9/2002: Making acidic soils more productive

MEDIA RELEASE

Making acidic soils more productive

A joint Indonesian-Australian research project investigating the links between acidic soils and failed shrimp farming enterprises is delivering benefits to Indonesian farmers and land planners.  Already the results of the project have been used to help ensure environmental problems are avoided in the design of a large-scale irrigation system.

The project, commissioned by the Australian Government through the Australian Centre for International Agricultural Research brought together Indonesian and Australian scientists to solve a puzzling problem, why aquaculture in earthen ponds throughout Sulawesi was failing to produce the expected results.

Shrimp aquaculture in wetlands and mangroves offers a lucrative use for land that is otherwise not profitable.  Smallholders have been attracted to shrimp because it promises a quick and lucrative return.  However, instead of the promised returns, increasing numbers of shrimp were dying, and the problem was beginning to spread into nearby waterways.

Finding the reason behind this situation was the aim of a cooperative research project between Indonesian and Australian scientists.  Using the results of previous ACIAR funded research, the project team found that the presence of acid in the water was the major cause of productivity losses and shrimp mortality.  Research also identified the source of the acid as coming from the soil.

Acid sulfate soils, of which Indonesia has more than 6 million hectares, release acid into waterways when the soil is exposed to oxygen.  By digging ponds for aquaculture the acid was released into the water in the shrimp pond.  This acidic water killed the shrimp and also caused wider environmental problems through washoff from rainfall and tidal flows.

With this understanding of the cause the scientists are now mapping acid sulfate soils to allow farmers to know areas where digging ponds will release acid into the water.  A series of plants that indicate the likely presence of acid sulfate soils have also been identified and this has been passed on to farmers.  This work began with the establishment of a soil and water laboratory at the Research Centre for Coastal Fisheries.

Techniques to fix and manage existing ponds now include modified liming practices.  Combined with improvements in soil and water management, survival rates for shrimp farmed in earthen ponds has reached 60 per cent, a massive improvement on the 5-10 per cent survival rate before the project started. 

Planning and mapping tools and technologies to identify the presence of acid sulfate soils are now being used by provincial governments in Sulawesi to aid decision making on coastal and land developments.  The use of this technology has already seen one large scale irrigation project, that would have seen canals running through acid sulfate soils and releasing acid into the water, moved to avoid the environmental and social damage that would have resulted.