A soil sample weighing 150 g when wet has a dry weight of 120 g. What is the percentage moisture content of the soil on a dry weight basis?

Moisture content on a dry weight basis = [(wet weight − dry weight) / dry weight] × 100. Here, [(150 − 120) / 120] × 100 = [30 / 120] × 100 = 25%. Option A (20%) is a common error from dividing by wet weight instead of dry weight. The dry weight basis is the standard method used in soil science.