NCERT Grade 8-Crop Production and Management-Answers – MySchoolPage

NCERT Grade 8-Crop Production and Management-Answers

NCERT Solutions for Class 8 Science

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1.    Select the correct word from the following list and fill 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 crop.

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

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

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

2.    A          B

(i)        (e)

(ii)       (d)

(iii)      (b)

(iv)       (c)

3.    (a) Paddy and maize.

(b) Wheat and pea.

4.    (a) Preparation of soil:- It is the first step of before growing of crop in which soil is turned and loosen it. The softening of soil allows the deep penetration of roots into soil. The soil preparation includes ploughing, leveling and manuring. Ploughing is done with the help of plough or tractor. Leveling is done by leveler to make loosen soil smaller the even.

(b) Sowing: – The process of broadcasting seeds in soil to grow crop is called sowing. Sowing is done with the help of seed drill or broadcasting with hands. The healthy seed is selected for proper growth. The distance between seeds must be sufficient for proper growth.

(c) Weeding: – The unwanted plants that grow along with main crop and compete with crop for light, food and other substance are called weeds. Removal of these unwanted plants is called weeding. Weeding is done with hands of using chemicals called weedicides.

(d) Threshing: – In harvested crop, the grain seeds are separated from chaff. This process is called threshing. This is carried out by using a machine called combine. Threshed seed is winnowed to obtain clean seeds.

5.    Manure is an organic substance obtained from the decomposition of plant or animal wastes but fertilsers are inorganic substance prepared in factories. Fertilsers are rich in nutrients but manure has very less nutrients. Manure cannot harm the soil if used in greater quantity but fertilsers may harm the plants as well as soil. Manure is cheap and mostly prepared by farmers itself on the other hand fertilsers are costly and prepared in factories using chemicals.

6.   The supply of water to crops at different intervals is called irrigation. The time and frequency of irrigation differ from crop to crop, soil to soil and season to season. The main sources of irrigation are wells, tube wells, ponds, lakes, rivers, dams and canals. Irrigation is essential for proper growth of plants as without water no physiological activity is possible in living beings. The two methods of irrigation which conserve water are-

(a) Sprinkler system- This system is useful in uneven land where sufficient water is not available. The pipes having rotating nozzles on top are joined to regular interval. When water flows through this pipe at high pressure, nozzle throws water and sprinkle in all direction.

(b) Drip system- In this system water falls drop by drop just at the root. It is mainly used for watering fruit plants, gardens and trees. In this method water is not wasted at all. It is mainly used in water deficient areas.

7.    Kharif crops need lot of rainfall, whereas wheat needs winter season and not heavy rainfall. So, if wheat were sown in Kharif season, the crop will damaged due to heavy rainfall as well as collection of water in the field.

8.    Continuous growing of crops makes the soil poorer in certain nutrients. To avoid
this, a method of crop-rotation is adopted, which maintains the nutrients of the soil intact.

9.    The undesirable plants in the field are called weeds which have to be removed,
otherwise our own crop plants may not get sufficient water, nutrients, space and light. So, they are removed either by manual method or by using weedicides. The manual removal includes physical removal of weeds by uprooting or cutting them close to the ground from time to time. This is done with the help of a khurpi or harrow.

By using weedicides also, we can remove weeds. These weedicides only damage weeds and do not harm crops.

10.  

11.  

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