Meaning of soil
The upper layer of the earth in which plants grow is known as soil.
Importance of soil
Soil plays a vital role in each and everyone’s life and also mainly it plays a vital role in the earth’s ecosystem. Without soil humans life would be very difficult. Soil filters the rainwater and helps in regulating the discharge of excess rainwater from preventing flooding. Soil is having the capability of storing excess water or large amounts of organic carbon.
Benefits of soil that provide
There are many benefits of soil
c) Aeration and structure
d) Soil improvement
So now we are going to discuss about soil chapter
Soil provides anchorages that supplies water and nutrients. Soil is very important for agriculture which provides food, shelter, clothing. Polythene and plastic bags pollute the soil and kill the organisms. Waste products and chemicals should be treated. Use of pesticides should be reduced. Soil profile has distinct layers. Humus is nothing but in the soil the rotting dead matter which is there is known as humus.
- Particle size-clay
- Weathering-breaking down of the rocks by wind, water and climate
- Nature of the soil depends on the rocks from which it is formed and the type of vegetation which it grows.
Vertical section-soil profile
Layers are called horizons-different colour, texture, depth and chemical composition. Layers are seen on the side of the roads while they are digging them.
It is dark in colour with humus, it makes the soil fertile, soft etc and even it can retain the water.
A horizon: It provides shelter for living organisms;roots are embedded in topsoil.
B horizon: It is with less humus, more minerals, harder, compact and middle layer.
C horizon: It is a small lump with cracks and crevices.
Bedrock: It is lowermost and hard to dig.
Types of soil
Soil is a mixture of rock particles and humus. Bacteria, plant roots and earthworms are the most important part of the soil.
- Sandy soil : It has bigger particles;larger spacing light and dry.
- Clayey soil: It has finer particles; lesser air, heavier and it can hold more water.
- Loamy soil: It is the best topsoil for plant growth-mix of sand, clay and silt occurs as deposits in river beds and size between sand and clay. It has humus and right water holding capacity.
Water holding capacity is decided by size of the soil particles and in between spaces.
Properties of soil: Percolation rate of water-water absorbs on kutcha road and not on pucca road.
Percolation rate(ml/minute)=Amount of water(ml)/percolation time(minute)
- In sandy soil the percolation rate will be high
- In clayey soil the percolation rate will be least
Moisture in soil
Amount of water in soil. On heating water gets evaporated, moves up and condenses the cooler inner wall. On hot summer days vapor reflects sunlight and air above soil seems to shimmer. Soils contain water on heating , the water of the soils gets evaporated and soil becomes loose.
Absorption of water by soil: Water retained in soil is the amount of water in cylinder minus. Grams and kilograms are the units of mass.
Soil and crops
Soil is affected by winds, rainfalls, temperature, light and humidity and this affects soil profile and structure. Climatic factors and soil components determine vegetation and crops.
- Clayey and loamy are good for cereals like wheat and gram.
- Paddy-Soil rich in clay and organic matter are good.
- Lentils: Loamy soil which drains water easily.
- Cotton: Sandy loam and loamy soil-hold plenty of air.
- Wheat- Fine clayey soil-rich in humus and fertile.
Clayey for making pots
Burnt horse dung helps open up in the porse in the soil. So that water could percolate out of the matkas, evaporate and cool.
- Removal of topsoil(due to absence of plants in topsoil)-prevent deforestation and increase in green areas.
- North india rivers- bring alluvial soil- fertile and support half of the population.
- Water-loggedsoils-roots are deprived of oxygen and harmful for plants.
- Dense forest has less soil erosion due to huge tree canopy which prevents rainwater from falling on ground.
Benefits of soil digging
The benefits of soil digging are for enabling easy root growth, for easier percolation of water, for removing the weeds. Bore wells are deeper in urban areas than in rural areas due to excessive depletion in urban areas.
This is some of the information about the soil chapter which is a very important chapter in class 7. It helps everyone in many ways like competitive exams etc. It is most important from which we can gain a lot of knowledge.