Lecture 5: CLASS VIII: SCIENCE: CHAPTER 1: HARVESTING

CLASS-VIII; SCIENCE

Prepared by Subhankar Karmakar

6. HARVESTING:

The cutting and gathering of the matured food crop is called harvesting. 

MANUAL HARVESTING:

In harvesting, the crops like wheat or rice are cut close to the ground by hand using a cutting tool called sickle and this is called manual harvesting.

MACHINE HARVESTING:

In large fields, wheat and paddy crops are cut by a motorised machine called harvester.

THRESHING:

After harvesting the crop, the grains are separated from the harvested crops. The process of beating out the grains from the harvested crops plants is called threshing. It can be done manually as well as with the help of a motorised machine called thresher.

WINNOWING: 

The process of threshing brings out grains from the cut and dried crop plants, but this grain is mixed with chaff ( outer inedible covering of grain) and hay. The process of separating grain from chaff and hay with the help of wind is called winnowing.

COMBINE: 

A combine is a large machine which cuts the standing cereal crop in the fields, threshes it, and separates the chaff from grain in one operation.

Lecture-4: CLASS VIII: SCIENCE: CHAPTER -1: WEEDS

CLASS-VIII; SCIENCE

Prepared by Subhankar Karmakar

5) REMOVING THE WEEDS OR WEEDING

Weeds: The unwanted plants or wild plants which grow along with a cultivated crop are called weeds. Like some of the common weeds found in wheat and rice fields are:

(a) Wild oat 

(b) Grass

(c) Amaranthus

(d) Chenopodium

HARMFUL EFFECTS OF WEEDS:

The growth of weeds in the fields is harmful because 

(i) they consume a lot of fertilisers, water, sunlight and space, meant for the crops plants, 

(ii) weeds reduce the crop yield and lower the quality of food grains,

(iii) some weeds are poisonous for human beings and animals,

(iv) some weeds interfere in harvesting.

WEEDING: 

The process of removing weeds from a crop field is called weeding. 

VARIOUS METHODS OF WEEDING:

(a) Removal of weeds by pulling them out with hand.

(b) Removal of weeds by using a trowel ( khurpa)

(c) Destroying the weeds by spraying special chemicals called weedicides.

WEEDICIDES: 

The poisonous chemicals which are used to kill weeds in the fields are called weedicides.  Some of the common weedicides are: 2,4-D, MCPA, Butachlor. 

Lecture 3: CLASS-VIII: SCIENCE: CHAPTER 1: MANURE & FERTILIZER

CLASS VIII   |    SCIENCE    |    CHAPTER 1

      Notes prepared by Subhankar Karmakar

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SCIENCE: CLASS VIII CBSE (CLASS NOTES)

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Lecture 3: 

ADDING MANURE AND FERTILISERS

1. NEED OF MANURE & FERTILISERS

Repeated growing of crops in the same field removes a lot of precious mineral elements, organic matter and other materials from the soil. The deficiency of plant nutrients and organic matter in the soil is made up by adding manures and fertilisers to the soil.

2. MANURES: 

Manure is a natural fertiliser. A manure is a natural substance obtained by the decomposition of animal wastes like cow-dung, human wastes and plant residues, which supplies essential elements and humus to the soil and makes it more fertile.

3. PREPARATION OF MANURES: 

Manures are prepared from animal wastes, human wastes and plant residues by the action of micro- organisms. In order to prepare manure, farmer dump animal wastes and plant wastes in pits at open places and allow it to decompose slowly. The decomposition is carried out by some micro-organisms. The decomposed animal and plant matter is used as organic manure.

4. FUNCTION OF MANURES:

Manures provide a lot of organic matter like humus to the soil. A manure improves the soil texture for better retention of water and aeration. 

5. CHEMICAL FERTILISERS:

A chemical fertiliser is a salt or an organic compound containing the necessary plant nutrients like nitrogen, phosphorus or potassium, to make the soil more fertile. A chemical fertiliser is rich in a particular plant nutrients such as nitrogen, phosphorus or potassium (NPK). Some examples of chemical fertilisers are Urea, Ammonium sulphate, Superphosphate, Potash and NPK.

