In eastern Australia, Vettosols are widely utilised for the production of irrigated cotton (Gossypium hirsutum) due to their inherent fertility and large water-holding capacity. However, irrigated

agriculture in eastern Australia is faced with a decline in the availability of good quality irrigation

water sources with low electrolyte concentrations and small Na' contributions.

Consequenrly, alternative water resources that contain larger contributions of Na are becoming

increasingly relevant as potential irrigation sources. It is known that the application of Na rich

waters as irrigation has the potential to increase the Na content of the soil, and that this will affect

the structural condition of Vertosols. However, the extent to which these poor quality water

resources will influence the structural characteristics of different Vertosols is unknown. In addition

to this knowledge gap, there is currently no suitable predictor of dispersive behaviour for this soil

type, particularly where Vertosols are irrigated with different water quality solutions.

The research conducted this study aimed to characterise the impact of different increments of

water quality on the structural stability of different Vertosols. Once this was concluded, the study

looked to assess the impact of irrigation water quality on the structural stability, structural form and

soil water retention properties of intact soil columns. knowledge of the structural stability of the

soils investigated was then used to derive a model describing the impact of water quality on the

structural stability of different cotton producing soils.