How Soil Moisture Detectors Help in Maintaining Farms Smartly?

IoT in Agriculture

Plants gather water and most of their nutrients from the soil. These soil nutrients are absorbed by plants’ roots and transferred through a vascular tissue called “Xylem” to the leaves where photosynthesis occurs. Soil thus supports the entire food cycle by acting as an initial platform for food generation for not only plants but also for other living creatures.

Agriculturists and farmers know the importance of maintaining optimum nutrition and moisture level of the soil to facilitate the growth of crops. Use of fertilizers and manures improves soil’s quality and a robust irrigation system facilitates controlling the water content in it.

Advancements in Internet of Things and sensor technology has given rise to various soil moisture detection systems. By using these devices a farmer can monitor and manage the quality of his soil and choose a crop that is suitable to grow on his fields. There are different mechanisms that these sensors used to determine soil water content. It is therefore important to be familiar with different terminologies related to soil moisture.

Some Keywords Associated with Soil Moisture:

Following are some terminologies that are linked with the measurement of soil moisture:

  • • Soil Water Content: Also called as the soil moisture level, it is the amount of water present in a known amount of soil at a particular time. It is generally expressed as inches of water per foot of soil OR as the % water by weight or volume of soil.
  • • Saturation: Saturation refers to the soil water content when all the pores of soil are filled with water. It is a temporary state as excess water drains out of the soil under the influence of gravity.
  • • Field Capacity: It refers to the soil water content after gravity removes the excess amount of water from its pores. In other terms, it is the amount of water that soil can hold.
  • • Soil Moisture tension: Also referred as the soil matric potential, it is the force with which water clings to the soil. It is generally expressed in bars.
  • • Permanent Wilting Point (PWP): PWP refers to the minimum amount of water in the soil required by a plant to not wilt. If the soil water content is less than the PWP, then the plant cannot regain its turgidity.
  • • Available Water Capacity: It is the amount of water present for the plant growth between PWP and soil’s field capacity. It is also called Plant Available Water (PAW) and is measured as inches of available water per foot of soil.
  • These terminologies are generally used while determining the moisture content of the soil. Different soil moisture detectors use these terminologies to indicate the quantity of moisture present in it. Soil moisture sensor working, generally depends on the mechanisms used by the sensors.

Different Types of Soil Moisture Sensors:

1) Reflectometers:

Soil moisture sensors using reflectometry determine the water content by measuring the change in a specific parameter once it is reflected by the soil. In a reflectometer, there are generally two or three metallic rods that are deeply inserted into the soil. A wave of known parameter is passed through these rods. The sensor catches the reflected wave and amount of moisture present in the soil is determined based on the changes in the parameters.

Based on the parameters used by the reflectometer, they are classified into three different types:

  • • Time Domain Reflectometer (TDR): parameters are speed and strength of the electromagnetic wave
  • • Frequency Domain Reflectometer (FDR): parameter is the frequency of the wave
  • • Amplitude Domain Reflectometer (ADR): parameters are dielectric constant and soil electrical conductivity of an impedance signal.

2) Time Domain Transmission (TDT):

A time-domain transmissometer is similar to a TDR, however, it is made up of a complete loop where both ends are connected with an electric source. TDT measures the time taken by the pulse to propagate through the complete loop once it is buried deep into the soil. The time taken by the pulse to propagate will be more for moist soil than dry soil. By considering the time taken by the pulse, the amount of moisture present in the soil is estimated.

3) Tensiometers:

A tensiometer takes use of soil moisture tension to determine the moisture content in the soil. It consists of a glass tube that is filled with water. The end of the tube is fitted with a porous tip that is inserted deep into the soil. The soil extracts the water from the tube due to soil moisture tension as soon as its moisture decreases. This creates a vacuum in the tube that reflects the change in the soil water content.

4) Granular Matrix Sensors:

This sensor measures electrical resistance to determine the moisture level in the soil. It consists of electrodes that are enclosed in a granular matrix made up of quartz. This apparatus is confined in a gypsum solution filled in a metal case. A small electric charge is passed through the electrodes and the electrical resistance through them is measured. In case, the moisture in the soil decreases, the water from the sensor will be extracted by the soil and thus the resistance will increase. This change in the resistance level is then used to estimate the soil water content.

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An IoT Powered Soil Moisture Management System:

Soil moisture is an important characteristic that facilitates the growth of plants. It acts as a solvent for different nutrients present in the soil and itself acts as a primary ingredient for photosynthesis. It regulates the soil temperature that further ensures the blooming of new plants.

Measuring the soil water content is therefore important to maximize the crop yield and ensuring its quality. Soil moisture sensors working on different mechanisms have emerged that are assisting farmers to remain updated about the quality of their farms’ soil.

IoT powered soil moisture detection system is one of the many applications of agricultural IoT. The data gathered through moisture sensors is transmitted via a gateway to a centralized platform that acts as a command center for a farmer. By using the data on this platform, he can monitor and manage different farming operations remotely and can ensure the quality and health of his crops.

Hardware Used:-

Intellia INT G01- Soil Moisture Sensor

Intellia INT G01- Soil Moisture Sensor (Transmitter) is a high precision, high sensitivity soil moisture measuring instrument. This product is a metal shell, high compressive strength, good sealing performance; the use of electromagnetic pulse principle to measure the apparent dielectric constant of the soil.

Quick Specifications
Model No INT G01
Monitoring principle FDR
Structure 4-pintype
Output Signal 4-20mA
PowerSupply DC12-24V
Response time <1s