6. DIFFERENCES BETWEEN MANURES AND FERTILISERS: 

1. A manure is a natural substance obtained by the decomposition of animal wastes like cow dung, human waste and plant residue. 

But a fertilizer is a salt or an organic compound.

2. Manure is not very rich in essential plant nutrients like nitrogen, phosphorus and potassium where as fertilizers are very rich in plant nutrients like nitrogen, phosphorus and potassium.

3. A manure provides a lot of organic matter like humus to the soil but a fertilizer does not provide any humus to the soil.

4. A manure is absorbed slowly by the plants because it is not much soluble in water but being soluble in water if fertilizer is readily absorbed by the plants.

5. Menure can be prepared in the field but fertilizers are prepared in factories.

7. ADVANTAGES OF MANURE:

Organic manure is considered better than Fertilisers because of the following reasons:

1. Manure enhances the water holding capacity of the soil.

2. Manure makes the soil porous due to which the exchange of gases becomes easy.

3. Manure increases the number of useful microbes in the soil.

4. Manure improves the texture of the soil.

8. LEGUMINOUS CROPS:

The pulses, peas, beans, groundnut, gram and clover are called leguminous crops. Leguminous crops have the ability to fix atmospheric nitrogen to form nitrogen compounds. The planting of leguminous crops in a field has the same effect as adding nitrogenous fertiliser in the field.

9. CROP ROTATION:

The practice in which different types of crops like leguminous crops and non-leguminous crops are grown in the same field or soil is called crop rotation. In crop rotation, cereal crops like Wheat, Maize, Paddy and Millet are grown alternately with leguminous crops pulses, peas, beans, groundnut and clover etc. in the same field.

10. ADVANTAGES OF CROP ROTATION:

Rotation of crops has the following advantages:

1. Rotation of crops improves the fertility of the soil and hence increases the production.

2. Rotation of crops saves a lot of nitrogenous fertiliser.

QUESTIONS BANK:

21. Why does soil needs manuring?

22. What are manures? Why it is needed?

23. What are the advantages of manures?

24. What are chemical fertilisers? Give examples.

25. Differentiate between manures and fertilisers.

26. What are leguminous plants? What they are being planted in the field?

27. What are crop rotation? What are their advantages?

Lecture 2: CLASS - VIII: SCIENCE: CROPS -2: IRRIGATION

CLASS VIII   |    SCIENCE    |    CHAPTER 1

      Notes prepared by Subhankar Karmakar

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click to access other class notes

SCIENCE: CLASS VIII CBSE (CLASS NOTES)

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• IRRIGATION

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

• Why is Irrigation Necessary: 

1. Irrigation before ploughing the fields makes the soil soft due to which ploughing of fields becomes easier.

2. Irrigation is necessary to provide moisture for the germination of seeds. This is because seeds do not grow in dry soil.

3. Irrigation is necessary to maintain the moisture of soil for healthy crop growth so as to get good yield.

4. Irrigation is necessary for the absorption of nutrient elements by the plants from the soil.

5. Water supplied to the crops during irrigation protects the crop plants from hot air currents as well as frost.

• Factors Affecting Irrigation Requirements of Crops:

The irrigation requirements of crops depend on three factors:

• 1) Nature of the crop
• 2) Nature of the soil, and 
• 3) Season.

• NATURE OF THE CROP: 

Paddy crop is transplanted in standing water and requires continuous irrigation where as other other crops like wheat, gram, cotton etc. do not require so much water. Hence irrigation depends upon the nature of the crops.

• NATURE OF THE SOIL: 

There are two types of soil on which the crops are grown, (a) Sandy soil and (b) Clayey soil. The crops grown in a Sandy soil need irrigation more frequently where as the frequency of irrigation for the crops grown in a Clayey soil is comparatively less.

• SEASON: 

The frequency of irrigation of the crops is higher in summer season.

• SOURCES OF IRRIGATION:

Crops are supplied water for irrigation from different sources like: Rivers, Canals, Wells, Tube-wells, Dams, Ponds and Lakes.

• TRADITIONAL METHODS OF IRRIGATION:

The various traditional methods of irrigation are:

i) Most (Pulley system),

ii) Chain pump,

iii) Dhekli, and

iv) Rahat ( Lever system)

• MODERN METHODS OF IRRIGATION:

The two main modern methods of irrigation are:

(a) Sprinkler system, and

(b) Drip System.

