Plants looking healthy and abundantly yielding may suddenly wilt and start declining fast, when there isn't sufficient water available. Even though they may not die fast, their health due to dehydration can be compromised and crop yields. It is situations such as this that sensors can come into play, in determining the water content in the soil, enabling farmers to plan irrigation activities and help the soil yield better crops.
There are two types of soil moisture sensors, volumetric and tensiometric, while the latter measures the potential of moisture in the soil, the volumetric sensors determine the actual quantity of water content in the soil. Tensiometers can determine how tightly the soil in question can hold water.
Tensiometers uses water filled tubes probes through inserting them into the soil up to the level of the roots of the plants. The tubes contain in their bottom end a tip made of ceramic while a gauge is situated on the top of the tube which is above the ground. The moisture tension is registered even as the moisture inside the tube finds a balance with the moisture in the soil outside the tube.
A dry plant requires elevated suction to draw the water from the depths of the soil. This sensor mirrors the suction of water, indicating the dryness of the soil if the reading is higher. Another type of sensor is known as gypsum block. This is also called the resistance to electrical waves.
This is a gypsum block with pores, located on the soil top, with firm contact with the soil. There is a dual electrode system in the block, into these electrodes wires are pushed through, even as the bottom end of the wires enter the soil. As water moves around the block, electrodes measure the electrical resistance that is flung by the water. This resistance is converted into readings by a small meter and the values of tension in the water are determined.