The determination of the volume and air space of soil clods

A method is described for determining the field volume and the air space of a clod of any shape by filling its pores with a hydrocarbon oil, such as paraffin or tetralin, and determining its weight in the oil and in air before and after impregnation. The method appears to work well for clods of any moisture content.This method is shown to give values of these volumes entirely comparable with those given by the other accurate methods described in the literature. Its accuracy for clods of Rothamsted soil, weighing between 20 and 500 g., was probably at least 1 part per thousand, i.e. 0-1%.The method has been applied to the determination of the available water held by a soil and has been used to illustrate the effect of long-continued applications of farmyard manure to a soil in increasing the amount of available water it can hold.