Class 8 science chapter 1 some more questions with answers

Q. 1. Is it necessary to remove weeds from the field time to time? Give reason.
Answer: Yes, it necessary to weed out unwanted plants time to time from crop field 
because it competes for space, nutrients and sunlight. It decreases the crop yield.
Q. 2. The government usually maintain a buffer stock of grains. Why
Answer: The government maintains buffer food stock in silos to provide food grain in 
case of food shortage due to disaster or natural calamity.
Q. 3. Write the advantage of using a cultivator.
Answer: Nowadays plowing on large scale is done by cultivator. A cultivator is a tractor￾driven machine. It cost effective and also saves time. The use of cultivator saves labour 
and time.
Q. 4. Organic foods are harmless. Do you agree?
Answer: The food which is grown organically is harmless and healthier because 
organic foods are grown without the use of chemical fertilizers and pesticides.
Q. 5. Write the name of the equipment which is used to level the tilled land.
Answer: Levelling of soil is done with the help of an equipment called leveller. Levelling 
beneficial for sowing as well as for irrigation.
Q. 6. Write the name of a man-made chemical substance that is rich in inorganic 
nutrients.
Answer: A man-made chemical substance is called fertilisers.
The fertilisers are the chemical substance which are rich in inorganic substance like 
urea, ammonium sulphate, NPK(Nitrogen, Phosphorus, Potassium ) etc.The use of 
fertilisers has helped farmers to get a better yield of crops like wheat, paddy and maize.
Q. 7. Which implement is used for harvesting?
Answer: Harvesting is carried out either by sickle or by a machine called Harvester.
Q. 8. Write two advantages of nitrogen fixation.
Answer: (a) Nitrogen-fixing bacteria fix atmospheric nitrogen in the root nodules of the 
leguminous plants without using fertilizers.
(b) It enhances soil fertility by adding nitrogenous compound such as nitrate to the soil. 
With this other crop also benefitted.
Q. 9. Explain the causes for the frequency of irrigation of crops being higher in 
the summer season.
Answer: During summer the frequency of watering of crops is higher because of the 
rate of evaporation of water from the soil and the leaves increases? To overcome 
intense heat the crop plants, require more water. Thus, the frequency of watering plants 
in summer is high.
Q. 10. A farmer was growing only paddy in a particular field for five successive 
generations. He found that the yield decreases every time. Give reasons and how 
can this problem be solved?
Answer: Growing of same type of crop in the same field for five successive 
generations, depletion of particular nutrients happen. This causes decrease in yield. 
This problem can be solved by planting two different crops alternately in the same field, 
one crop should be pulse crop. This is called crop rotation.
Q. 11. The harvested grains are stored without drying by a farmer. List the 
consequences.
Answer: The various consequence if the farmer stores freshly harvested grains are:
1. Freshly harvested grains contain more moisture. If freshly harvested grains (seeds) 
are stored without drying, grains get damaged leading to a loss in their germination 
capacity. 
2. Grains containing moisture can get attack by insects pest, bacteria and fungi.
Q. 12. Write four differences between threshing and winnowing.
Answer:
Q. 13. The use of fertilisers should be limited. Why?
Answer: • Fertilisers are chemicals, rich in a particular nutrient.
● Limited use of fertilizer increases crop yield.
● But excessive use of fertilisers is harmful to humans as well as other life and 
environment.
● Continuous use of fertilizer makes soil acidic and less fertile by removing nutrients 
from the soil.
● Fertilisers also cause water pollution, causes death of aquatic animals.
● Therefore, farmer should limit the use of chemical fertilizers in order to maintain the 
fertility of the soil.
Q. 14. Different crops are grown in different crop seasons. Explain this statement 
with examples.
Answer: ● Different crops require different temperaurte, moisture content and soil 
condition to grow.
● Our country has different seasons hence, different crops are grown.
● For examples crops like paddy, maize, sorghum, sugarcane, and pearl millets are 
