What are the Properties of Soil
Properties of soil
Soil has special properties which determine different soil types. These properties are
- Absorption of water in soil
- Moisture in the soil, and
- Percolation rate of water in soil.
1. Absorption of Water in Soil
The plants that grow in soil require water to grow. If the soil can hold water, the plants will grow well. If the soil does not hold water, the plants would need frequent watering or they would die. The amount of water a particular type of soil can absorb is its water absorption tendency. Higher the absorption of water by soil, higher is its availability to plants.
Activity
Aim: To find out the amount of water absorbed and also water absorbed as a percentage of the weight of soil.
Materials needed: Two conical flasks of equal capacity, two funnels, 20 g sand, 20 g clay, filter paper, and water
Method:
- Place the funnels over the conical flasks as shown.
- Line the funnel with filter paper.
- Place 20 g of sand in one funnel and 20 g of clay in another.
- Pour 500 ml of water in each funnel.
- Observe and note down the amount of water collected in each flask.
- Find out water absorbed by the formula:
A = Initial water – Final water collected A = 500 ml (in this case) – Water collected Percentage of water absorbed = (A/Volume of water taken) x 100
Water absorbed as a percentage of the weight of soil = (A/Weight of soil) x 100
Observation: Clay absorbs more water than sand.
Conclusion: The water absorption capacity of clay is more than sand.
2. Moisture in the Soil
When you take a bit of soil and heat it in a test tube, you will see tiny droplets of water condensing near the mouth of the test tube. Soil contains some amount of water in the form of moisture. We can estimate the moisture content of the soil by the look and feel of it. Soil moisture helps to determine when it needs to be irrigated and how much water it needs.
3. Percolation Rate of Water in Soil
The rate at which water exits the soil is known as its percolation rate. Different soils have different percolation rates. For proper plant growth, it is important to check percolation rate of water in soil. In well-drained soil, water will pass rapidly after it is irrigated. On the other hand, soil with a poor percolation will hold too much water for too long a time. That can be harmful to plants.
Activity
Aim: To find out the percolation rate of water
Materials needed: A watering can, a measuring jar, a trowel, three transparent plastic pipes each approximately 1 foot long/cold drink bottles cut from both sides, water, samples of different kinds of soils kept separately, and a stopwatch
Method:
1. Dig three holes (say, in the garden) and place the three plastic pipes upright in them.
2. Fill three-fourths of each pipe separately with a soil sample.
3. Now fill the remaining one-fourth of each pipe with water and measure the amount of water. Pour the same amount of water in each of the samples.
4. Note the time when you pour water into the soil sample and the time it takes for all the water to be absorbed. Now fill up the table below.
| Soil Sample | Amount of water(in ml) poured (W1) | Time (in min) when water is poured (T1) | Time (in min) when all the water is absorbed/disappears(T2) |
| Sample A | |||
| Sample B | |||
| Sample C |
5. Find out the percolation rate of water using the formula:
Percolation Rate = Amount of water in ml/ Percolation time in min = W1/(T2-T1)
Observation: Which of the three have the highest percolation rate?
Which has the lowest?
Conclusion: The percolation rate of water is inversely proportional to the time taken.
What happens to water when it falls on cemented ground?
Cemented ground is porous to some extent. But the porosity of a cemented floor is very low as compared to soil and, therefore, water absorption is very slow. Most of the water that falls on a cemented floor evaporates or runs off, and only a very small amount seeps through it. Cemented ceilings have to be specially treated to make them waterproof, otherwise waterlogging would result in seepage.