Defines a gravimetric, reduced pressure drying method to determine the moisture content of fertilizers and liming materials. Does not apply to fertilizers and liming materials which contain calcium nitrate, calcium hydroxide, calcium sulfate containing less than two molecules of water of crystallization for each molecule of calcium sulfate, magnesium sulfate containing one to seven molecules of water of crystallization for each molecule of magnesium sulfate and salts which effloresce readily at ambient temperatures or those which absorb water (desiccants).