Abstract: Farming rice and shrimp in an integrated pond system is practiced widely in the Mekong Delta where dry season soil and water salinity is too high to continue with rice monoculture. These integrated systems involve farming rice in the wet season when soil and water salinity is normally negligible, and shrimp in the dry season when soil and water salinities exceed the tolerance of rice. In recent decades, these systems have been subjected to rising salinity due to climate variability and reduced freshwater flows into the Mekong Delta from upstream river regulation for dams and abstraction of water for other land uses. Consequently, wet season salinity is increasing and creating sub-optimal conditions for rice; dry season salinity is also becoming sub-optimal for shrimp at some locations due to hypersalinity.-Nevertheless, these rice-shrimp systems, when risks are managed and location conditions are suitable, provide an opportunity for farmers to maintain production throughout the year. This project was initiated at the request of the Ministry of Agriculture and Rural Development (MARD) to 1) test the farming system for scaling out; 2) identify risk factors for rice and shrimp production; 3) better understand the benefit of growing rice and shrimp together; and 4) create a basis for developing better management practices. Initially there was a focus on scientifically validating the efficiency of these systems; however, severe drought conditions caused recurrent rice crop losses and impacted on the research at Hoa My Commune in Ca Mau where farmers faced the challenges of severe salinity and acid sulfate soils. This led to more in-depth research on the risk factors for rice and shrimp production. -A review of the project recommended that the project should be extended to include research activities at study sites that were less impacted by severe drought. The project extension enabled the team to conduct field trials on system processes, farming risk factors and testing better management practices. Tan Bang Commune was selected as a second site. Site characterisation and risk factors for rice and shrimp production where evaluated along with data collection at Hoa My Commune for comparative purposes. Based on the findings of the risk factor studies, and the outputs of a scientific and expert (farmer) Bayesian Belief Network (BBN), a series of salt-tolerant rice trials were conducted, better farming practices were tested for rice and to a lesser extent shrimp, and shrimp health was evaluated and linked to farm conditions to create a knowledge platform for future research. The trials identified suitable salt-tolerant rice varieties, demonstrated that sludge from shrimp farming could be used to replace fertiliser for the rice crop, and rice platform conditions could be improved by tilling, washing and leaching of the residual salt and modifying the rice growing platform. --- The project also made recommendations on the timing of sowing to address salinity issues that affect the early stages of rice growth. These practices reduce the need for fertiliser, have improved rice yields, and increased the profitability of rice-shrimp farming system. The study found that natural food production is low for shrimp due to water quality conditions that do not enable the conversion of nitrogen to natural food. Shrimp are also stressed by low dissolved oxygen concentrations and, periodically, by salinity and water temperatures outside their optimal range for growth and to maintain health. Further research is needed to test better management practices for shrimp nutrition and methods to increase dissolved oxygen concentrations and temperature conditions. Pilot trials demonstrated that shrimp yields could be improved e.g. supplementary feed can increase the value of the shrimp crop by USD 1500 annually.
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