Calcium Carbide Gas Pressure Moisture Testers comply with ASTM D4944, AASHTO T217 and Florida FM 5-507 methods. The economical, American-Made Gilson Aqua Check and the Speedy Moisture Tester both provide efficient and accurate moisture determinations in the field. A moist soil sample is agitated together with calcium carbide reagent in the test cell. Gas generated by the reaction pressurizes a dial gauge for direct percent moisture readings. The readings could be strategized and associated with readings from laboratory oven-dried moistures for increased accuracy. The Kelway Soil Acidity/Moisture Meter is a probe inserted in the soil that reads differences in electrical potential to estimate pH and relative moisture values.