Basic Terminology for Soil Mositure Measurement

For good growth of plants and to provide enough nutrition to plants, it is necessary to maintain moisture content required  by plant. There are sensors to measure the moisture content of ther soil , which can give indication when the plants need watering. Let us understand a few terms of moisture content of soil which can be confusing.  Now, to control the moisture content of soil we need to understand the concept of water holding capacity of the soil. So, we have dedicated this post to explain few concepts of soil moisture content.

The most important thing to understand, while controlling its moisture content is the water holding capacity of the soil. When you pour water in the soil most of the water gets drained out by the force of gravity. The remaining percentage of water in soil which gravity cannot drain out from soil is called water holding capacity of soil. This remaining percentage of water in soil provided necessary water to the plants. So, the more the water holding capacity of plants the better for plants.

You may note here, different types of soil has different water holding capacity. The roots suck the excess remaining water from the soil with pressure determined by capillary actions.When the water retention tension of soil is larger than the capillary pressure of roots, the plant will not be able to drain get he water from soil. This point we define as the wilting point.

So, the amount of water which plant can pull out from soil is termed as plant available water. Now, if you subtract wilting point from water holding capacity from plant you will get the amount of plant available water in soil.  If soil has high water holding capacity, and low wilting point,then then the soil will have higher plant available water which would be good for the plants.

Different types of soil has different holding capacity and different wilting points because composition of soil varies. Sand has low water holding capacity and so water drains out easily, whereas clay soil has high water holding capacity but it also has high wilting point which makes it difficult for plant to pull out water from soil. A proper mixture of clay soil, silt and sand would be required for a soil with high plant available water for plants as an ideal medium for optimal usage of water.

Now, with knowledge of the above terminology, let us take a look at an accurate soil mositure sensor which can provide you a good way to control the soil mositure.

SOIL MOISTURE SENSOR PROBE WITH RTU MODBUS COMMUNICATION

A post regarding using the sensor and calibration can be found on the below link :
Soil Moisture Sensor with RTU MODBUS Communication


Further details can be found on  :

https://en.wikipedia.org/wiki/Field_capacity
https://www.maximumyield.com/definition/1977/water-holding-capacity