🌱 SCIENCE – CLASS 3
CHAPTER 7: SOIL
Notes BY Prem Sir - Study Kunji
1. SOIL (मिट्टी)
Definition:
Soil is the topmost layer of the Earth's surface in which plants grow.
मिट्टी पृथ्वी की सतह की सबसे ऊपरी परत है, जिसमें पौधे उगते हैं।
Importance of Soil:
Soil helps plants to grow.
Plants get water and minerals from soil through their roots.
Many animals and insects live in soil.
Soil is useful for farmers.
We use soil to make pots and toys.
Example:
🌾 Wheat, rice, vegetables and many other plants grow in soil.
2. FORMATION OF SOIL
मृदा का निर्माण
Definition:
The process by which soil is formed from rocks is called the formation of soil.
चट्टानों के टूटकर मिट्टी बनने की प्रक्रिया को मृदा निर्माण कहते हैं।
Soil formation is a very long and continuous process. It may take thousands of years.
How is soil formed?
Rocks → Heat & Cooling → Cracks → Small Pieces → Weathering → Soil
Explanation:
Long ago, the Earth's surface was covered with rocks.
Due to repeated heating by the Sun and cooling by water and low temperature, rocks develop cracks.
Rocks break into small pieces.
Wind and water carry these pieces to different places.
The pieces become smaller and finer due to wind, water, heat and rubbing.
These small particles mix with humus and other materials to form soil.
3. WEATHERING OF ROCKS
चट्टानों का अपक्षय
Definition:
The breaking of rocks into smaller and finer pieces is called weathering of rocks.
चट्टानों के छोटे और बारीक टुकड़ों में टूटने की प्रक्रिया को चट्टानों का अपक्षय कहते हैं।
Causes:
Wind (हवा)
Water (पानी)
Heat (गर्मी)
Cooling (ठंडक)
Rubbing (घर्षण)
Example:
A large rock slowly breaks into smaller pieces because of heat, water and wind.
4. CONSTITUENTS OF SOIL
मिट्टी के घटक
Definition:
The different materials present in soil are called the constituents of soil.
मिट्टी में पाए जाने वाले विभिन्न पदार्थों को मिट्टी के घटक कहते हैं।
Soil mainly contains:
Humus
Clay
Sand
Gravel and stones
Water
Air
Living organisms
5. HUMUS
ह्यूमस / जैविक पदार्थ
Definition:
The remains of dead plants and animals mixed with soil are called humus.
मृत पौधों और जानवरों के अवशेष जो मिट्टी में मिल जाते हैं, उन्हें ह्यूमस कहते हैं।
Importance:
It makes soil fertile.
It provides nutrients to plants.
It is very useful for crops.
Example:
🍂 Fallen leaves and dead plants slowly decay and become part of humus.
Remember:
More humus → More fertile soil → Better plant growth
6. CLAY
चिकनी मिट्टी
Definition:
Very fine grains of soil are called clay.
मिट्टी के बहुत महीन कणों को चिकनी मिट्टी (Clay) कहते हैं।
Properties:
It is very fine.
It is sticky.
It holds a lot of water.
It contains little air.
It can be easily shaped when wet.
Uses:
Clay is used for making:
Pots 🏺
Toys 🧸
Earthen items
Example:
A potter uses wet clay to make a pot.
7. SAND
रेत
Definition:
Bigger particles of soil are called sand.
मिट्टी के बड़े कणों को रेत कहते हैं।
Properties:
Sand particles are big.
There is a lot of air between sand particles.
Sandy soil does not hold much water.
Example:
🏖️ Sand is commonly found on beaches and in deserts.
8. GRAVEL AND STONES
बजरी और पत्थर
Definition:
Coarse particles of gravel and pieces of stone are also parts of soil.
बजरी के मोटे कण और पत्थरों के टुकड़े भी मिट्टी का हिस्सा होते हैं।
Example:
Small stones can often be seen in garden soil.
9. WATER IN SOIL
मिट्टी में पानी
Definition:
Water present in the spaces between soil particles is called soil water.
मिट्टी के कणों के बीच मौजूद पानी को मिट्टी का जल कहते हैं।
Importance:
It helps plants grow.
Plants take up water through their roots.
Minerals dissolved in water can also be taken up by plants.
Example:
🌱 A plant gets water from moist soil through its roots.
10. AIR IN SOIL
मिट्टी में वायु
Definition:
Air present in the spaces between soil particles is called soil air.
