Value of the pF Scale for Water in an Ecological Study of an Insect living in Soil

Abstract

EVANS¹ demonstrated that the energy with which the soil holds water could be correlated with the loss of weight of wireworms; the energy-level was suitably expressed by Schofield's² pF scale. Evans and McL. Guild³ then demonstrated that the rate of production and size of cocoons of earthworms were determined not by the amount of water present in the soil but by the force with which the water was held. Despite these observations the pF scale as a measure of available water for biological processes has scarcely been used in ecological studies of animals that live in soil. Wallace's⁴ paper on the effect of hydrostatic pressure deficiency on motility of larvæ of Heterodera schachtii Schmidt is the only other similar study that I know.