The gravimetric method of soil moisture determination Part III An examination of factors influencing soil moisture variability

Abstract The influence of various environmental factors on soil moisture variability in the 0–8 cm horizon is examined. The investigation of the influence of vegetation types revealed at least three tentative variability groups (in order of increasing variability) corresponding to areas of recent cultivation, areas of permanent or ley grass, and predominantly uncultivated moor or heathland areas. The dynamic nature of seasonal variability changes are illustrated and correlations established with the amounts of rainfall and insolation in the week preceding sample collection, and the degree of moisture saturation at the time of sampling. Required sample size was directly related to mean moisture content, or the degree of moisture saturation, and the amount of insolation. It is suggested therefore that a decrease in soil moisture content is associated with a decrease in the variance of sample means, and an increase in moisture content is associated with an increase in variance.