• 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. It is more useful for the uneven land where sufficient water is not available. It is also useful for Sandy soil.

• DRIP SYSTEM:

In the drip irrigation system, there is a network of narrow pipes 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 wastage of water in this type of Irrigation. Drip system is the best technique for watering fruit plants, trees and gardens.

• ADVANTAGES OF DRIP SYSTEM:

Drip Irrigation system has the following advantages:

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

(b) 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.

Lecture 1: Class VIII: SCIENCE: CROPS AND ITS MANAGEMENT

  Edunes Online Education

Class 8 Science Crops and Its Management
CBSE Notes, Activities & Explanations
Science | Class 8 | CBSE & SEBA Board

Introductions of Crop and its management

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BOARD: CBSE | CLASS: 8 | Science | Chapter 1
📌 Crops and its management

🌾 Class 8 Science – Crop Production and Management (Chapter 1)

💡 Think First:
Food does not come directly from shops. It comes from planned scientific practices carried out on crops.

🌱 What is a Crop?

When the same kind of plants are grown on a large scale in fields to obtain food, it is called a crop.

How to think:
Same plant + large area + food purpose = Crop

Crop Type	Examples
Cereals	Wheat, Paddy, Maize, Millet
Pulses	Gram, Peas, Beans
Oil Seeds	Mustard, Groundnut
Vegetables	Tomato, Cabbage, Spinach
Fruits	Banana, Grapes, Guava, Mango

🧠 Remember: Crops are classified by what we eat from them.

🌦️ Types of Crops

Crops are mainly classified based on the season of growing.

Kharif Crops:
Sown in rainy season (June–September)
Examples: Paddy, Maize, Millet, Soyabean, Groundnut, Cotton

Rabi Crops:
Grown in winter season (October–March)
Examples: Wheat, Gram, Peas, Mustard, Linseed

Think Season → Think Crop
Rain = Kharif 🌧️
Winter = Rabi ❄️

🧠 Kharif drinks rain, Rabi loves cold.

🚜 Agriculture

The practice of growing crops in fields to obtain food is called agriculture.

Think Broadly:
Agriculture = Crop growing + planning + care

🛠️ Basic Practices of Crop Production

The different steps followed by farmers to grow crops are called agricultural practices.

1. Preparation of soil
2. Sowing
3. Adding manure and fertilisers
4. Irrigation
5. Removal of weeds
6. Harvesting
7. Storage of food grains

Think Step-by-Step:
No step skipped → Good yield

🧠 Healthy crop = Right step at right time

🔁 Crop Rotation

Growing different crops in the same field in a planned order to improve soil fertility is called crop rotation.

Think Soil Health:
Same crop again and again → soil weak Different crops → soil strong

🌱 Preparation of Soil

Soil preparation is the foundation of a healthy crop.

1. Ploughing
2. Levelling
3. Manuring

🧠 Good soil = Good crop

① Ploughing

The process of loosening and turning the soil is called ploughing or tilling.

Why plough?
✔ Roots grow easily
✔ Air enters soil
✔ Microbes become active

② Levelling

Levelling is done using a leveller to prevent soil erosion and uneven watering.

Think Balance:
Flat land → equal water → healthy plants

③ Manuring

Adding manure to the soil to increase its fertility is called manuring.

Think Nutrition:
Soil also needs food — manure feeds the soil.

🧠 No nutrition → No production

🔧 Agricultural Implements

Plough:
A traditional agricultural tool made of wood used for ploughing the soil. A wooden plough: The wooden plough consists of a long log of wood which is called plough shaft. There is a handle at one end of the ploughshaft. Below the handle is a strong triangular iron strip called ploughshare. The other end of ploughshaft can be attached to a wooden beam which is fixed at right angles to the ploughshaft.

Think Tool Purpose:
Tool helps farmer do hard work efficiently.

🧠 Final Thought:
Agriculture is a science of care — care for soil, water, seeds, and time.

🔧 (ii) Hoe

💡 Think Tool + Purpose:
Every agricultural tool is designed to solve a specific field problem.

