NCERT Solutions for Class 8 Science Chapter 1 Crop Production And Management

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 ____________.

Answer :

(a) The same kind of plants grown and cultivated on a large scale at a place is called crop.

EXPLANATION :-
It means the same type of plants that is cultured using various tools, techniques and treatments using organic and inorganic nutrients during agriculture on a large field, this group of plant is called as crop.
For e.g., during rice cultivation, many rice plants are grown and cultivated together and thus rice plant is an example of crop. Similarly when a particular vegetable is grown in large quantity then it's plants are called as crop.
Other examples of crop are wheat plants, oats, millets, fruits etc.
Cultivation is the process of nurturing and nourishing the crops with manure which are organic compounds providing organic nutrients and fertilizers which are inorganic compounds providing inorganic nutrients.

(b)The first step before growing crops is ________ of the soil.

Answer :

(b)The first step before growing crops is preparation of the soil.

EXPLANATION:-
So the soil is first prepared to help in better growth of the crops. As we know that roots play a vital role in the proper growth of a plant/crop, so its necessary to make the soil ready before sowing of seeds.
Preparation of soil includes ploughing which gradually loosens the soil so that it can hold nutrients and water. These nutrients and water are transported to the crop through their roots.
Loosening of soil also helps the root to penetrate deep into the soil and help the soil microbes and earthworms to grow in the soil so that they can feed on plant debris(dead roots, leaves, grasses, manure). Their excreta contributes a lot for the nutrition of plants and when they decompose it further contributes to the nitrogen content of soil.

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

Answer :

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

EXPLANATION:-
Damaged seeds are hollow from inside. That means their inner content is either dried up due to harsh environmental conditions or is eaten up by the microbes. So the inner content becomes hollow and thus it gets lighter.
As we know that lighter particles float on water because of their low density hence damaged seeds float on water while the good seeds which have their full inner content settles at the bottom of the container in which water is present.

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

Answer :

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

EXPLANATION:-
Crop or plants needs sufficient sunlight because sunlight is the main source of energy in plants by which it performs photosynthesis. During the process of photosynthesis plants absorb light energy from sunlight and uses it to produce glucose(from glucose plants obtain their energy to perform various functions) and oxygen(as waste material it is excreted out) by converting carbondioxide and water in presence of chlorophyll.

Water is also an essential part that contributes in plant's growth by transporting nutrients and minerals from soil to each and every part of the plant. It also helps during photosynthesis process.

Nutrients are obtained by the plants through their roots from the soil. It helps the plant to withstand various diseases that occur due to deficiency of some nutrients and also to fight viral and bacterial diseases. Nutrients also helps the plant to yield flavorful and colorful fruits and flowers.

Q.2
Match items in column A with those in column B.
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 :

A B
(i) Kharif crops ----------------- (e) Paddy and maize
(ii) Rabi crops ------------------ (d) Wheat, gram, pea
(iii) Chemical fertilizers ----------(b) Urea and super phosphate
(iv) Organic manure--------------(c) Animal excreta, cow dung, urine and plant waste

EXPLANATION:-
Kharif crops are the monsoon crops whose seeds are sown around the end of May to early June and is harvested between October to November.

Rabi crops are the winter crops whose seeds are sown around mid of November and is harvested between April to May.

Chemical fertilizers are the single most contributor to the increase in world agricultural productivity. But chemical fertilizers affect adversely towards the soil fertility and also towards the microbes present in the soil.

Manure is organic in nature. Though it has a slow effect on the plants but it doesn't affect any environment negatively. It helps in soil enrichment as well as it makes the yield more fruitful.

Q.3. Give two example of each.
(a) kharif crops
(b) rabi crops

Answer :

(a) Kharif crops- paddy, maize
(b) Rabi crops- wheat, grams

EXPLANATION:-
Kharif crops are also called monsoon crops as their seeds are sown around end of May to early June and they are harvested between October to November.

Rabi crops are also called winter crops as their seeds are sown around the mid of November and they are harvested between April to May.

Q.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 first step before growing crops is preparation of the soil. So the soil is first prepared to help in better growth of the crops. As we know that roots play a vital role in the proper growth of a plant/crop, so its necessary to make the soil ready before sowing of seeds. Preparation of soil includes ploughing which gradually loosens the soil so that it can hold nutrients and water. These nutrients and water are transported to the crop through their roots. Loosening of soil also helps the root to penetrate deep into the soil and help the soil microbes and earthworms to grow in the soil so that they can feed on plant debris(dead roots, leaves, grasses, manure). Their excreta contributes a lot for the nutrition of plants and when their body decompose it further contributes to the nitrogen content of soil.

(b)Sowing:
Sowing is the process of scattering of seeds in an order, in or on the soil. Good quality seeds are used for sowing as it will help in a good yield. So there is pre-treatment of soil before sowing which includes seed cleaning with medium hot water for atleast 24 hours to upto 48 hours. Seed cleaning is done in case of fruits as the flesh around the fruits can make the seed prone to insect attack. Sowing is usually done with the help of either a traditional tool or a seed drill. The traditional tool is shaped like a funnel. Nowadays, seed drills that make the use of tractors are used for sowing seeds. This tool disperses seeds uniformly and sows seeds at a proper depth. Sowing by this method saves time and also protects the seeds from birds.

(c) Weeding:
Removal of unwanted plants from the field is called as weeding. Weeds compete with crop plants for nutrients and water. Thus it will reduce the yield of the desired crops. Weeds also interfere while harvesting and gets mixed with crops. Some weeds are poisonous to animals and humans. Tilling is a common method which helps in the removal of weeds before sowing crops which includes manual methods like physical removal of weeds. Weedicides are sprayed to get rid of weeds, but this method may affect the health of farmers because of the chemicals that are used in weedicides.

