Wednesday, May 2, 2012

Class 8 - Science - Ch1 - Crop Production and Management

FKFNYKBC8D7Q

NCERT Solutions


Q1: Select the correct word from the following list and fill in the blanks.
float, water, crop, nutrients, preparation.


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 crops is __preparation____ of the soil.

(c) Damaged seeds would __float___ on top of water.

(d) For growing a crop, sufficient sunlight and __water___ and __nutrients___ from the soil are essential.


Q2.Explain the difference between the thermoplastic and thermosetting plastics.
A 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
Answer: 1(e), 2(d), 3(b), 4(c)


Q3: Give two examples of each.
(a) Kharif crop
(b) Rabi crop


Answer:
(a) Kharif Crop: Paddy and maize.
(b) Rabi Crop: Wheat and gram.


Q4: 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 : The very basic but the most important step for getting the best harvest is the preparation of soil. The first step in the preparation of soil is loosening and turning of soil. This process is known as tilling or ploughing. The microorganisms in the soil decompose the dead plants and animals which add humus to the soil. Loosening brings the nutrients rich soil to the top and in this way the plants can easily absorb the nutrients available in the soil. Ploughing is done with the help of a plough which is made of iron or wood. The ploughed field is sometimes watered if the big pieces of soil are present in the soil. These big pieces are known as crumbs. The big pieces are break into small pieces and the land is leveled with the help of a leveler.

(b)Sowing: The most important part in crop production is sowing. Planting of seeds in the soil is known as sowing. This is done after ploughing the field. The important factor for good yield is the quality of seeds. Farmers usually prefer to use good quality of seeds that gives them good yield and high returns of their hardwork.
The different kinds of tools used for sowing are traditional tool and seed drill.

(c)Weeding: When the crops are sown some unwanted plants also grow naturally with these crops. These unwanted plants are known as weeds and the removal of weeds is known as weeding.
Weeding is important as weeds compete with the crop for water and light and it affects the growth of the crop.
The different ways of weeding are:
  1. Tilling: Tilling of fields before sowing the seeds uproots the weeds. Weeds then dry up and mixed with the soil.
  2. Manual removal: Weeds are removed manually with the help of trowel or harrow.
  3. Weedicides: There are certain chemicals available to control weeds which are known as weedicides. These are sprayed on the fields to kill the fields
(d)Threshing: After harvesting the grains are separated from the chaff. This is done manually or by a machine called thresher and the process for separating grains from the chaff is known as threshing. Sometimes in large fields a machine called combine is used which can do harvesting and threshing simultaneously.

Q5.Explain how fertilisers are different from manure.
Answer:

Fertilizers Manure
1 Fertilizers are made from chemicals and they are rich in plant nutrients like nitrogen, phosphorus etc. Manures are made from cattledung, human waste and plant residues. Manures are relatively less rich in plant nutrients as compared to fertilizers.
2 Fertilizers are prepared in factories. Manures are prepared in the fields.
3 Fertilizers do not provide any humus to the soil Manure provide a lot of humus to the soil.
4 Fertilizers pollute water as they are made from chemicals Manures do not pollute water as they are made from natural substances.

Q6.What is irrigation? Describe two methods of irrigation which conserve water.

Answer: The supply of water to crops at different intervals is known as irrigation.
The frequency of irrigation is different in different seasons. It also depends on the type of crop and the type of soil. In summers especially fields need to be irrigated at regular intervals.
There are different methods of irrigation. But the methods which conserve water are:


Sprinkler system:
In this system the main pipeline is joined with the perpendicular pipes at the regular intervals. These perpendicular pipes are attached with rotating nozzles on top. When water is allowed to flow the whole field is sprinkled with water as if it is raining. This is an effective method of irrigation. It is very useful in sandy soil. It also conserves water and very effective at the places where the rainfall is less an the availability of water is also less.

Drip system:
This system of irrigation is generally used to irrigate the gardens, trees and fruit plants. In this system the water falls drop by drop just at the position of roots. The places where water is not available in abundant, this method is very useful as the water is not wasted and the plants get regular supply of water.

Q7.If wheat is sown in the kharif season, what would happen? Discuss.

Answer: The sowing of wheat is done in winter season as the seeds of wheat need less water to germinate. And the wheat crop also needs less water as compared to the other crops. For wheat irrigation is needed only before tilling and at the time of flowering. If wheat is sown in the kharif season when there is abundant rainfall the water logging in the plants will reduce air in the soil spaces. As a result the seeds will not be germinated.

Q8: Explain how soil gets affected by the continuous plantation of crops in a field.
Answer: The crops grown in the fields consume lot of nutrients from the soil. If the crops are planted continuously, season after season all the nutrients and the minerals of the soil get exhausted. This affect the yield and it also affect the quality of soil. So the nutrients once consumed by a crop must be replenished so that the soil gets all its nutrients back and it will be ready for the next harvest. This is done by rotation of crops. The alternate plantation of leguminous plants replenishes the soil with all its important nutrients . By adding manures and fertilizers to the soil also improves the quality of soil.

Q9: What are weeds? How can we control them?
Answer: When the crops are sown some unwanted plants also grow naturally with these crops. These unwanted plants are known as weeds. Weeds compete with the crop for water and light and it affects the growth of the crop. There are some weeds which are harmful for plants and humans so they need compulsory removal. We can control the weeds by different methods.


Tilling: Tilling of fields before sowing the seeds uproots the weeds. Weeds then dry up and mixed with the soil.

Manual removal: Weeds are removed manually with the help of trowel or harrow.

Weedicides: There are certain chemicals available to control weeds which are known as weedicides. These are sprayed on the fields to kill the fields.

Q10: Arrange the following boxes in proper order to make a flow chart of sugarcane crop production.


Answer: The correct sequence is:
  1. Preparation of soil
  2. Ploughing the field
  3. Sowing
  4. Manuring
  5. Irrigation
  6. Harvesting
  7. Sending crop to sugar factory

Q11. Complete the following word puzzle with the help of clues given below.
Down
1. Providing water to the crops.-Irrigation
2. Keeping crop grains for a long time under proper conditions.- storage
5. Certain plants of the same kind grown on a large scale.-crop
Across
3. A machine used for cutting the matured crop.-harvestor
4. A rabi crop that is also one of the pulses.-gram
6. A process of separating the grain from chaff. -winnowing
Answer: 

Q12: Define the term 'Agriculture'
Answer: The science that deals with the growth of plants and animals for human use is called agriculture.

see MCQs on Crop Production and Management

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