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Sue Philips asked about measuring soil water content within a few cm of the soil surface. I have used the Theta probe (from Delta-T Devices) for this. The probe can be inserted near the vertical (- rod length is 60 mm, diameter is 3 mm and rod spacing is less than 25 mm). They could be inserted at various angles (- including the horizontal position) to give other depths. If there is a temperature response to the analog voltage output, then it would be most important at the soil surface where temperature would vary the most. It is therefore also advisable to measure soil temperature. Usually, we used a 12 V battery to supply continuous power to the sensor. The sensor can be connected directly to a cheap voltmeter - for logging, a CR10X or other datalogger can be used. The sensor has the same problems as other TDR systems - 1. air gaps surrounding the probe created on insertion; 2. compression of the soil on insertion. These two problems can be minimized by very careful insertion - for example, coring out soil using a tool with a diameter slightly less than the rod diameter. This may also minimize the second problem. Other sensors (such as the Campbell Scientific 615 (rod length is 300 mm, diameter is 3.2 mm and rod spacing is 32 mm) which has a much longer rod length) would need to be buried near horizontal to sense such small depths. Michael J Savage, Ph.D. Department of Agronomy University of Natal Pietermaritzburg 3201 South Africa Tele: 27 331 2605514 FAX: 27 331 2605426 E-mail: savage@agron.unp.ac.za