Water Content Of Soil – Oven Dry, Infrared, Chemical and Dielectric Method

What Is Water Content of Soil?

The water content of soil is a measure of the amount of water that is held in a given volume of soil. It is often expressed as a percentage, with the total volume of water present in the soil divided by the total volume of the soil. The water content of soil can vary widely depending on the type of soil, climate, and moisture levels.

The water present in soil has a very important role in physicochemical reactions and biological activities in the soil. With changes in the moisture content of the soil, there may be the changes in physical, chemical and biological properties of the soil. Also, this soil water is the main constituent of the growing plants. This water cools the plants by transportation. Also involved in the process of photosynthesis.

Equipment For Moisture Content of Soil Test

The most common equipment used for measuring the moisture content of soil is as follows:

1. Soil moisture meter

This device measures the amount of moisture present in the soil by passing an electrical current through the soil. If the soil is too dry, the meter will read a low number, and if the soil is too wet, the meter will read a high number.

2. Other methods for determining the moisture content of the soil are:

1. Direct Method: These methods are Oven Dry methods, Infrared Methods, etc.
2. Indirect Method: These methods are the Chemical method, Dielectric Method, etc.

Also Read: Shrinkage and Plastic Limit of soil

Moisture Content Test Procedure

1. Oven Dry Method Of Moisture Content

Test procedure for Oven Dry Method of moisture content:

1. Clean the mold properly and take the sample soil from the site or ground.
2. Measure the weight of the soil sample and note it down as W1.
3. Place the soil in the oven at 105°C to 130°C temperature for 1 – 2 hours.
4. After that, place the sample in the desiccator until it cools down.
5. After cooling again measure the weight of the soil sample and note it down as W2.
6. Moisture content is calculated by the initial weight and final weight of the soil sample.
7. The mathematical Formula for moisture content is calculated as

W = [ (W1 – W2) / W1 ] × 100

2. Infrared Method Of Moisture Content

Test procedure for Infrared Method of moisture content:

In this method, the moisture content of the soil sample is measured by the evaporation of water from a soil sample. Equipment named an Infrared meter is used for this method.

• The first step is to balance the instrument by its weight and length of weight chain.
• The infra-red is mounted on the arm and above the pan with changing height.
• The scale shows moisture content in percentage.
• When the balance is zero, the direct value of moisture content is obtained.
• Ground soil samples give instant results as compared to underground soil samples.

3. Chemical Method Of Moisture Content

Test procedure for Chemical Method of moisture content:

• In this method, chemicals are used for removing moisture from a soil sample.
• For calculating the moisture content of the soil sample the soil is placed in a clean mold and then the chemical (calcium carbide) is mixed with the soil.
• The chemical reaction takes place. About 25 – 30 minutes are required for the complete reaction.
• The gas released from the reaction is measured volumetrically or calculated by the weight of the soil measured in the initial and final stages of the reaction.

4. Dielectric Method Of Moisture Content

Test procedure for Dielectric Method of moisture content:

• The dielectric constant is the quantity of material to store the electric current in the electric field.
• In this method, the soil sample is placed in the chamber where the walls of the chamber are made up of plates and connected to the electric field.
• An electric current is passed through the chamber and the capacitance of the soil sample is measured. The value of capacitance of the soil sample varies with the water content present in the soil.
• Therefore, the moisture content is measured by this method on the basis of capacitance, electric current and temperature of the soil grains of the sample.

Water Content Formula Of Soil

The formula for determining the water content of the soil is:

Water Content, W (%) = [(Initial weight of the soil, W1 – Final weight of the soil, W2) / Initial weight of the soil, W1 ] × 100

Mathematically, W (%) = [(W1- W2) / W1 ] × 100

This formula can be used to determine the amount of water present in the soil, expressed as a percentage.

Observation Table

Also Read: Unit Weight of soil