(d) Threshing:
The process of separating the chaff from the crop is known as threshing. It loosens the edible part of the grain from the straw to which it is attached. Threshing is carried out by a thresher. A machine called ‘combine’ which is a harvester that performs 4 separate harvesting functions that includes reaping, threshing, gathering and winnowing. Threshing is also done by winnowing where blow of wind is used to separate the chaff from crops.

Q.5 Explain how fertilisers are different from manure.

Answer :

FERTILIZERS:

1. Fertilizer is an inorganic substance
2. Fertilizers are prepared artificially using chemicals.
3. These are prepared in the factories.
4. They don't provide humus to the soil.
5. They are rich in plant nutrition like nitrogen, phosphorus, potassium.
6. They have adverse effects on soil fertility in the long run.


MANURE:

1. Manure is an organic substance.
2. Manure is obtained by decomposition of animal excreta, plant debris & human waste.
3. These are prepared in the field.
4. They provide humus to the soil.
5. They have relatively less plant nutrients.
6. Their long term usage improves soil fertility.

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

Answer :

The supply of water to crops at regular intervals is called irrigation. Methods of irrigation which conserve water are as follows :-

a) Drip Irrigation: The irrigation in which the water goes drop by drop directly into the roots. This is a type of micro-irrigation system in which water is allowed to drip slowly to the roots of plants either from above the soil surface or to the roots that is buried below the surface. Thus this process of watering plants minimizes evaporation of water. Hence this method is very useful as it conserves the water and also prevents us from irrigating the weeds.

b) Sprinkler Irrigation: This method is used mainly in 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. An irrigation sprinkler is used as a device for this type of irrigation. It is also used for cooling and for the control of airborne dust. Thus water from a sprinkler gets sprinkled on the crop as if it is raining.

Q.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), then the whole crop might get destroyed because of the following factors:-

1. Lack of optimum temperature:
The optimum temperature range for ideal germination of wheat seed is 20-25 degree Celsius. As there is frequent raining during the kharif season , so the wheat seeds might get damaged as the rain just after sowing can hamper germination process.
2. Adaptability:
Wheat grows in areas with low humidity to avoid diseases that it suffers in damp weather.
3. Availability of pests:
Appropriate pesticides and insecticides are used to control pests from affecting wheat.

Therefore, wheat crop should not be sown during kharif season.

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

Answer :

Plants require nutrients for their growth. Continuous plantation of crops results in depletion of certain nutrients like nitrogen, phosphorus, potassium. This results in the decrease of yield.

Nitrogen :
It is found in healthy soils, and give plants the energy to grow, and produce fruit or vegetables. Nitrogen is part of the chlorophyll molecule, which gives plants their green color and is involved in creating food for the plant through photosynthesis.

Phosphorus :
It is a constituent of plant cells, which is essential for cell division and development of the growing tip of the plant.

Potassium :
It is an essential element for plant growth and it is important to food crops. Potassium, often called potash, helps the plants to use water and resist drought conditions. It also enhances fruits and vegetables. If soluble potassium is deficient in soil it can result in stunt growth of plants and can also cause other symptomatic issues.

Thus deficiency of any of the nutrient can affect the crop adversely and hence to let the soil replenish its nutrition naturally there should be a gap between crops in order to get a good yield.

Q.9 What are weeds? How can we control them?

Answer :

Weeds are undesirable plants that affect the growth of plants surrounding them by competing for nutrients, soil, water, and space.

In cases of younger or smaller plants, some weeds even overpower their young plant parts. If left uncontrolled, weeds may become hosts for various plant diseases.

Weeds can be controlled using weedicides. It is a chemical, which is sprayed in the fields to kill all the available weeds.

Tilling before sowing of crops also helps in removing weeds. Tilling uproots the weeds.

The manual method of removing weeds is with the help of a "Khurpi".

Q.10 Arrange the following boxes in proper order to make a flow chart of sugarcane crop production.
1. Sending crops to sugar factory
2. Irrigation
3.Harvesting
4.Sowing
5.Preparation of soil
6.Ploughing the field
7.Manuring

Answer :

Flow chart of sugarcane crop production:

1. PREPARATION OF SOIL:

It helps to loosen the soil which allows the roots to penetrate deep into it. The loosening of the soil supports the growth of several soil microbes, earthworms which enrich the soil with humus and other essential nutrients.


2. PLOUGHING THE FIELD:

The prime purpose of ploughing is to turn over the uppermost soil, thus bringing fresh nutrients to the surface, while burying weeds and crop remains to decay.


3. SOWING:

The seeds are sown at the correct depth and correct interval. It gets covered by soil so that these seeds cannot be picked up and eaten by the birds. The seeds sown with a seed drill are in regular rows.


4. MANURING:

Manure is an organic matter that is used as organic fertilizer in agriculture. Most manure consists of animal excreta and other sources include compost and green manure.


5. IRRIGATION:

Irrigation is the artificial process of applying controlled amounts of water to land to assist in production of crops. Irrigation helps to grow agricultural crops, maintain landscapes, and revegetate disturbed soils in dry areas and during periods of less than average rainfall.


6. HARVESTING:

Harvesting is the process of gathering a ripe crop from the fields.


7. SENDING CROPS TO SUGAR FACTORY:

The crops are well stored and are transported to the factory.

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 from chaff.

Answer :

Down

1 . IRRIGATION
2 . STORAGE
5 . CROP
Across

3 . HARVESTOR
4 . GRAM
6 . WINNOWING