Brief Introduction :

Soil moisture is an important parameter in agriculture and horticulture. A moderate amount of water in the soil is necessary for the proper growth of plants. Too much or not enough water can lead to various plant diseases and reduced crop yields. So farmers and gardeners need to monitor soil moisture levels regularly. In this article, we will discuss soil moisture sensors and their importance in modern agricultural practices. We will also look at different types of soil moisture sensors and their applications.

What is a soil moisture sensor?

A soil moisture sensor is an electronic device that measures the amount of water in soil. The sensor detects changes in the soil’s dielectric constant, which is related to the soil’s water content. A typical soil moisture sensor consists of two electrodes placed in the soil. As the current is passed between the electrodes, the capacitance of the soil is measured and the moisture content is estimated from the measured capacitance.

Why is soil moisture important?

Soil moisture is critical to plant growth and its importance cannot be overemphasized. Plants absorb water through their roots, which is necessary for photosynthesis, the process by which plants produce food. If there is not enough water, the growth of plants will be stunted and the leaves will die. On the other hand, excessive water can cause root rot, which can lead to plant death. Therefore, maintaining a proper balance of soil water is essential for plant health and growth.

Soil moisture sensor Type :

There are different types of soil moisture sensors available, each with its advantages and disadvantages. Let’s take a look at some of the most popular soil moisture sensors:

Tensiometer:

The tensiometer is one of the oldest soil moisture sensors. They consist of a hollow ceramic cup filled with water and a porous ceramic tip at the bottom of the cup. The ceramic head is inserted into the soil and the cup is connected to the vacuum gauge. As the soil dries, water is pulled out of the cup, creating a vacuum. A vacuum gauge measures the pressure inside the cup, which is related to the water content of the soil.

Tensiometers are relatively inexpensive and easy to use. However, they require constant maintenance and readings are subject to temperature changes.

Time domain reflectometer (TDR):

The TDR sensor uses an electromagnetic pulse to measure the soil’s dielectric constant, which is related to the soil’s water content. The sensor sends a pulse of electromagnetic energy into the soil and measures how long it takes for the pulse to bounce back to the sensor. The reflection time is related to soil permittivity, which in turn is related to soil water content.

TDR sensors are highly accurate and reliable, but they can be expensive and require calibration.

Capacitance sensor:

The working principle of capacitance sensor is capacitance sensing. They consist of two electrodes placed in the soil, and the water content is estimated based on the capacitance of the soil. When the soil is dry, its dielectric constant is low and so is the capacitance between the electrodes. When the soil is wet, its dielectric constant increases and so does the capacitance between the electrodes.

Capacitive sensors are relatively cheap and easy to use. However, they are affected by soil temperature and salinity.

Resistance sensor:

Resistance sensors work by measuring the resistance of soil. They consist of two metal electrodes placed in the soil, and the water content is estimated based on the resistance of the soil. When the soil is dry, its resistance is high and when it is wet, its resistance is low.

Resistance sensors are relatively cheap and easy to use. However, they are affected by soil temperature and salinity.