Year 4 (01/07/2001-30/06/2002)

The project scientists have developed methods to remediate and manage shrimp ponds degraded by acid and metal contamination associated with acid sulfate soils and to minimise the effects of soil erosion through pond soil conservation strategies. Hydrogeochemical studies of dyke and pond soils in Australia and Indonesia have described, in detail, the processes that cause pond degradation. The studies found that dyke soils are a major contributor of acid and metals, due to their capacity to generate large amounts of proton and mineral acidity through pyrite oxidation and metal hydrolysis respectively.

Field and laboratory-based studies, as well as hydrogeochemical modelling, were used to calculate more effective lime application rates for commonly used soil types and varying levels of existing acidity and acid producing potential. Liming strategies were developed in combination with pond preparation methods such as fertilisation, drying and flushing. Different types of commercially available lime and modified application strategies were tested for their efficacy, firstly under laboratory conditions and then in the field through a complete production period.

Rapid bioassays and toxicological studies tested the survival of shrimp exposed to leachate from treated soil. Treated pond soil leachate and effluent were monitored and assessed to prevent offsite pollution and toxicity to the farmed shrimp. The study showed that the integration of lime into dyke soil materials was more effective than the standard method of liming the first 10 cm of surface sediments. Where reconstruction of dykes is not possible, the liming and pond preparation strategies developed under the program nevertheless created significant improvements in pond production. The efficacy of lime was increased by using fine-grained lime and when possible applying additional lime in a slurry to avoid loss by wind erosion and to improve seepage into the soil. Slurry mixtures also reduce micro encapsulation of lime granules, improve solubility and reduce loss by wind action.

Survival rates of up to 90% were achieved in formerly abandoned and low-yielding ponds. Improved liming and pond preparation strategies reduced soil pH and associated metal contamination of pond waters, increased survival and growth rates in shrimp and improved the density of beneficial algal blooms. By contrast, ponds treated by standard practices produced lower yields, experienced significant problems with metal contamination, and the depletion of phosphate which is scavenged by metals in the pond soils.

Three alternative farming systems were trialled for severely degraded ponds in Indonesia. Juvenile shrimp production in net enclosures provides a low risk alternative to monoculture. Production periods are limited to 21 days to manage risk associated with fluxes of acid and metals. Juvenile shrimp are a profitable alternative to complete monoculture growout because of the demand for juvenile shrimp by farmers operating ponds unaffected by acid sulfate soils. Net enclosures improved disease management and harvest, and also enabled farmers to move stock during period of poor water quality. Milkfish (Chanos chanos) and seaweed (Gracilaria verrucosa) culture were found to be sustainable alternatives to more risky shrimp monoculture (full growout) due to their higher tolerance to acid and metals.

Simple field techniques to identify acid sulfate soils were developed based on biological, physical and production indicators. A brochure and poster outlining field assessment methods were developed to assist farmers. Improved site selection criteria that address acid sulfate soil assessment were developed to enable farmers, extension officers and consultants to evaluate the suitability of sites for new ponds. GIS and Remote Sensing techniques, soil assessment and geomorphology were used to develop protocols for land capability assessment to map and classify land to assist environmental decision making in aquaculture development programs.

Year 4 (01/07/2001-30/06/2002)

The project scientists have developed methods to remediate and manage shrimp ponds degraded by acid and metal contamination associated with acid sulfate soils and to minimise the effects of soil erosion through pond soil conservation strategies. Hydrogeochemical studies of dyke and pond soils in Australia and Indonesia have described, in detail, the processes that cause pond degradation. The studies found that dyke soils are a major contributor of acid and metals, due to their capacity to generate large amounts of proton and mineral acidity through pyrite oxidation and metal hydrolysis respectively.

Field and laboratory-based studies, as well as hydrogeochemical modelling, were used to calculate more effective lime application rates for commonly used soil types and varying levels of existing acidity and acid producing potential. Liming strategies were developed in combination with pond preparation methods such as fertilisation, drying and flushing. Different types of commercially available lime and modified application strategies were tested for their efficacy, firstly under laboratory conditions and then in the field through a complete production period.