मिट्टी के कणों के बीच खाली स्थानों में मौजूद हवा को मिट्टी की वायु कहते हैं।
Importance:
Plant roots need air.
Many soil animals use this air.
If soil lacks air, plants may eventually die.
Example:
Earthworms and other small animals use the air present between soil particles.
Important Fact:
Soil has many tiny holes or spaces. These spaces may contain air and water.
11. ORGANISMS FOUND IN SOIL
मिट्टी में पाए जाने वाले जीव
Many organisms live in soil, such as:
Earthworms 🪱
Ants
Snails
Insects
Microorganisms
Example:
An earthworm lives inside the soil and makes tunnels.
12. EARTHWORMS – FARMER'S FRIENDS
केंचुए – किसानों के मित्र
Definition:
Earthworms are organisms that live in soil and make tunnels in it.
केंचुए मिट्टी में रहने वाले जीव हैं जो मिट्टी में सुरंग बनाते हैं।
Importance:
They loosen the soil.
Their tunnels allow air to enter the soil.
They help make soil better for plant growth.
Example:
A farmer benefits from earthworms because they help keep the soil loose and airy.
Remember:
Earthworms = Farmer's Friends
13. TYPES OF SOIL
मिट्टी के प्रकार
There are mainly three types of soil discussed in the chapter:
Sandy Soil
Clayey Soil
Loamy Soil
13.1 SANDY SOIL
बलुई मिट्टी
Definition:
Soil containing a large amount of sand is called sandy soil.
जिस मिट्टी में रेत की मात्रा अधिक होती है, उसे बलुई मिट्टी कहते हैं।
Properties:
Found mainly in deserts and seashores.
Has large particles.
Has plenty of air spaces.
Does not hold much water.
Example:
🏜️ Desert soil is generally sandy soil.
Easy Trick:
Sandy = Sand + Less Water
13.2 CLAYEY SOIL
चिकनी मिट्टी
Definition:
Soil made up of very fine clay particles is called clayey soil.
बहुत महीन चिकनी मिट्टी के कणों से बनी मिट्टी को clayey soil कहते हैं।
Properties:
Very fine particles.
Very sticky.
Holds a lot of water.
Contains little air.
Useful for making pots and toys.
Example:
🏺 Potters use clayey soil to make pots.
Easy Trick:
Clayey = Sticky + Holds More Water
13.3 LOAMY SOIL
दोमट मिट्टी
Definition:
Loam is a mixture of sand and clay.
रेत और चिकनी मिट्टी के मिश्रण को दोमट मिट्टी (Loam) कहते हैं।
Properties:
Contains sand and clay.
Has plenty of humus.
Can hold water and air.
Very good for growing crops.
Example:
🌾 Loamy soil is suitable for growing many crops.
Easy Trick:
Loamy = Sand + Clay + Humus = Good for Crops
14. COMPARISON OF SOIL TYPES
| Soil Type | Main Feature | Water | Example/Use |
|---|---|---|---|
| Sandy Soil | Large particles | Holds less water | Desert, seashore |
| Clayey Soil | Very fine and sticky | Holds more water | Pots and toys |
| Loamy Soil | Mixture of sand and clay | Holds water and air | Good for crops |
15. LAYERS OF SOIL
मिट्टी की परतें
Definition:
The different layers found one below another in the soil are called layers of soil.
मिट्टी में एक के नीचे एक पाई जाने वाली अलग-अलग परतों को मिट्टी की परतें कहते हैं।
The chapter describes three main layers:
Topsoil
Subsoil
Solid Rock
15.1 TOPSOIL
ऊपरी मिट्टी
Definition:
The loose top layer of soil containing plant roots and organic matter is called topsoil.
मिट्टी की ढीली ऊपरी परत, जिसमें पौधों की जड़ें और जैविक पदार्थ पाए जाते हैं, topsoil कहलाती है।
Properties:
Loose soil
Contains roots of plants and grass
Contains humus
Suitable for plant growth
Example:
🌱 The soil that we usually see and touch in a garden is mainly topsoil.
15.2 SUBSOIL
उपमृदा
Definition:
The layer of soil below the topsoil, which is more closely packed and contains pieces of rock, is called subsoil.
Topsoil के नीचे की अधिक सघन मिट्टी की परत, जिसमें चट्टानों के टुकड़े होते हैं, subsoil कहलाती है।
Properties:
Harder than topsoil.
