There are many good reasons for growers to use some form of soil moisture-sensing technology to monitor conditions and how the water is being used in irrigated crops. First and foremost, it can make good business sense, as irrigation can be fine-tuned and result in savings or improvements in crop yield or quality that can soon claw back the investment in sensor systems. In addition, with climate change and tighter regulation of water abstraction putting pressure on supplies for agriculture, using water resources more wisely and having a record of doing so is becoming much more important.
Essentially, there are two types of soil moisture sensor, water potential sensors such as tensiometers, and granular matrix sensors, and those that give a percentage or relative water content of soil. A tensiometer measures suction pressure at its porous tip, replicating how hard a root has to work to extract water from the soil. These sensors are high-maintenance and only work well in situations where soils stay relatively moist. They also display readings in kilopascals (kPa), which is more difficult to directly relate to water use. Granular matrix sensors pass a current across a porous media such as gypsum, with electric resistance changing proportionally to the amount of water drawn in and out. They are cheap and low-maintenance, but accuracy can be variable.
Sentek, Meter, Labcell and Delta-T are all well-established in the soil moisture sensor market, providing a wide variety of products and services to farmers and horticulturalists. Each of these companies offer different products for farmers and growers to select what suits their needs best, in order to integrate soil moisture sensors into their farm management practices.