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Hello everybody ! We are manufacturer of an innovative irrigation control system based on soil moisture content (see our web site for more info: http://www.SmartRain.com). Our sensor also measures soil conductivity and we wish to correlate it with soil salinity if possible. I wander if anyone could help us with the following problem: To our knowledge, the easiest and standard way to measure soil salinity is to measure its electrical conductivity. Unfortunately, measuring electrical conductivity is not always obvious. Using direct current (DC) will polarize the electrodes of the probe used and plate them. Using a too low frequency alternative current (AC) is better but will do the same with time. On the other hand, using a too high frequency current will create dielectric losses and increase the conductivity over its normal ionic level. Also, we have experimentally observed that the conductivity level is actually very dependant on frequency. Therefore, what is the optimal frequency if any ? The second part of the problem arises from the fact that conductivity is also very much dependant on soil moisture. Some manufacturers even use conductivity to measure soil moisture !!! Therefore, what is the ideal soil moisture level at which conductivity must be measured in order to correlate with soil salinity ? We heard that laboratories were using field capacity ? Also, do you have any equations or empirical relationships relating soil salinity and soil conductivity at a certain frequency ? Thank You in advance for your help. Romain Gagnon, Eng Smart Rain Corporation inc 1505, Place de l'Hotel de Ville, suite 102 St-Bruno, Quebec, Canada --- J3V-5Y6 E-mail: Info@SmartRain.com Phone: 1-514-441-4289 FAX: 1-514-441-2147 WEB: http://www.SmartRain.com