Page 91 - Science Class 07

Soil : The soft upper layer of the earth’s crust
Humus : Organic matter present in upper layer of soil
Weathering : Natural process through which rocks break down into small particles

Soil profile : Sample taken from the surface down through the soil
Texture of soil : Shape and size of the soil particles
Soil erosion : Taking away top layer of soil by fast moving air or water

Percolation : The process through which water moves downwards into the soil through
small passage present in the soil

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i Soil is capable of supporting plant life and is vital to life on the earth.
i The gaps between the soil particles contain air and water. Air and water are important
constituents of soil.
i Soil formation is a very slow process.
i Weathering includes penetration of plants roots in rocks, freezing of water in the cracks
present in rocks due to low temperature.

i Each soil profile is divided into a series of layers called horizons.
i O-horizon is the topmost layer while bed rock is the lower most layer of the soil.

i In hilly areas, farming is done by cutting steps on the slopes of the hills.
i Important types of soil found in India are alluvial soil, black soil, red soil, laterite soil, desert
soil and mountain soil.

i Due to soil erosion, top fertile soil is lost which results in infertility of soil.

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A. Tick (3) the correct op on.
1. Which of the following horizons contains largest quan ty of minerals?
(a) O-horizon (b) A-horizon
(c) B-horizon (d) C-horizon
2. Which type of soil has par cles less than 0.2 mm in diameter?

(a) Sandy soil (b) Clayey soil
(c) Loamy soil (d) None of these
3. Which of the following soils is good for growing co on?
(a) Alluvial soil (b) Black soil

(c) Mountain soil (d) Red soil

Science-7 91