Book Reading Science Power
class 8th SRIJAN publications
Answer: Cotton or rice cannot be grown in winter as
they require lot of water where as wheat
cannot be grown in rainy seasons as they need much less rain and low
temperature.
Check point
-01[Formative]
Q. Why cotton or rice cannot be grown in winter or wheat
in rainy seasons?
Answer: Cotton or rice cannot be grown in winter as
they require lot of water where as wheat
cannot be grown in rainy seasons as they need much less rain and low
temperature.
Q. Name the main cereal crops grown in India?
Answer:
Rice, wheat, maize etc. are the main cereal crops grown in India.
Q. Name the crops seasons in India .Why do we have
different crops seasons?
Answer:
Rainy season(Kharif crops) and winter season (Rabi crops)are two main crops
seasons in India. We have different crops seasons as different crops required
different climatic conditions like temperature, humidity and rainfall.
Q. Give reason why Kharif crops cannot be grown in Rabi
season?
Answer:
Kharif crops cannot be grown in Rabi season because they need lot of water.
Q. Name three crops plants grown in Kharif seasons.
Answer: Paddy, maize, bajra.
Q. What are the important aspects of
getting a bumper crops?
Answer: Following are the important aspects of getting a bumper
crops:
(i) Preparation of
soil
(ii) selection and sowing seeds (iii) Adding manure and fertilizers
(ii) selection and sowing seeds (iii) Adding manure and fertilizers
(iv) Irrigation (v) Protecting
from weeds, pets and diseases
(VI) Harvesting (vii) Storage
(VI) Harvesting (vii) Storage
Q. Give two advantage of plowing field?
Answer: The two advantage of plowing field are:
(i) to allow the roots to penetrate deep into the soil
(i) to allow the roots to penetrate deep into the soil
(ii) To increase the growth of earthworms and microbes in soil
Q. Why is leveling essential?
Answer: leveling essential
(i) to prevent the loss of moisture from ploughed field
(ii) to prevent water logging in field (iii) to prevent loss of the upper layer of soil
(i) to prevent the loss of moisture from ploughed field
(ii) to prevent water logging in field (iii) to prevent loss of the upper layer of soil
Check
point -02[Formative]
Q. Why we need to keep proper distance
between seeds?
Answer: This help to get enough sunlight, water and nutrients by
preventing overcrowding in field.
Q. Name the three steps involve in soil
preparation.
Answer: The three steps involve in soil preparation are
ploughing, levelling and manuring.
Q.
Name the medium in which plants grow.
Answer:
Soil is the medium in which plants grow.
Q.
Why is ploughing is essential. Give two reasons?
Answer:
Ploughing is essential for turning and loosening the soil and increase water holding
capacity.
Q. Sowing with seed drill is better. Give
two reasons?
Answer: Seed drill sows the seeds uniformly at proper distances
and depths. It ensures that seeds get covered by the soil after sowing. A seed
drill also saves time and labor.
Q. What is transplantation?
Answer: The practice of transferring seedling from nursery to
main field is called transplantation.
Check point
-03[Formative]
Q. Name the two fertilizers containing nitrogen and
other containing phosphorous?
Answer:
The two fertilizers containing nitrogen are urea(CH4N2O)
and ammonium sulphate [(NH4)2SO4] and The two
fertilizers containing phosphorous are ammonium hydrogen Phosphate and ammonium Phosphate [(NH4)2HPO4]
Q. How is compost prepared?
Answer:
compost is prepared from the decomposition of vegetable waste, farm and kitchen
waste by the action of soil bacteria.
Q. What are bio fertilizers?
Answer:
A biofertilizer is a substance which contains living microorganisms like
Azobacter and micorrhiza.
Q. What is the use of field fallowing?
Answer:
fallowing means leaving field to rest for a season this helps to improve soil
fertility.
Q. Explain the significance of crop rotation or mixed
cropping?
Answer:
The practice of growing different crops alternately in a field is called crop
rotation like pulses that are grown between two cereals. The practice of
growing two or more types of crops in the field is called mixed cropping. These
help in the replenishment of the soil with nutrients.
Check point -04[Formative]
Q. Why fields need to be irrigated before sowing seeds?
Answer:
To maintain moisture in soil for seed germination
Q. Why should seeds be shown in moist soil?
Answer:
Moist soil helps in proper germination and growth of seeds.
Q. Why drip irrigation is better than other method of
irrigation?
Answer:
This is because, in drip system, the water falls drop by drop just at the
position of the roots and there is no wastage of water. It is a boon in the
regions where availability of water is poor.
Q. Why excessive irrigation harmful to the crops?
Answer:
Excessive irrigation cuts off oxygen supply to roots of plants that prevent
proper growth of plants. Excessive irrigation also increase amount of salt in
soil that reduces fertility of soil.
Check point -05[Formative]
Q. What are weeds? How do they effect crops?
Answer:
The undesirable plants that
grown naturally along with the crop in a field are called weeds. For example: Amaranthus,
Wild Oat (javi), Chenopodium (bathua). Weeds compete with the crop plants for
water, nutrients, space and light. Thus, they affect the growth of the crop.
Q. Give one difference and one similarity between weedicides and insecticides?
Answer:
weedicides kill weeds where as insecticides
kill insects. Both weedicides
and insecticides are sprayed standing crops before flowering and fruiting.
Q. Differentiate between insecticides and pesticides?
Answer:
insecticides kill insects where as pesticides kill pests and their eggs.
Q. Name the methods used for pest eradication.
Answer:
By chemical control and by biological control
Q. What are the harmful effects of using insecticides or
pesticides?
Answer:
Insecticides and pesticides contain very harmful chemicals which cause harmful
effect on human health, pollute soil and water and also kill useful insects.
Q. What is organic farming? Why should we opt for it?
Answer:
The method of farming in which organic manure and biological methods for
controlling pets are used is called organic farming. We opt for it to reduce effect of chemical
fertilizer on the soil.
Check point -06[Formative]
Q. How is cross breading carried out in plants?
Answer:
At first anthers are removed [Emasculation] from one plant and pollen grain of
another flower are transferred to stigma of first flower and covered with
plastic bag till seeds formed.
Q. What is harvesting?
Answer: The cutting and gathering of crops after it
is matured is called harvesting.
Q. Give the name of two crops harvested manually.
Answer:
Rice and wheat
Q. Name the machine used for both harvesting and
threshing.
Answer:
combine
Q. Name the process of separating grain from harvested
crops.
Answer: Thressing
Answer: Thressing
Q. Why is threshing essential?
Answer:
This is because threshing separates grain and husk from harvested crops.
Q. What do you mean by green revolution?
Answer:
The combined efforts that result in increase in food production by using new
techniques that made our country self sufficient in food grain production is
called green revolution.
Q. Name the scientist whose efforts resulted in the
success of green revolution.
Answer:
M.S. Swaminathan
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