Crop Production and Management - Exemplar Solutions 1

CBSE Class 08 Science
NCERT Exemplar Solutions
Crop Production and Management

1. Which one of the following condition is not essential to grow maize?
(a) High temperature
(b) Humidity
(c) Low temperature
(d) Rainfall
Ans. (c) Maize belongs to the group of crops belonging to subtropical origin and is highly reactive towards higher temperature. This variety of crop is susceptible to low temperatures, and it does not adjust to with such temperature due to which cultivation in temperature latitudes is limited.

2. Propagation of ginger is generally done using
(a) seed
(b) stem (rhizome)
(c) root
(d) leaf
Ans. (b) Propagation of ginger takes place through stems of ginger. It propagates below the ground and it multiplies through the rhizomes.

3. Which of the following statement is not true for organic manure?
(a) It enhances water holding capacity of soil.
(b) It has a balance of all plant nutrients.
(c) It provides humus to soil.
(d) It improves texture of soil.
Ans. (b) The basic nutrients required by plants for proper growth are nitrogen (N), phosphorus (P), and potassium(K). But phosphorus and potassium cannot be added to soil by organic approaches as organic matter in soil undergoes decomposition with the help of decomposers present in the soil and finally ends up by getting converted into carbon dioxide, nitrogen, Sulphur oxides, water and keeps on restoring the nutrients by natural processes including carbon, nitrogen and Sulphur cycles.  

4. The term used for the process of separation of grains from chaff is
(a) sieving
(b) threshing
(c) winnowing
(d) hand picking
Ans. (b) The term used for the process of separation of grains from chaff is Threshing. Winowing is used to separate grains and chaff by the farmers, manually, who have small holdings of land.

5. Read the statements given below.
(i) Seeds require moisture for germination.
(ii) Plants can absorb nutrients mostly in dissolved form.
(iii) Irrigation protects crops from both frost and hot air currents.
(iv) Irrigation improves soil texture.
Choose the combination of statements which indicate the need to irrigate crops.
(a) i and ii
(b) i, ii, iii
(c) i, ii, iii, iv
(d) i and iii
Ans. (c) Seeds require moisture for germination because they remain dormant as long as they are dry. But presence of water unstiffens the seed coat and expands the protoplasm thereby leading to the germination. Plants absorbs the water through their roots from soil. Along with water they get absorbed the nutrients dissolved in water. Irrigation improves the texture of soil and helps in maintaining the soil temperature.

6. Which of the following tools would a farmer use to remove weeds from the field?
(a) Hoe
(b) Plough
(c) Axe
(d) Cultivator
Ans. (a) Hoe is a simple wooden tool pulled by animals and is used to remove weeds from soil as well as to loosen the soil. It consists of a long wooden or iron rod with a strong, wide-ranging and bent iron plate fixed at its end that acts like a blade.

7. Which of the following is not true for fertilisers?
(a) They increase the yield.
(b) Their excessive use disturbs the balance of nutrients in soil.
(c) They are generally used in small quantity.
(d) They are environment friendly.
Ans. (d) The statement that fertilizers are environment friendly is not at all true because they are highly concentrated and has the potential to burn the plant roots and can even kill the microorganisms present in soil. It reduces the water and nutrient holding capacity of soil and increase the level of toxic chemicals in soil that can be in turn absorbed by the plants. It also eliminates the earthworms that plays a pivotal role in improving the soil quality by replenishing the soil aeration and natural fertilization. Excessive use of fertilizers leads to water pollution. Fertilizers decrease the fertility of soil,

8. Given below are statements about the harmful effects of weeds on crop plants.
(i) They interfere in harvesting.
(ii) They help crop plants to grow healthily.
(iii) They compete with crop plants for water, nutrients, space and light.
(iv) They affect plant growth.
Choose the correct combination of statements.
(a) i, iii, iv
(b) iii only
(c) iii, iv
(d) i, ii, iii, iv
Ans. (a) The unwanted plants that grows along with the crops are known as weeds. They compete with the crops for water, nutrients, light and space thereby affecting their growth. They also interfere during harvesting.

9. The process of loosening and turning of soil is called
(a) irrigation and manuring
(b) digging and winnowing
(c) tilling and ploughing
(d) harvesting and storage
Ans. (c) Nutrients are presents in soil up to a small depth. Therefore, turning and loosening of soil brings the nutrient rich soil to the top which enables the plants to acquire more nutrients from soil. This process of loosening and turning of soil is termed as tilling and ploughing.

10. The monsoon season in our country is during the months
(a) April to December
(b) June to September
(c) November to March
(d) January to May
Ans. (b) The monsoon season in India persists from June to September.

11. The system of irrigation where in water is supplied drop by drop near the roots of plants, is called
(a) pulley system
(b) drip system
(c) sprinkler system
(d) lever system
Ans. (b) The system of irrigation where in water is supplied drop by drop near the roots of plants is called drip system. As the water falls drop by drop at the position of the root therefore the name drip system. Water is not at all wasted in this technique and it stands out to be a boon in the regions with poor water availability.