- 1. see puff3. a unit formerly used in agricultural science to measure "soil suction" or soil moisture tension. Soil moisture tension is the pressure that must be applied to the moisture in the soil to bring it to hydraulic equilibrium with an external pool of water. This was measured in pF units as the logarithm of the pressure in centimeters of water. Currently measurements are usually made directly in kilopascals (kPa).
Dictionary of units of measurement. 2015.