CBSE Class
8, ScienceCrop Production and Management
CBSE Class 8, ScienceCrop Production and Management
NCERT Answers of Science Chapter 1 Exercise Questions
Question.1: Select the
correct word from the following list and fill in the blanks:
a) The
same kind of plants grown and cultivated on a large scale at a place is called
_______.
b) The
first step before growing crops is ______of the soil.
c) Damaged
seeds would _____ on top of the water.
d) For
growing of crop, sufficient sunlight and ______and _____ from the soil are
essential.
Answer: (a) Crop (b) Preparation (c) Float
(d) Water, Nutrients.
Question.2: Match items in
column ‘A’ with those in column ‘B’:
(A)
|
(B)
|
i. Kharif
crops
ii. Rabi
Crops
iii. Chemical
Fertilizers
iv. Organic
Manure
|
a) Food
for cattle.
b) Urea
and super phosphate.
c) Animal
excreta, cow dung, urine & plant-waste.
d) Wheat,
gram, pea.
e) Paddy
and maize.
|
Answer: (i)-e (ii)-d (iii)-b (iv)-c
Question.3: Give two examples
of each: (a) Kharif crop, (b) Rabi crop.
Answer: (a) Paddy and maize (b) 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
The
preparation of soil is the first step before growing a crop. It includes the
process of loosening and turning of the soil called Tilling or Ploughing. It is
done by using ploughs, which are pulled by bulls. Tractor driven cultivators
are also used to till the soil. Tilling of the soils is important for following
reasons:
- This allows the roots to penetrate deep into the soil.
- This allows the root to breathe easily.
- The loosened soil helps in the growth of earthworms and microbes which further turn and loosen the soil and also help in adding humus to it.
- This process brings the nutrient rich soil to the top so that plants can use these nutrients.
(b) Sowing
Sowing is the most important part of the
crop production in which seeds are implanted in the prepared soil. Before
sowing only clean, healthy, good-variety and high yield seeds are segregated
and sowed in the fields. In the traditional method of sowing seeds, a long pipe
is used which has a funnel at its one end and the other end pierce into the
soil through which seeds are placed. Now a days a machine or a tool known as
seed drill is also used for sowing with the help of tractors. A seed drill
saves time & labour. While sowing the seeds care should be taken to
maintain proper distance and depth between the seeds to prevent damage of the
seeds caused by birds and also to prevent overcrowding of the plants.
(c) Weeding
Unwanted plants growing along the crops are
called weeds. The process of removal of weeds is called weeding. Weeding is
necessary since these weeds absorb the water, nutrients, space and light meant for
the crop plants. Weeding can be done manually with a ‘khurpi’ or mechanically
with the help of a ‘seed drill’ or even using certain chemical called
‘Weedicides’. The best period for weeding is during their vegetative phase
before flowering or bearing seeds.
(d) Threshing
When the crops are harvested they are cut
along with the stalks. They are then, separated and the grains are removed.
This process of separation of grains from the chaff is called ‘Threshing’. This
whole process is carried out with a machine called ‘Combine’ which is in fact a
combined harvester & thresher.
Question.5: Explain how
fertilizers are different from manure.
Answer: The differences between
fertilizers and manures are as follows:
- Fertilizers are chemical substances, while the manures are the organic substances (decay of plants & animal wastes).
- Fertilizers are prepared in the factories, while the manures are prepared in fields.
- Fertilizers don’t provide any humus to soil, while manures provide a lot of humus.
- Fertilizers are rich in plant nutrients like- Nitrogen, Phosphorus & Potassium but manures are less rich in plant nutrients.
- There are certain advantages of adding manure like-
a) It enhances the
water holding capacity of the soil,
b) It makes soil
porous due to which exchange of gases becomes easy.
c) It improves the
texture of soil and also increases the number of friendly microbes.
Question.6: What is
irrigation? Describe two methods of irrigation which conserve water.
Answer: Watering the crops in the fields
is called ‘irrigation’. Irrigation is done at different intervals. Irrigation
should be done in a way in which water does not get wasted. Different sources
of irrigation are like- wells, tube-wells, ponds, rivers. Two such methods
which conserve water are:
(i) Sprinklers: Sprinklers work like fountains. Long perpendicular
pipes having rotating nozzles on the top are joined to the main pipe lines at
regular distances. When water is supplied, it comes out of these rotating
nozzles which sprinkle water in all directions. Limited outflow of water, controls
wastage of water. This method is more suitable for uneven and sandy soil.
(ii) Drip System: This system allows the water to flow drop
by drop at the roots of the plants. It contains a main pipe which has further
lateral pipes containing small nozzles for the outflow of the water. Nozzles
are such placed that they throw water at the roots of the plants, which saves
water from flowing around uselessly. This technique is best suited for watering
fruit plants, gardens and trees where availability of water is poor.
Question.7: If wheat is sown
in kharif season, what would happen? Discuss.
Answer: If wheat is grown in kharif
season, they would not grow as they don’t need much water to grow. The seeds
would get destroyed in excess water due to rainy season.
Question.8: Explain how soils get affected by the continuous plantation of crops in a field.
Answer: Continuous plantation of crops
drains off the nutrients of the soil. It leaves the land unfertile and unable
to bear crop. It does not give any time to the soil to replenish the absorbed
nutrients by the crops, thus unable to sustain any further healthy and good crop.
Question.9: What are weeds?
How can we control them?
Answer: Weeds are the unwanted plants
growing along crops. They share the nutrients meant for plants and thus are
harmful for crop. We can control weeds with the help of chemicals Weedicides.
The removal of weeds is called weeding. They are either, removed manually or by
chemicals.
Manually this can be done with the help of
Khurpi or Seed-drill. Weedicides are sprayed in the fields to kill the unwanted
plants. These weedicides do not affect the main crop. Weeds are removed or
killed during their vegetative phase before flowering or bearing of seeds.
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