A hoe is an agricultural implement used for:

1. Removing weeds
2. Loosening the soil
3. Turning the soil

Structure → Function:
Long handle → easy movement
Broad iron blade → cuts weeds
Bent shape → loosens soil effectively

It consists of:

1. A long rod made of wood or iron
2. A handle at one end
3. A strong, broad, bent iron plate fixed below the handle (blade)
4. A beam at the other end which is tied to the neck of bullocks

🧠 Hoe = Weed killer + Soil loosener

🚜 (iii) Cultivator

💡 Think Upgrade:
Traditional tools → Slow work Machines → Fast & efficient

A cultivator is a tractor-driven agricultural implement used for:

1. Loosening the soil
2. Turning the soil
3. Ploughing large fields quickly

Why cultivator?
✔ Covers large area at once
✔ Saves time and labour
✔ Improves soil aeration

A cultivator has many ploughshares which dig into the soil simultaneously and turn it.

🧠 Cultivator = Speed + Scale in farming

🌱 2. Sowing

💡 Think Foundation:
A healthy crop begins with correct sowing.

Sowing is the process of scattering or placing seeds into the soil to grow crop plants.

Why is sowing important?
Wrong depth or spacing → weak plants Correct sowing → strong crop

🧠 Sow right today → Harvest more tomorrow

🌾 (i) Selection of Seeds

💡 Think Quality:
The quality of seeds decides the quantity of harvest.

Good quality seeds are:

1. Clean
2. Healthy
3. Free from disease
4. High-yielding

🧠 Bad seed → Bad crop (no matter how good the soil)

🌱 (ii) Methods of Sowing Seeds

There are two main methods of sowing seeds.

(a) Sowing by Hand:
Seeds are scattered manually by farmers.

Limitations:
❌ Uneven distribution
❌ Some seeds too deep or too shallow

(b) Sowing with Seed Drill:
A machine that sows seeds at proper depth and equal distance.

Advantages:
✔ Uniform spacing
✔ Correct depth
✔ Better crop growth

🧠 Seed drill = Smart sowing

🌟 Final Thinking Tip:
Tools prepare the soil, but sowing decides the future crop.

(iii) PRECAUTIONS FOR SOWING SEEDS — How should a farmer THINK before sowing?

Sowing is not just dropping seeds. A farmer must think about depth, distance, and moisture to ensure successful germination.

1. Right Depth: Seeds should be sown at the correct depth suitable for germination.
   👉 Too deep → seed cannot come out 👉 Too shallow → seed dries or is eaten by birds
2. Right Spacing: Seeds should be sown at proper intervals.
   👉 Less space → competition for water & nutrients 👉 Proper space → healthy plant growth
3. Avoid Dry Soil: Seeds should not be sown in dry soil.
   👉 No water → no germination
4. Avoid Waterlogged Soil: Seeds should not be sown in highly wet soil.
   👉 Excess water → lack of oxygen → seed rots

🧠 MEMORY HOOK:
Good sowing = Depth + Distance + Moisture (DDM)

(iv) ADVANTAGES OF SOWING WITH A SEED DRILL — Why is technology better?

A seed drill helps a farmer apply all sowing precautions automatically and accurately.

1. Seeds are sown at correct depth and correct intervals.
   👉 This ensures uniform germination and equal growth
2. Seeds are sown in regular rows.
   👉 Easy irrigation, weeding, and harvesting
3. Seeds get covered with soil.
   👉 Birds cannot see or eat the seeds → prevents loss
4. Tractor-driven seed drill saves time and labour.
   👉 More area covered in less time

🧠 MEMORY HOOK:
Seed Drill = Correct • Covered • Continuous

(v) TRANSPLANTATION — Why don’t farmers sow seeds directly in the field?

Transplantation means shifting young seedlings from a nursery to the main field.

🌱 Example Crops: Paddy (Rice), Tomato, Chilli

Advantages of Transplantation — THINK in terms of SELECTION and GROWTH

1. Selection of Healthy Seedlings:
   👉 Weak or damaged seedlings are rejected 👉 Only strong plants are cultivated
2. Better Root Penetration:
   👉 Roots grow deeper → plant becomes strong
3. Better Shoot Development:
   👉 Strong shoots → more leaves → more food production

🧠 MEMORY HOOK:
Transplantation = Select → Shift → Strengthen

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