Seasonal sodium flux in a woodlot soil irrigated with secondary treated effluent

Previous research has shown woodlot soils receiving secondary treated effluent undergo an increase in Exchangeable Sodium Percentage (ESP) over time. Increased soil ESP influences micro-aggregate/soil pore stability and, particularly when subject to irrigation waters of specific low electrolyte concentrations, results in decreased soil permeability and a subsequent need to reduce application rates. The hypothesis is that sodium flux will directly alter hydraulic conductivity over time and if the range of seasonal sodium flux is too great, potentially dispersive conditions are more likely to occur. This study aimed to quantify seasonal sodium dynamics (flux) in a woodlot soil receiving secondary treated effluent in order to predict the effect variations in soil ESP and effluent/rainfall electrolyte concentration have on relative soil permeability. The principal outcome finds the seasonal sodium flux is greater than could have been previously recognized in other studies and that proven theories can be used to conceptualise a continuum for micro-aggregate/soil pore stability in the soil profile. This in turn can be used as a management tool for assessing relative permeability for soils receiving secondary treated effluent. The implication is that the prediction of potentially dispersive irrigation/rainfall events can be employed to direct and maximize effluent irrigation scheduling.