Case Study Based Questions: Crop Production and Management | Science Class 8 PDF Download

Case study 1

When plants of the same kind are cultivated at one place on a large scale, it is called a crop. For example, crop of wheat means that all the plants grown in a field are that of wheat. You already know that crops are of different types like cereals, vegetables and fruits. These can be classified on the basis of the season in which they grow. India is a vast country. The climatic conditions like temperature, humidityand rainfall vary from one region to another. Accordingly, there is a rich variety of crops grown in different parts of the country. Despite this diversity, two broad cropping patterns can be identified. These are:(i) Kharif Crops: The crops which are sown in the rainy season are called kharif crops. The rainy season in India is generally from June to September. Paddy, maize, soya bean, groundnut and cotton are kharif crops.(ii) Rabi Crops: The crops grown in the winter season (October to March) are called rabi crops. Examples of rabi crops are wheat, gram, pea, mustard and linseed. Besides these, pulses and vegetables are grown during summer at many places.

Q1: Soya bean which is generally sown from June to September is an example of ……………………….. crops.
(a) Kharif
(b) Zaid
(c) Rabi
(d) Fiber
Ans: (a)

Q2: Which of the following mentioned crop is included in the category of Rabi Crop?
(a) Paddy
(b) Cotton
(c) Groundnut
(d) Mustard
Ans: (d)

Q3: Which among the following factors or conditions does NOT affect the crop production?
(a) Temperature
(b) Humidity
(c) Literacy
(d) Rainfall
Ans: (c)

Q4: What do you understand by the term “Crop”?
Ans: When plants of the same kind are cultivated at one place on a large scale in order to provide food for a large population, it is called a crop.

Q5: What are Rabi Crops? Enlist some of the examples of Rabi Crops.
Ans: Rabi crops are grown in the winter season, mainly from October to March. Examples of Rabi crops include wheat, gram, pea, linseed, and mustard.

Case study 2

The preparation of soil is the first step before growing a crop. One of the most important tasks in agriculture is to turn the soil and loosen it. This allows the roots to penetrate deep into the soil. The loose soil allows the roots to breathe easily even when they go deep into the soil. Why does the loosening of soil allow the roots to breathe easily? The loosened soil helps in the growth of earthworms and microbes present in the soil. These organisms are friends of the farmer since they further turn and loosen the soil and add humus to it. But why the soil needs to be turned and loosened? You have learnt in the previous classes that soil contains minerals, water, air and some living organisms. In addition, dead plants and animals get decomposed by soil organisms. In this way, various nutrients in the dead organisms are released back into the soil. These nutrients are again absorbed by plants. Since only a few centimetres of the top layer of soil supports plant growth, turning and loosening of soil brings the nutrient-rich soil to the top so that plants can use these nutrients. Thus, turning and loosening of soil is very important for cultivation of crops. The process of loosening and turning of the soil is called tilling or ploughing. This is done by using a plough. Ploughs are made of wood or iron. If the soil is very dry, it may need watering before ploughing. The ploughed field may have big clumps of soil called crumbs. It is necessary to break these crumbs. Levelling the field is beneficial for sowing as well as for irrigation. Levelling of soil is done with the help of a leveller. Sometimes, manure is added to the soil before tilling. This helps in proper mixing of manure with soil. The soil is moistened before sowing.

Q1: Which of the following organisms is widely known as the friends of farmers?
(a) Cow
(b) Earthworm
(c) Dog
(d) Cockroach
Ans: (b)

Q2: The process of loosening and turning of soil is commonly termed as ……………………………...
(a) Watering
(b) Winnowing
(c) Ploughing
(d) Harvesting
Ans: (c)

Q3: Why is manure sometimes added to the soil before the process of tilling?
(a) For proper mixing of manure in soil
(b) To reduce the workload
(c) To disinfect soil
(d) For leveling properly
Ans: (a)

Q4: Explain in detail the importance of turning the soil and loosening it.
Ans: Turning of soil allows roots to penetrate deep into the soil. This loosening allows roots to breathe easily. Turning and loosening also helps in the growth of earthworms and microbes present in soil.

Q5: How is leveling of the soil done? What is the benefit of leveling?
Ans: Leveling of soil is done using a leveler or a similar tool. It helps in even distribution of water and prevents soil erosion. Proper leveling also ensures that seeds are sown at a uniform depth.

