 # 7th Class Chapter No 9 - SOIL in Science for CBSE NCERT

Percolation rate of water in soil

• Percolation is the property of absorption of water by soil.
• If we pour a bottle of water on the floor and another bottle of water in the soil, the water on the floor will flow down but water in the soil will be absorbed.
• The percolation rate is the amount of water absorbed by any soil at any given time.
• Formula for calculating percolation rate is,

Percolation rate (ml/min) = amount of water (ml) / percolation time (min).

• For example, If 200 ml of water is percolated through the soil sample in 40 min. Calculate the rate of percolation.

Solution – Rate of percolation is = amount of water (ml)/ percolation time (min)

= 200 ml/ 40 min

= 5 ml/ min

Ans-  The rate of percolation is 5 ml/ min.

Moisture in soil

• Moisture is the amount of water present in soil.
• During summer, the water content in the soil evaporates and moves up which reflect the sunlight, thus the air above soil seems to shimmer.

Absorption of water by soil

• Different soil samples absorb water in different extent.
• The absorption of water by different soil can be find out by taking 50g of different soil samples.
• Pour the soil in different funnels placed in different beakers and pour water in the soil with the help of measuring cylinders.
• Continue pouring until it starts dripping.
• Now, check the amount of water left in the measuring cylinder and subtract it from the initial amount which was taken.
• The resulted amount of water is retained by the soil.
• Formula to calculate percentage of water absorbed is
• Percentage of water absorbed = {(U-V)/50} X 100,        50g is the amount of water absorbed.

U is the initial volume of

V is the final volume of water (ml)

Posted in 7th on February 13 2019 at 03:29 PM

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