Rapid bioassays and toxicological studies tested the survival of shrimp exposed to leachate from treated soil. Treated pond soil leachate and effluent were monitored and assessed to prevent offsite pollution and toxicity to the farmed shrimp. The study showed that the integration of lime into dyke soil materials was more effective than the standard method of liming the first 10 cm of surface sediments. Where reconstruction of dykes is not possible, the liming and pond preparation strategies developed under the program nevertheless created significant improvements in pond production. The efficacy of lime was increased by using fine-grained lime and when possible applying additional lime in a slurry to avoid loss by wind erosion and to improve seepage into the soil. Slurry mixtures also reduce micro encapsulation of lime granules, improve solubility and reduce loss by wind action.

Survival rates of up to 90% were achieved in formerly abandoned and low-yielding ponds. Improved liming and pond preparation strategies reduced soil pH and associated metal contamination of pond waters, increased survival and growth rates in shrimp and improved the density of beneficial algal blooms. By contrast, ponds treated by standard practices produced lower yields, experienced significant problems with metal contamination, and the depletion of phosphate which is scavenged by metals in the pond soils.

Three alternative farming systems were trialled for severely degraded ponds in Indonesia. Juvenile shrimp production in net enclosures provides a low risk alternative to monoculture. Production periods are limited to 21 days to manage risk associated with fluxes of acid and metals. Juvenile shrimp are a profitable alternative to complete monoculture growout because of the demand for juvenile shrimp by farmers operating ponds unaffected by acid sulfate soils. Net enclosures improved disease management and harvest, and also enabled farmers to move stock during period of poor water quality. Milkfish (Chanos chanos) and seaweed (Gracilaria verrucosa) culture were found to be sustainable alternatives to more risky shrimp monoculture (full growout) due to their higher tolerance to acid and metals.

Simple field techniques to identify acid sulfate soils were developed based on biological, physical and production indicators. A brochure and poster outlining field assessment methods were developed to assist farmers. Improved site selection criteria that address acid sulfate soil assessment were developed to enable farmers, extension officers and consultants to evaluate the suitability of sites for new ponds. GIS and Remote Sensing techniques, soil assessment and geomorphology were used to develop protocols for land capability assessment to map and classify land to assist environmental decision making in aquaculture development programs.

Year 4 (01/07/2001-30/06/2002)

The project scientists have developed methods to remediate and manage shrimp ponds degraded by acid and metal contamination associated with acid sulfate soils and to minimise the effects of soil erosion through pond soil conservation strategies. Hydrogeochemical studies of dyke and pond soils in Australia and Indonesia have described, in detail, the processes that cause pond degradation. The studies found that dyke soils are a major contributor of acid and metals, due to their capacity to generate large amounts of proton and mineral acidity through pyrite oxidation and metal hydrolysis respectively.

Field and laboratory-based studies, as well as hydrogeochemical modelling, were used to calculate more effective lime application rates for commonly used soil types and varying levels of existing acidity and acid producing potential. Liming strategies were developed in combination with pond preparation methods such as fertilisation, drying and flushing. Different types of commercially available lime and modified application strategies were tested for their efficacy, firstly under laboratory conditions and then in the field through a complete production period.

Rapid bioassays and toxicological studies tested the survival of shrimp exposed to leachate from treated soil. Treated pond soil leachate and effluent were monitored and assessed to prevent offsite pollution and toxicity to the farmed shrimp. The study showed that the integration of lime into dyke soil materials was more effective than the standard method of liming the first 10 cm of surface sediments. Where reconstruction of dykes is not possible, the liming and pond preparation strategies developed under the program nevertheless created significant improvements in pond production. The efficacy of lime was increased by using fine-grained lime and when possible applying additional lime in a slurry to avoid loss by wind erosion and to improve seepage into the soil. Slurry mixtures also reduce micro encapsulation of lime granules, improve solubility and reduce loss by wind action.

Survival rates of up to 90% were achieved in formerly abandoned and low-yielding ponds. Improved liming and pond preparation strategies reduced soil pH and associated metal contamination of pond waters, increased survival and growth rates in shrimp and improved the density of beneficial algal blooms. By contrast, ponds treated by standard practices produced lower yields, experienced significant problems with metal contamination, and the depletion of phosphate which is scavenged by metals in the pond soils.