Case study 3

Before sowing the seeds, it is necessary to break soil clumps to get better yield. This is done with the help of various tools. The main tools used for this purpose are the plough, hoe and cultivator. Plough: This is being used since ancient times for tilling the soil, adding fertilisers to the crop, removing the weed sand turning the soil. This is made of wood and is drawn by a pair of bulls or other animals (horses and camels). It contains a strong triangular iron strip called ploughshare. The main part of the plough is a long log of wood which is called a plough shaft. There is a handle at one end of the shaft. The other end is attached to a beam which is placed on the bulls’ necks. One pair of bulls and a man can easily operate the plough. The indigenous wooden plough is increasingly being replaced by iron ploughs now a days. Hoe: It is a simple tool which is used for removing weeds and for loosening the soil. It has a long rod of wood or iron. A strong, broad and bent plate of iron is fixed to one of its ends and works like a blade. It is pulled by animals Cultivator: Nowadays ploughing is done by tractor-driven cultivator. The use of cultivator saves labour and time. 

Sowing is an important part of crop production. Before sowing, good quality, clean and healthy seeds of a good variety—are selected. Farmers prefer to use seeds which give high yield.

Are there seeds which float on water? Would those be lighter or heavier than those which sink? Why would they be lighter? Damaged seeds become hollow and are thus lighter. Therefore, they float on water. This is a good method for separating good, healthy seeds from the damaged ones. Before sowing, one of the important tasks is to know about the tools used for sowing seeds. Traditional tool: The tool used traditionally for sowing seeds is shaped like a funnel. The seeds are filled into the funnel, passed down through two or three pipes having sharp ends. These ends pierce into the soil and place seeds there. Seed drill: Nowadays the seed drill is used for sowing with the help of tractors. This sows the seeds uniformly at equal distance and depth. It ensures that seeds get covered by the soil after sowing. This protects seeds from being eaten by birds. Sowing by using a seed drill saves time and labour. Appropriate distance between the seeds is necessary to avoid overcrowding of plants. This allows plants to get sufficient sunlight, nutrients and water from the soil. At times a few plants may have to be removed to prevent over crowding.

Q1: Which one of the following equipment is NOT used for the purpose of tilling of soil?
(a) Plough
(b) Hoe
(c) Cultivator
(d) Hammer
Ans: (d)

Q2: ……………………… is used to sow seeds uniformly at equal distance and depth?
(a) Sickle
(b) Spade fork
(c) Seed drill
(d) Rake
Ans: (c)

Q3: What is the most important thing to be done before sowing of the seeds?
(a) Tilling
(b) Seeding
(c) Harvesting
(d) Threshing
Ans: (a)

Q4: What needs to be taken care of before the process of sowing?
Ans: Things to be taken care of before sowing are to select good quality, clean, and healthy seeds of good variety. It is also important to select the seeds which give high yield.

Q5: Explain a method to determine the damaged seeds before sowing.
Ans: To determine damaged seeds, they are put in a vessel containing water. Some seeds will float and some seeds will sink. The seeds floating are lighter because they are hollow from inside. Thus, damaged seeds can be separated from good quality seeds.

Case study 4

The substances which are added to the soil in the form of nutrients for the healthy growth of plants are called manure and fertilisers. Soil supplies mineral nutrients to the crop plants. These nutrients are essential for the growth of plants. In certain areas, farmers grow crop aftercrop in the same field. The field is never left uncultivated or fallow. Imagine what happens to the nutrients? Continuous cultivation of crops makes the soil poor in nutrients. Therefore, farmers have to add manure to the fields to replenish the soil with nutrients. This process is called manuring. Improper or insufficient manuring results in weak plants. Manure is an organic substance obtained from the decomposition of plant or animal wastes. Farmers dump plant and animal waste in pits at open places and allow it to decompose. The decomposition is caused by some microorganisms. The decomposed matter is used as organic manure. Fertilisers are chemicals which are rich in a particular nutrient. How are they different from manure? Fertilisers are produced in factories. Some examples of fertilisers are— urea, ammonium sulphate, superphosphate, potash, NPK (Nitrogen, Phosphorus, Potassium). The use of fertilisers has helped farmers to get better yield of crops such as wheat, paddy and maize. But excessive use of fertilisers has made the soil less fertile. Fertilisers have also be come a source of water pollution. Therefore, in order to maintain the fertility of the soil, we have to substitute fertilisers with organic manure or leave the field uncultivated(fallow) in between two crops. The use of manure improves soil texture as well as its water retaining capacity. It replenishes the soil with nutrients. Another method of replenishing the soil with nutrients is through crop rotation. This can be done by growing different crops alternately. Earlier, farmers in northern India used to grow legumes as fodder in one season and wheat in the next season. This helped in the replenishment of the soil with nitrogen. Farmers are being encouraged to adopt this practice.