More closely packed.
Contains pieces of rock.
Formed from solid rocks.
Example:
If we dig deeper into garden soil, we may find subsoil.
15.3 SOLID ROCK
ठोस चट्टान
Definition:
The very hard rock layer found below the subsoil is called solid rock.
Subsoil के नीचे पाई जाने वाली बहुत कठोर चट्टान की परत को solid rock कहते हैं।
Example:
When we dig very deep into the ground, we may reach hard solid rock.
16. FOSSILS
जीवाश्म
Definition:
The remains of living organisms that died long ago and were preserved deep under layers of rocks are called fossils.
बहुत पहले मर चुके जीवों के अवशेष जो चट्टानों की परतों के नीचे सुरक्षित रह जाते हैं, उन्हें जीवाश्म कहते हैं।
Example:
The preserved remains of an ancient plant or animal found inside rocks are fossils.
17. USES OF SOIL
मिट्टी के उपयोग
Soil is useful in many ways:
1. Growing Plants 🌱
All plants grow in soil.
Example: Wheat, rice, vegetables and fruits grow in soil.
2. Providing Water and Minerals
Soil provides water and minerals needed by plants.
Example: Plant roots absorb water and minerals from soil.
3. Home for Animals 🪱
Many animals live in soil.
Example: Ants, earthworms and insects live in soil.
4. Making Pots 🏺
Clay is used to make pots.
Example: A potter makes earthen pots from clay.
5. Making Toys 🧸
Clay is also used to make toys.
Example: Clay toys can be shaped easily when the clay is wet.
6. Helping Farmers 🌾
Healthy and fertile soil helps farmers grow crops.
Example: Loamy soil is good for growing crops.
18. WHY IS SOIL IMPORTANT FOR PLANTS?
Plants need soil because:
Soil → Water + Minerals + Air + Support → Healthy Plant Growth
Definition:
Soil provides plants with water, minerals and support needed for their growth.
Example:
The roots of a plant grow into the soil and absorb water and minerals.
19. WHY IS HUMUS IMPORTANT?
Answer:
Humus is important because it provides nutrients to plants and makes the soil fertile.
Example:
Dead leaves decay and become humus, which helps plants grow better.
20. WHY IS AIR IMPORTANT IN SOIL?
Answer:
Air in the spaces between soil particles is needed by plant roots and soil animals.
Example:
Earthworms use the air present between soil particles.
⭐ IMPORTANT DEFINITIONS – ONE-LINE REVISION
Soil: The topmost layer of Earth's surface in which plants grow.
Formation of Soil: The process by which soil is formed from rocks.
Weathering: Breaking of rocks into smaller and finer pieces.
Humus: Remains of dead plants and animals mixed with soil.
Clay: Very fine grains of soil.
Sand: Bigger particles of soil.
Sandy Soil: Soil containing a large amount of sand.
Clayey Soil: Soil made up of very fine and sticky clay particles.
Loamy Soil: A mixture of sand and clay, usually rich in humus.
Topsoil: The loose upper layer of soil where many plant roots grow.
Subsoil: The harder layer below topsoil.
Solid Rock: The very hard rock layer below subsoil.
Fossils: Preserved remains of organisms that lived long ago.
Soil Air: Air present in the spaces between soil particles.
Soil Water: Water present in the spaces between soil particles.
🧠 CHAPTER IN ONE FLOW
ROCKS
⬇️
Heat + Water + Wind + Cooling
⬇️
Weathering
⬇️
Small Rock Particles
⬇️
Sand + Clay + Gravel + Humus
⬇️
SOIL
⬇️
Water + Air + Organisms
⬇️
Plant Growth & Life
याद रखने की सबसे आसान लाइन:
Soil = Gravel + Sand + Clay + Humus + Water + Air + Organisms 🌱
तीन Soil Types:
Sandy → Desert/Seashore → Less Water
Clayey → Sticky → More Water → Pots
Loamy → Sand + Clay + Humus → Best for Crops
तीन Soil Layers:
Topsoil → Subsoil → Solid Rock
🌱 Chapter 7 – SOIL
Book से Related Question–Answer
A. Choose the correct option
1. Which of the following live in soil?
a. Earthworms
b. Ants
c. Snails
d. All of these ✅
Answer: d. All of these
2. Soil contains ________.
a. Stones
b. Sand and clay
c. Humus
d. All of these ✅
Answer: d. All of these
3. Which soil is harder than the topsoil?
a. Subsoil
b. Solid rock
c. Both (a) and (b) ✅
d. None of these
Answer: c. Both (a) and (b)
4. Which of the following is the heaviest layer of soil?
a. Gravel ✅
b. Sand
c. Snails
d. Humus
Answer: a. Gravel
B. Fill in the blanks
1. ______ particles are big.
