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Luke, You should consider the tensionic device with which you can simultaneously measure the water potential and extract the soil solution. It is a sort of double use tensiometer. I would suggest using at least three tensionics per measuring site : one in the root zone and 2 at the bottom of the root zone. The water potentials will give you the water flow direction which you can use to explain the increases or decreses in the soil solution composition (at least for soluble elements). Then if you have more money and would like to calculate the amount of nutrients leached, you might need to use a water content measuring probe. Of course, you will have to supose that a measurement takinbg at a certain depth is valid for a certain thickness of soil (10 cm for example) and people might not agree with that but it is an approach. A tensionic is about 70 US$. You need a pressure sensor to measure the water potential (hydraulic head) and a simple seringe to extract the soil solution. See on the tensionic device a paper written by Dr. Moutonnet : Moutonnet P, Pagenel JF, Fardeau JC, 1993. Simultaneous field measurement of nitrate-nitrogen and matric pressure head. Soil Science Society of America Journal. 57:1458-1462. Good luck. Henriette ---------------------------------------------------- Henriette CUNY SDEC France - Scientific Instrumentation - Z.I de la Gare - 37310 Reignac/Indre France (Europe). Tel : 33 2 47 94 10 00 / Fax : 33 2 47 94 17 13 Check our WEB site : http://www.sdec-france.com and have a nice day measuring water potentials in the fields _______________________________________________