hands-on activity to demonstrate the efficiency of the drip irrigation system. By watering seeds with this method, you would observe that it conserves water because water is delivered directly to the roots, with no waste due to evaporation. You would also note the consistent and healthy growth of the seeds, highlighting the benefits of precise watering.
2. Collect different types of seeds and put them in small bags. Label them.
Outline: This activity promotes an understanding of seed diversity and agricultural practices. By collecting and labelling different types of seeds (e.g., from various cereals, fruits, and vegetables), you would learn to identify different crops by their seeds. This activity also emphasizes the importance of proper storage of seeds.
3. Collect pictures of some other agricultural machines and paste them in a file. Write their names and uses.
Outline: This project is about researching modern farming technology. You would collect pictures of machines like tractors, ploughs, cultivators, seed drills, and combine harvesters. You would then write down their names and explain how each machine is used in different agricultural practices, from tilling the soil to harvesting crops. This activity highlights how technology has modernised agriculture, saving time and labour.
4. Project Work. Visit a farm, nursery or a garden nearby. Gather information about (i) importance of seed selection. (ii) method of irrigation. (iii) effect of extreme cold and extreme hot weather on the plants. (iv) effect of continuous rain on the plants. (v) fertilisers/manure used.
Outline: This is an excellent field trip project to gain firsthand knowledge of farming. You would interview a farmer or gardener to understand the importance of selecting high-quality seeds for a good yield. You would also learn about their irrigation methods (e.g., traditional vs. modern), how they protect their crops from adverse weather, and the different types of fertilisers or manure they use to maintain soil fertility.