Water content profiles a natural for Campbell systems
Campbell Scientific recently entered a distribution agreement with Sentek Pty, Ltd. of Stepney, South Australia. Sentek's water content profile probes are commonly used in irrigation scheduling and water movement systems. They can be easily integrated into Campbell Scientific data acquisition systems.

Continuous monitoring of soil water content profile produces data to help quantify 1) the onset of crop stress due to over- or under-watering, 2) depth of root zone, and 3) movement of water beyond the root zone. By identifying points of over- and under-watering, the range of optimal water content can be determined, and irrigation frequency can be scheduled to keep water content at optimum. Determining depth of root zone enables scheduling irrigation duration so water moves throughout, but not beyond, the root zone. Measuring water content beyond the root zone helps determine whether nutrients are being leached into ground water.

Most applications of water content profile monitoring require relative data, which is the default mode of Sentek probes. Relative data are produced by an instrument calibrated for a range of soil types. This calibration is used as a default calibration on all soil types. Data cannot be considered as absolute, but reflect soil water changes used as key decision-making criteria in irrigation scheduling. However, the probes can be calibrated to output absolute data.

Specialized tools and techniques allow installation of Sentek probes to minimize soil disturbance. Probe electronics are easily serviced and can be removed during field operations that threaten to damage the probes.

Two Sentek probes are available from Campbell Scientific's US office. EasyAG® is used in cultivated soils of good tilth, commonly found in vegetable production areas. It measures water content at 10 cm, 20 cm, 30 cm, and 50 cm. For installation, we offer a lightweight, inexpensive installation kit for soil textures ranging from light sand to heavy clay. EasyAG® is unsuitable for stony soils where the average stone size is greater than 10 mm.

Sentek's EnviroSMARTTM is recommended for higher accuracy research measurements, measurements deeper than 50 cm, and stony soils (i.e., water use in deep rooted, perennial crops). The Sentek probes can be measured by any of our dataloggers, either through the SDI-12 interface or voltage output.

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