Three alternative farming systems were trialled for severely degraded ponds in Indonesia. Juvenile shrimp production in net enclosures provides a low risk alternative to monoculture. Production periods are limited to 21 days to manage risk associated with fluxes of acid and metals. Juvenile shrimp are a profitable alternative to complete monoculture growout because of the demand for juvenile shrimp by farmers operating ponds unaffected by acid sulfate soils. Net enclosures improved disease management and harvest, and also enabled farmers to move stock during period of poor water quality. Milkfish (Chanos chanos) and seaweed (Gracilaria verrucosa) culture were found to be sustainable alternatives to more risky shrimp monoculture (full growout) due to their higher tolerance to acid and metals.

Simple field techniques to identify acid sulfate soils were developed based on biological, physical and production indicators. A brochure and poster outlining field assessment methods were developed to assist farmers. Improved site selection criteria that address acid sulfate soil assessment were developed to enable farmers, extension officers and consultants to evaluate the suitability of sites for new ponds. GIS and Remote Sensing techniques, soil assessment and geomorphology were used to develop protocols for land capability assessment to map and classify land to assist environmental decision making in aquaculture development programs.

Year 4 (01/07/2001-30/06/2002)

The project scientists have developed methods to remediate and manage shrimp ponds degraded by acid and metal contamination associated with acid sulfate soils and to minimise the effects of soil erosion through pond soil conservation strategies. Hydrogeochemical studies of dyke and pond soils in Australia and Indonesia have described, in detail, the processes that cause pond degradation. The studies found that dyke soils are a major contributor of acid and metals, due to their capacity to generate large amounts of proton and mineral acidity through pyrite oxidation and metal hydrolysis respectively.

Field and laboratory-based studies, as well as hydrogeochemical modelling, were used to calculate more effective lime application rates for commonly used soil types and varying levels of existing acidity and acid producing potential. Liming strategies were developed in combination with pond preparation methods such as fertilisation, drying and flushing. Different types of commercially available lime and modified application strategies were tested for their efficacy, firstly under laboratory conditions and then in the field through a complete production period.

Rapid bioassays and toxicological studies tested the survival of shrimp exposed to leachate from treated soil. Treated pond soil leachate and effluent were monitored and assessed to prevent offsite pollution and toxicity to the farmed shrimp. The study showed that the integration of lime into dyke soil materials was more effective than the standard method of liming the first 10 cm of surface sediments. Where reconstruction of dykes is not possible, the liming and pond preparation strategies developed under the program nevertheless created significant improvements in pond production. The efficacy of lime was increased by using fine-grained lime and when possible applying additional lime in a slurry to avoid loss by wind erosion and to improve seepage into the soil. Slurry mixtures also reduce micro encapsulation of lime granules, improve solubility and reduce loss by wind action.

Survival rates of up to 90% were achieved in formerly abandoned and low-yielding ponds. Improved liming and pond preparation strategies reduced soil pH and associated metal contamination of pond waters, increased survival and growth rates in shrimp and improved the density of beneficial algal blooms. By contrast, ponds treated by standard practices produced lower yields, experienced significant problems with metal contamination, and the depletion of phosphate which is scavenged by metals in the pond soils.

Three alternative farming systems were trialled for severely degraded ponds in Indonesia. Juvenile shrimp production in net enclosures provides a low risk alternative to monoculture. Production periods are limited to 21 days to manage risk associated with fluxes of acid and metals. Juvenile shrimp are a profitable alternative to complete monoculture growout because of the demand for juvenile shrimp by farmers operating ponds unaffected by acid sulfate soils. Net enclosures improved disease management and harvest, and also enabled farmers to move stock during period of poor water quality. Milkfish (Chanos chanos) and seaweed (Gracilaria verrucosa) culture were found to be sustainable alternatives to more risky shrimp monoculture (full growout) due to their higher tolerance to acid and metals.

Simple field techniques to identify acid sulfate soils were developed based on biological, physical and production indicators. A brochure and poster outlining field assessment methods were developed to assist farmers. Improved site selection criteria that address acid sulfate soil assessment were developed to enable farmers, extension officers and consultants to evaluate the suitability of sites for new ponds. GIS and Remote Sensing techniques, soil assessment and geomorphology were used to develop protocols for land capability assessment to map and classify land to assist environmental decision making in aquaculture development programs.