Acid sulfate soils in canegrowing regions of northern New South Wales

Abstract

Acid sulfate subsoils contain iron pyrites (FeS2). Pyrites is stable under anaerobic (saturated) conditions, but when oxidised forms sufuric acid and releases mobile Fe2+ ion. Soil pH can be reduced to as low as 2 and aluminium is released into the soil solution. These conditions can be toxic for plants. Ground water from acid sulfate soils which finds its way to drains and streams, particularly after rainfall following extended dry periods, may kill aquatic life.

Farmer education programs and advice with regard to laser levelling, shallow drains, soil and drain water analysis and treatment of drainage spoil, will reduce the adverse environmental impact of farming acid sulfate soils. Implementation of a rapid tilration test for total sulfidic acidity of soil is proposed; however, research is required to established criteria for critical levels, sampling intensity and sampling depth.