NCERT Solutions Class 8 Science Crop production and management

NCERT Solutions for Class 8 Science for chapter 1 Crop production and management

Exercises

Question- 1. Select the following 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 crop is ______of the soil.
c) Damaged seed would ______ on top of water.
d) For growing a crop, sufficient sunlight and _____ and____ from the soil are essential.

Answer:

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 crop is preparation of the soil.
c) Damaged seed would float on top of water.
d) For growing a crop, sufficient sunlight and water and nutrients from the soil are essential.

 

Question- 2 Match items in column A with those in column B.

Column A

Column B

Kharif crops

Food for cattle

Rabi crops

Urea and super phosphate

Chemical fertlilisers

Animal excreta, cow dung, urine and plant waste

Organic manure

Wheat, gram, pea

 

Paddy and maize

Answer:

Column A

Column B

Kharif crops

Paddy and maize

Rabi crops

Wheat, gram, pea

Chemical fertlilisers

Urea and super phosphate

Organic manure

Animal excreta, cow dung, urine and plant waste


Question- 3 Give two examples of each:

a) Kahrif crop b) Rabi crop

Answer:

a) Two examples of Kharif crop are paddy and maize. b)Two examples of rabi crops are wheat and gram.

 

Question- 4 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: Before growing a crop, a farmer first prepares the soil of the field. During preparation, he turns the soil by the help of plough or a cultivator and loosens it. Loosening of soil allows the new germinating roots of the plants to penetrate deep into the soil. The loose soil also facilitates easy breathing to the roots even when they go deep into the soil. The loosened soil helps in the growth of earthworms and microbes present in the soil which 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: After soil preparation, the farmer’s next job is to sow the seeds. First, good quality and high yielding seeds are selected. Seeds are sown with the help of a tool called seed drill. This tool facilitates the sowing of seeds uniformly at proper distances and depths and saves time and labour. It ensures that seeds get covered by the soil after sowing. This prevents damage caused by birds.

c) Weeding: The undesirable plants that grow naturally along with the main crop planted are called weeds. These weeds compete with the main crop plant for water, nutrients, sunshine and space. Weeds can be controlled by weeding. Weeding is the removal of weeds from the field. Weeding can be done by tilling and by using weedicides. Some weeds interfere even in harvesting and may be poisonous for animals and human beings.

d)Threshing: After harvesting a crop, its grain seeds need to be separated from the chaff. This process of separation of grain seeds from chaff is called threshing. This is done with the help of a machine called combine which is in fact a combined harvester and a thresher.


Question- 5 Explain how fertlisers are different from manure.

Answer:

Fertiliser

Manure

It is a chemical substance which is rich in particular nutrients.

It is a natural substance acquired by the decomposition of organic waste such as cattle dung, human waste and plant residues.

 

It decreases the soil fertility.

It increases the fertility of soil by replenishing the nutrients.

It does not provide any humus to the soil.

It provides a lot of humus to the soil.

It is very rich in nutrients like nitrogen, phosphorus and potassium.

It is relatively less rich in plant nutrients.

It is responsible for soil and water pollution.

It does not cause soil and water pollution.


Question- 6 What is irrigation? Describe two methods of irrigation which conserve water.

Answer: Irrigation is a process by which water is supplied to crops. The time and frequency of irrigation depends on the seasons, crops and soil types.

Two methods of irrigation that help in conservation of water are:

  • Sprinkler system: in this system perpendicular pipes with rotating nozzles on top are joined to the main pipe at regular intervals. With the help of a pump water is allowed to flow through main pipe under high pressure. From the main pipes the water escapes outside through the rotating nozzles. This system works efficiently in sandy soil where sufficient water is not available.
  • Drip irrigation: In this system, water is dropped at the root of the plants, drop by drop. Water is not wasted in this type of irrigation and this method is used for watering fruit plants and gardens.


Question- 7 If wheat is sown in the kharif season, what would happen? Discuss.

Answer: If wheat is sown in the kharif season (from June to October), it has to face adverse climatic conditions and the entire wheat crop might get destroyed. Wheat is a rabi crop. Therefore, it requires low temperature, less humidity, less water and moderate sunshine. But if it is sown in kharif season, it would receive lot of water, excess temperature, and humidity. These climatic conditions would not favour the growth of the crop.

Question- 8 Explain how soil gets affected by the continuous plantation of crops in a field.

Answer: Continuous plantation of crops in a field causes depletion of certain nutrients like phosphorus, nitrogen and potassium etc. Plants are depended on these nutrients for their proper growth and functioning. Depletion of these nutrients from the soil would directly affect the yield of the crops sown in the depleted soil.


Questiom - 9 What are weeds? How can we control them?

Answer: The undesirable plants that grow naturally along with the main crop are called weeds. These weeds compete with the main crop plant for water, nutrients, sunshine and space. Weeds can be controlled by weeding. Weeding is the removal of weeds from the field. Weeding can be done by:

Tilling: In this method, the weeds are either manually uprooted or cut from soil. The uprooted and cut weeds are then left in the field so that they would decay and act as the manure.

Using weedicides: In this method, certain chemicals called weedicides such as 2, 4-D are sprayed on the fields to kill the weeds. Weedicides are used during the vegetative growth of weeds.

Question - .10 Arrange the following boxes in proper order to make a flow chart of sugarcane crop production.

image

Answer :-

image


Q.11 Complete the following word puzzle with the help of 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 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 chaff.

Answer
Down

1. IRRIGATION
2. STORAGE
5. CROP

Across
3. HARVESTOR
4. GRAM
6. WINNOWING


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