Answer: Sand
2. ______ soil is very sticky and made up of very fine grains.
Answer: Clayey
3. Soil is found in ______ layers.
Answer: three
4. All ______ grow in soil.
Answer: plants
5. ______ is the uppermost layer of the earth.
Answer: Soil
C. True or False
1. Sandy soil holds much water.
Answer: False (F)
2. The heating and cooling of rocks results in the breaking down of rocks into pieces.
Answer: True (T)
3. The water above the layers of clay is very clear.
Answer: False (F)
4. Earthworms harden the soil by digging tunnels in it.
Answer: False (F)
👉 Earthworms loosen the soil.
5. Solid rock is harder than subsoil.
Answer: True (T)
D. Answer the Following Questions
1. What is soil?
Answer:
Soil is the topmost layer of the Earth's surface. It is very important for plants to grow. Plants get water and minerals from the soil through their roots.
2. What are the different types of soil?
Answer:
There are three main types of soil:
Sandy soil
Clayey soil
Loamy soil
Example: Sandy soil is found mainly in deserts and seashores, while loamy soil is good for growing crops.
3. What are the constituents of soil?
Answer:
Soil mainly contains:
Gravel and stones
Sand
Clay
Humus
Water
Air
Living organisms such as earthworms, insects and microorganisms
Example: Garden soil contains sand, clay, humus, water and air.
4. How is soil formed?
Answer:
Soil is formed when rocks break into smaller and finer pieces due to heat, water, wind and cooling. This breaking of rocks is called weathering. These rock particles mix with humus and other materials to form soil.
Example: A large rock slowly breaks into small particles because of heat, water and wind.
5. What are the uses of soil?
Answer:
Soil is useful in many ways:
It helps plants to grow.
It provides plants with water and minerals.
It is home to many animals and insects.
It is useful for farmers.
Clay in soil is used to make pots and toys.
Example: Farmers grow wheat and rice in fertile soil, and potters use clay to make pots.
🧠 Critical Thinking Skills
1. Why do farmers add manure to the soil although all soils contain minerals?
Answer:
Farmers add manure because it adds humus and nutrients to the soil. It makes the soil more fertile and helps plants and crops grow better.
2. A very few crops grow in sandy soil. Why?
Answer:
Very few crops grow well in sandy soil because sandy soil does not hold much water. Water passes quickly through the large spaces between sand particles. Therefore, plants may not get enough water for proper growth.
✏️ Activity Zone – Name the Following
1. I cannot hold water.
Answer: Sandy soil
2. I am used for making pots.
Answer: Clay
3. I am a mixture of sand and clay.
Answer: Loam
4. I am a farmer's friend.
Answer: Earthworm
⭐ Very Important Short Questions
Q1. Which soil holds the least water?
Answer: Sandy soil.
Q2. Which soil is sticky?
Answer: Clayey soil.
Q3. Which soil is best for crops?
Answer: Loamy soil.
Q4. Which soil is a mixture of sand and clay?
Answer: Loam.
Q5. What are the three layers of soil?
Answer: Topsoil, subsoil and solid rock.
Q6. Which layer contains plant roots?
Answer: Topsoil.
Q7. Which layer is harder than topsoil?
Answer: Subsoil.
Q8. Which layer is the hardest?
Answer: Solid rock.
Q9. What is humus?
Answer: The remains of dead plants and animals mixed with soil are called humus.
Q10. Why are earthworms called farmers' friends?
Answer: Earthworms dig tunnels and loosen the soil, allowing air to enter. This helps plants grow well.
Q11. What is weathering?
Answer: The breaking of rocks into smaller and finer pieces is called weathering.
Q12. What are fossils?
Answer: The remains of organisms that died long ago and were preserved deep under layers of rocks are called fossils.
Q13. Where is sandy soil mostly found?
Answer: In deserts and on seashores.
Q14. What is clay used for?
Answer: Clay is used for making pots and toys.
Q15. Why is humus important?
Answer: Humus makes soil fertile and provides nutrients useful for plant growth.
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