In the previous classes, you have learnt about Rhizobium bacteria. These are present in the nodules of roots of leguminous plants. They fix atmospheric nitrogen. Advantages of Manure: The organic manure is considered better than fertilisers. This is because:

• it enhances the water holding capacity of the soil.
• it makes the soil porous due to which exchange of gases becomes easy.
• it increases the number of friendly microbes.
• it improves the texture of the soil.

Q1: Organic substance obtained from the decomposition of plant and animal waste that helps in the healthy growth of plants are called:
(a) Fertilisers
(b) Chemicals
(c) Manure
(d) Cow dung
Ans: (c)

Q2: Excessive use of fertilisers is generally observed to ………………………………?
(a) Decrease the fertility of soil
(b) Increase the soil content
(c) Rise the amount of microbes
(d) Rise the amount of water in soil
Ans: (a)

Q3: Which of the following nitrogen-fixing bacteria is present in the root nodules of leguminous plants?
(a) E. coli
(b) Rhizobium bacteria
(c) Archaebacteria
(d) Eubacteria
Ans: (b)

Q4: Write down some of the examples of commonly used fertilisers.
Ans: Some examples of fertilisers include super phosphate, potash, NPK (Nitrogen, Phosphorus, Potassium), urea, and ammonium sulphate.

Q5: What do you understand by the term “crop rotation”? Give its importance.
Ans: Crop rotation is the process of growing different crops alternately. It is important because it replenishes the soil with nutrients.

Case study 5

All living beings need water to live. Water is important for proper growth and development. Water is absorbed by the plant roots. Along with water, minerals and fertilisers are also absorbed. Plants contain nearly 90%water. Water is essential because germination of seeds does not take place under dry conditions. Nutrients dissolved in water are transported to each part of the plant. Water also protects the crop from both frost and hot air currents. To maintain the moisture of the soil for healthy crop growth, fields have to be watered regularly. The supply of water to crops at regular intervals is called irrigation. The time and frequency of irrigation varies from crop to crop, soil to soil and seas onto season. In summer, the frequency of watering is higher. Why is it so? Could it be due to the increased rate of evaporation of water from the soil and the leaves? Sources of irrigation: The sources of water for irrigation are— wells, tube wells, ponds, lakes, rivers, dams and canals. Traditional Methods of Irrigation The water available in wells, lakes and canals is lifted up by different methods indifferent regions, for taking it to the fields. Cattle or human labour is used in these methods. So these methods are cheaper, but less efficient. The various traditional ways are: (i) moat (pulley-system)(ii) chain pump(iii) dhekli, and(iv) rahat (Lever system).Pumps are commonly used for lifting water. Diesel, biogas, electricity and solar energy is used to run these pumps. Modern Methods of Irrigation Modern methods of irrigation help us to use water economically.

The main methods used are as follows:(i) Sprinkler System: This system is more useful on the uneven land where sufficient water is not available. The perpendicular pipes, having rotating nozzles on top, are joined to the main pipeline at regular intervals. When water is allowed to flow through the main pipe under pressure with the help of a pump, it escapes from the rotating nozzles. It gets sprinkled on the crop as if it is raining. Sprinkler is very useful for lawns, coffee plantation and several other crops(ii) Drip system: In this system, the water falls drop by drop directly near the roots. So, it is called drip system. It is the best technique for watering fruit plants, gardens and trees. Water is not wasted at all. It is a boon in regions where availability of water is poor.

Q1: Which of the following is NOT an example of a source of irrigation?
(a) Well
(b) Forest
(c) Canal
(d) Dams
Ans: (b)

Q2: Which one of the following examples is a traditional method of irrigation?
(a) Sprinkler
(b) Drip system
(c) Hose
(d) Dhekli
Ans: (d)

Q3: …………………. is used in uneven land where sufficient water is not available and has a rotating nozzle?
(a) Sprinkler system
(b) Pulley system
(c) Drip system
(d) Chain pump system
Ans: (a)

Q4: Why is irrigation important in crop cultivation?
Ans: Irrigation is the process of supplying water to crops at regular intervals. Irrigation is important for the proper growth and development of the plants. Along with water, irrigation also helps absorb minerals and fertilizers and aids in the germination of seeds.

Q5: Explain in detail about the drip irrigation system.
Ans: In the drip irrigation system, water falls drop by drop directly near the roots. It is considered to be the best technique for watering fruit plants, gardens, and trees. It reduces wastage of water and is ideal for places with poor availability of water.