sown in the months of June-July and harvested in September-October every year.
● Some crops such as wheat, oat, barley and pulses, oil seeds are sown in the months 
of October-November and harvested in the month March-April.
Q. 15. We use dried neem leaves for storing food grains. Explain.
Answer: Neem tree is native of India. Its leaves contain chemicals such as Nimbin 
which have antifungal, antibacterial property. Hence, dried neem leaves are used for 
storing food grains at home. Neem leaves kept in stored grain, protect from pests and 
microorganisms.
Q. 16. Differentiate between
(a) Rabi season crop and Kharif season crop.Q. 17. A gardener uses manure for better production, what is a manure? Describe 
the common types of manures. Give the advantages of using them.
Answer: ● The organic substances which are mixed to the soil for better growth of 
plants are called manure.
● Manure is an organic substance obtained from the decomposition of plant or animal 
wastes.
● Waste includes leaves, stems, other plant parts and dung from animals.
● For making manure plant and animal waste is dumped in pits at open places and 
allow it to decompose by microorganisms.
● The decomposed matter is the organic manure.
● Advantages of Manure:
(a) It adds humus and nutrients to the soil.(b) It enhances the water holding capacity of the soil.
(c) It makes the soil porous due to which exchange of gases becomes easy.
(d) It increases friendly microbes to the soil and improves its texture (content of the soil 
particles).
Q. 18. Threshing is an important agricultural practice. Explain what is it and how 
is it done.
Answer :
● It is a process which is carried out after harvesting.
● In this process of loosening of chaff from grains.
● It is done either traditionally or by modern machine.
● Traditionally it is done by striking harvested crop against hard surface or by beating 
the harvested crop with solid stick.
● Threshing is also carried out with the help of a machine called combine’ (combination 
of harvester and thresher).
Q. 19. What do you mean by weeds? Which methods do farmers use to remove 
weeds?
Answer: 
● Weeds are undesirable plants which are gown along with crop plants.
● Examples of weeds are bathua, chenopodium, chaulai.
● They compete with crop for space, nutrients and sunlight.
● Some weeds interfere even in harvesting and may be poisonous for animals and 
human beings.
● Hence, weeds are to be removed from the crop field.
● Farmers undertake many methods to remove weeds and control their growth(a) Tilling before sowing of crops helps in uprooting weeds and they get mixed with the 
soil after decomposition.
(b) Manual removal of weeds with the help of khurpi by uprooting or cutting them close 
to the ground from time to time.
(c) A seed drill is also used to uproot weeds.
(d) Weeds are also controlled by using certain chemicals called weedicides such as 2,4-
D are used to control weeds. Weedicides are sprayed in the fields to kill the weeds.
Q. 20. Write the traditional and modern methods used for irrigation.
Answer: Water is important for proper growth and development of the plants. Thus, the 
watering of crops at regular intervals is called irrigation. There are two methods of 
irrigation in India:
(a) Traditional Methods of Irrigation: in traditional methods water is lifted from water 
sources such as wells, lakes and canals by using human labour or cattle. Traditional 
methods are cheaper but less efficient. Examples of traditional methods moat (pulley￾system), chain pump, dhekli and rahat (Lever system). Pumps are commonly used for 
lifting water. Pumps run on fuels such as diesel, biogas, electricity and solar energy.
(b) Modern Methods of Irrigation:
Modern methods of irrigation help us to use water economically

(i) Sprinkler System: In this method perpendicular pipes with rotating nozzles at the end, 
are joined to the main pipeline at regular intervals. When water flows through the main 
pipe under pressure, water escapes from the rotating nozzles. It gets sprinkled on the 
crop as if it is raining.
(ii) Drip system: In this system, the water falls drop by drop directly near the roots of the 
plants, hence water is not wasted at all. It is the best technique for watering fruit plants, 
gardens and trees.

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