Tuesday, 12 July 2011

CBSE Class VIII (8th) Science | Chapter 1. CROP PRODUCTION AND MANAGEMENT | Lesson Exercises

1. Question :  Select the correct word from the following list and fill in the blanks.
float, water, crop, nutrients, preparation
Solution: 
(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 nutrients and water from the soil are essential.

2. Question :  Match items in column A with those in column B.
Column AColumn B
(i) Kharif crops (a) Food for cattle
(ii) Rabi crops (b) Urea and super phosphate
(iii) Chemical fertilisers (c) Animal excreta, cow dung urine and plant waste
(iv) Organic manure(d) Wheat, gram, pea
-(e) Paddy and maize

Solution : 

Column AColumn 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. Question :  Give two examples of each.
(a) Kharif crop
(b) Rabi crop
Answer :
(a) Kharif crop : The crops which are sown in the rainy season are called kharif crops. The rainy  season in India is generally from June to September.
Examples of kharif crop:
  1. Paddy
  2. Maize
  3. Soyabean
  4. Groundnut,
  5. Cotton.

(b) Rabi crop : The crops grown in the winter season are called rabi crops. Their time period is generally from October to March.
Examples of rabi crops:
  1. Wheat
  2. Gram
  3. Pea
  4. Mustard
  5. Linseed.

4. Question :  Write a paragraph in your own words on each of the following.
(a) Preparation of soil (b) Sowing (c) Weeding (d) Threshing

Answer :
(a) Preparation of soil  : The preparation of soil is the first step before growing a crop. One of the most important tasks in agriculture is to turn the soil and loosen it. This allows the roots to penetrate deep into the soil. The loose soil allows the roots to breathe easily even when they go deep into the soil.  The loosened soil helps in the growth of earthworms and microbes present in the soil. These organisms are friends of the farmer since they further turn and loosen the soil and add humus to it.turning and loosening of soil brings the nutrient-rich soil to the top so that plants can use these nutrients .
(b) Sowing : Sowing is the most important part of crop production. Before sowing, good quality seeds are selected. Good quality seeds are clean and healthy seeds of a good variety. Farmers prefer to use seeds which give a high yield.Nowadays the seed drill is used for sowing with the help of tractors. This tool sows the seeds uniformly at proper distances and depths. It ensures that seeds get covered by the soil after sowing. This prevents damage caused by birds. Sowing by using a seed drill saves time and labour
(c) Weeding : In a field many other undesirable plants may grow naturally along with the crop. These undesirable plants are called weeds. The removal of weeds is called weeding. Weeding is necessary since weeds compete with the crop plants for water, nutrients, space and light. Thus, they affect the growth of the crop. Some weeds interfere even in harvesting and
may be poisonous for animals and human beings.
(d) Threshing: In the harvested crop, the grain seeds need to be separated from the chaff. This process is called threshing. This is carried out with the help of a machine called ‘combine’ which is in fact a combined harvester and thresher.


5.Question :   Explain how fertilisers are different from manure.
Answer :

Differences between Fertiliser and Manure
Fertiliser Manure
A fertiliser is an inorganic salt.Manure is a natural substance obtained by the decomposition of cattle dung, human waste and plant residues.
A fertiliser is prepared in factories. Manure provides a lot of humus to the soil.
A fertiliser does not provide any humus to the soil.Manure provides a lot of humus to the soil.
Fertilisers are very rich in plant nutrients like nitrogen, phosphorus and potassium.Manure is relatively less rich in plant nutrients.

6. Question :  What is irrigation? Describe two methods of irrigation which conserve water.
Answer :
  Irrigtion : All living beings need water to live. Water is important for proper growth and development of flowers, fruits and seeds of plants. Water is absorbed by the plant roots.Along with water, minerals and fertilisers are also absorbed. Plants contain nearly 90% water. Water is essential because germination of seeds does not take place under dry conditions.The supply of water to crops at different intervals is called irrigation. The time and frequency of irrigation varies from crop to crop, soil to soil and season to season.
Two methods of Irrigation which conserve water :
(i) Sprinkler System: This system is more useful on the 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. Sprinkler is very useful for sandy soil.
(ii) Drip system : In this system, the water falls drop by drop just at the position of the roots. So it is called drip system. It is the best technique for watering fruit plants, gardens and trees. The system provides water to plants drop by drop. Water is not wasted at all. It is a boon in regions where availability of water is poor.

7. Question :  If wheat is sown in the kharif season, what would happen? Discuss.
Answer : Wheat is a  rabi crop, which is  grown in the winter season . Rabi crops are generally sown  from October to March and rquire less water, low temperature, less humidity and moderate shunshine. Where as kharif crops are sown in the rainy season generally from June to September as these require a lot of water, excess tempreture, humidity. Therefor,  If wheat is sown in the kharif season, due to entirely adverse climatic conditions it will not yield any crop.

8.Question :   Explain how soil gets affected by the continuous plantation of crops in a field.
Answer : Continuous growing of crops makes the soil poorer in certain nutrients. Therefore, lateral farming of these crops, we have to add manure to the fields to replenish the soil with nutrients.

9. Question :  What are weeds? How can we control them?
Answer :
Weeds : In a field many other undesirable plants may grow naturally along with the crop. These undesirable plants are called weeds.The removal of weeds is called weeding. Weeding is necessary since weeds compete with the crop plants for water, nutrients, space and light. Thus, they affect the growth of the crop.
To controle weeds we can do the following things :
 Tilling before sowing of crops helps in uprooting and killing of weeds, which may then dry up and get mixed with the soil. The best time for the removal of weeds is before they produce flowers and seeds. The manual removal includes physical removal of weeds by uprooting or cutting them close to the ground, from time to time using a khurpi. We can also use a seed drill for the same.
Weeds are also controlled by using certain chemicals, called weedicides. These are sprayed in the fields to kill the weeds. They do not damage the crops. The weedicides are diluted with water to the extent required and sprayed in the fields with a sprayer.

10.Question :   Arrange the following boxes in proper order to make a flow chart of sugarcane crop production.
Sending crop to sugar factory IrrigationHarvestingSowing
1234
Preparation of soilPloughing the fieldManuring-
567-

Solution :


Preparation of soilPloughing the fieldSowingManuring
1234
IrrigationgHarvestingSending crop to sugar factory -
567-



11.Question :   Complete the following word puzzle with the help of clues given below.

- - 1-I - - - 2-S - -
3-H - - - - - - - -
- - - - - - - - -
- - - - - - - - -
4-G - - - - - - - -
- - - - - - - - -
- - - - - - - - -
- - - - - - - - -
- - - - 5-C - - - -
6-W - - - - - - - -
- - - - - - - - -


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 grown on a large scale.
Across
3. A machine used for cutting the matured crop.
4. A rabi crop that is also one of the pulses.
6. A process of separating the grain from chaff.
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Chapter 1. CROP PRODUCTION AND MANAGEMENT | Lesson Exercises | CBSE Class VIII (8th) Science

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