SUGAR CANE AND ACID SULFATE SOILS: TECHNIQUES FOR REDUCTION OF ACID DISCHARGE

Acidic drainage from acid sulfate soils (ASS) is now recognised as a significant problem for best management of coastal and marine resources. Management practices generally recommended for ASS landuse have focussed on avoiding new acidification from pyrite oxidation. While this is important, the main problem, however, is how to best manage and eliminate the export from existing large stores of acidity in ASS landscapes. The model of acid management at McLeods Creek is composed of three phases. First, canegrowers are developing practical techniques of land management that can be adopted by farmers without economic penalty, so as to avoid creation of new acidity and minimise acidity export to drains. Second, the project team is developing and demonstrating sustainable methods of acidity neutralisation in drains, adapted from techniques being developed in the mining industry. Third, the project team has developed and implemented improved floodgate and major drain management. Removal of acidity from caneland drainage has been successful at McLeods Creek because of the integration of landuse and soil and drain management techniques. This has reduced the discharge of acidity from ASS profile stores. The overall goal of the management techniques is to improve the discharge water from about pH 3.5 to above 5.5 and eliminate this as an ASS ‘hot spot’ .