Crop Production and Management ( Science Class - 8)

Subject – Science        Class - 8

Chapter b- 1 : Crop Production and Management

Exercise

Question 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_crop_.

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

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

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

 

 

Question 2. Match items in column  A  with those in column  B.

A	B
(i)                 Kharif crops	Paddy and maize
(ii)                Rabi crops	Wheat,gram,pea
(iii)             Chemical fertiliser	Urea and super phosphate
(iv)              Organic manure	Animal excreta, cow dung urine and  plant waste
(v)               hay	Food for cattle

 

Question 3. Give two examples of  each.

(a)  Kharif  crop

(b)  Rabi  crop

 

Answer- (a) Kharif crop - Paddy, Maize.

(b) Rabi crop - Wheat, Mustard.

 

 

Question 4. Write  a paragraph in your own words on each of the  following.

 

(a) Preparation of soil - 

 The upper layer of earth is called soil. The crop plants are grown in soil. Soil provides minerals, water,air, humus and anchorage (fixing firmly), to the plants. Preparation of soil is the first step in cultivating a crop for food production. The soil is prepared for sowing the seeds of the crop by (i) ploughing, (ii) levelling, and (iii) manuring. Each one of these steps has its own significance. 

(b) Sowing –

 Once the soil in the field has been prepared by ploughing, levelling and manuring, etc., seeds of the crop can be sown in it. The process of scattering seeds (or putting seeds) in the ground soil for growing the crop plants is called sowing. Sowing is the most important part of crop production. Before sowing, good quality seeds are selected. Good quality seeds are clean and healthy seeds free from infection anddiseases. Farmers prefer to use seeds which give high yield of food grains.

Seeds are sown in the soil either by hand or by seed drill

(c) Weeding –

The unwanted plants (or wild plants) which grow alongwith a cultivated crop are called weeds. The process of removing weeds (unwanted plants) from a crop field is called weeding.The best time for the removal of weeds is before they produce flowers and seeds. Weeding is done by hand or with the help of implements like trowel (khurpa). Weeds can also be destroyed (or controlled) by spraying special chemicals called weedicides in the crop fields.

(d) Threshing –

The process of beating out the grains from the harvested crop plants is called threshing. Threshing is done to take out the grain from its outer covering called chaff. In the traditional method of threshing, the harvested crop is spread on the ground in a smallarea and various cattle like bullocks, buffaloes and camels are made to walk over it again and again in a circle. The cattle’s feet crush the harvested crop plants due to which the chaff breaks up and the grain comes out. During threshing, the leaves and stems of the crop plants are converted into very small pieces called hay which is used as a fodder for animals. In larger farms, a motorised machine called thresher is also used for the threshing process.

 

Question 5. Explain how fertilisers are different from manure.

Answer - Differences between Manures and Fertilisers

 

Manure	Fertiliser
1.     1.  A manure is a natural substance obtained by the decomposition of animal wastes like cow dung, human waste, and plant residues.	1.    1.   A fertiliser is a salt or an organic compound.
2.    2.   A manure is not very rich in essential plant nutrients like nitrogen, phosphorous and potassium.	2.Fertiliser are very rich in plant nutrients like nitrogen, phosphorous and potassium.
3.     3.  A manure provides a lot of organic matter like humus to the soil.	3 .A fertiliser does not provide any humus to the soil
4.   4.    A manure is absorbed slowly by the plants because it is not much soluble in water.	4 .Being soluble in water, a fertiliser is readily absorbed by the plants.
5.    5.   A manure can be prepared in the fields.	5 . Fertilisers are prepared in factories.

 

 

 

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

Answer - The process of supplying water to crop plants in the fields is called irrigation. 

The modern methods of irrigation help us to use water economically (by preventing its wastage). The two main modern methods of irrigation are :

(i) Sprinkler system, and

(ii) Drip system.

(i)                 SPRINKLER SYSTEM-

In the sprinkler system of irrigation, a main pipeline is laid in the fields. Perpendicular pipes having rotating nozzles at the top are joined to the main pipeline at regular intervals. When water from a tube-well is allowed to flow through the main pipeline under pressure with the help of a pump, it escapes from the rotating nozzles. This water gets sprinkled on the crop plants as if it is raining. The sprinkler system of irrigation is more useful for the uneven land where sufficient water is not available. The sprinkler system is also very useful for sandy soil.

 

(ii)               DRIP SYSTEM.

In the drip irrigation system, there is a network of narrow pipes (or tubes) with small holes, in the fields. When water flows through the narrow pipes, it falls drop by drop at the position of roots of the plants. This water is absorbed by the soil in the root zone of the plants and utilised by the plants. There is no run-off (or wastage) of irrigation water. Drip system is the best technique for watering (or irrigating) fruit plants, trees and gardens. Drip irrigation system has the following advantages :

(i) Drip system provides water to plants drop by drop. So, water is not wasted at all.

(ii) Drip system minimises the use of water in agriculture. So, drip system of irrigation is very useful in those regions where the availability of water is poor.

 

 

 

Question 7. If wheat is sown in the  kharif  season, what would happen? Discuss.

Answer - If wheat is sown in the kharif season, it will not grow well. This is because wheat plants cannot tolerate too much water of the rainy season.

 

 

 

 

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

Answer - The fertility of soil can be improved by crop rotation. The practice in which different types of crops (leguminous crops and non-leguminous crops) are grown alternately in the same field or soil is called crop rotation. In crop rotation, the cereal crops like wheat, maize, paddy and millet are grown alternately with leguminous crops like pulses, peas, beans, groundnut and clover, etc., in the same field. Rotation of crops has the following advantages :

(i) Rotation of crops improves the fertility of the soil by replenishing it with nitrogen and hence brings about an increase in the production of food grains.

(ii) Rotation of crops saves a lot of nitrogenous fertiliser. This is because the leguminous crops grown during the rotation of crops can fix atmospheric nitrogen with the help of their nitrogen fixing bacteria, and there is no need to add nitrogenous fertiliser to the soil.

 

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

Answer - . The unwanted plants (or wild plants) which grow alongwith a cultivated crop are called weeds. The growth of weeds in the fields is harmful because they consume a lot of fertiliser, water, sunlight and space, meant for the crop plants and reduce the crop yield, and lower the quality of food grains. Since the presence of weeds in the fields will reduce the crop-yield, therefore, it is necessary to remove them from time to time. 

The process of removing weeds (unwanted plants) from a crop field is called weeding.  Thus, the various methods of weeding (controlling weeds or eradicating weeds) are as follows :

1. Removal of Weeds by Pulling Them Out With Hand. Weeds can be removed from the crop fields just by pulling them up with hands. When we pull the weeds, they get uprooted from the field. These uprooted weeds can then be thrown away.

2. Removal of Weeds by Using a Trowel (Khurpa). Weeds can be removed by digging or cutting them close to the ground from time to time with the help of an implement called trowel (or khurpa). 

3. Destroying the Weeds by Spraying Special Chemicals Called Weedicides. The poisonous chemicals which are used to kill weeds (unwanted plants) in the fields are called weedicides. Some of the common weedicides are : 2,4-D, MCPA and Butachlor. A solution of the weedicide in water is sprayed on the standing crops in the fields with a sprayer. The weedicides kill (destroy) the weeds (unwanted plants) but do not damage the main crop.