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We should contact Decagon to see if odd behavior in metallic soils would be expected...
P.S.(Mar 2014): During teardown, sensor depths were noted as 5, 3, 2 cm for near, far, flr, respectively, not just our usual 5cm at all sites. Since I only sampled 0–6 cm here, we can't look for any depth variation. However, we could expect that far and flr would read drier than near, as did occur.