Remote Soil Moisture Monitoring

The purpose of a soil moisture monitoring system is to deploy probes or sensors to detect soil moisture conditions which are critical to optimal crop production. Monitoring soil moisture status allows the farmer or consultant to detect plant stress before the plant displays obvious signs of stress. Avoiding this unneeded stress can provide more optimal growth, increase yields, and enhance the overall quality of the crop. RSMM may also help the grower avoid overwatering, thereby decreasing potential water logging of the roots, root diseases, unnecessary water use, and nutrient leaching from the root zone. Soil moisture monitoring probes and sensors are available from a number of vendors and come in many forms, shapes, and sizes. Some probes are directly installed into the soil near the crop root zone while others measure canopy temperature from above to indirectly quantify soil moisture status. Each probe or sensor differs in the sensing method for measuring the soil moisture. The soil water tension sensor uses the electrical conductivity between two electrodes embedded in a ceramic or gypsum material. The electrical resistance between the two electrodes increases as water is drawn from the material. This sensor is installed in the soil and responds to changing soil moisture conditions. The sensor can be read with a handheld meter or through various dataloggers and/or remote telemetry. Another sensor option is a capacitance probe. This probe consists of a number of sensors (made up of pairs of circular rings) mounted on a vertical column and is then protected by a waterproof outer tube. Capacitance soil moisture sensors use electronics to measure the dielectric constant of the surrounding material (usually the soil) which happens to be related to moisture content. Soil moisture stress can also be measured indirectly using a canopy temperature sensor. One vendor determines temperature using an infrared thermometer. Research has shown that crop canopy temperature can be related to crop stress levels caused by lack of soil moisture. If the temperature of a crop reaches an above-optimal temperature for an elongated period of time, the individual plants transpire water less efficiently which can be detrimental to the overall yield. The majority of soil moisture sensing technology on the market allows the farmer to use the Internet to securely log in and access real-time data on which to base an irrigation decision. Sensors within the probes are often placed at multiple depths (8 , 16, and 24 inches, for example) below the soil surface so the farmer or consultant can better interpret crop water needs or plant stresses.