Comparing nitrogen budgets in shrimp and rice-shrimp ponds in Vietnam

Duc Dien Luu1,2, Huu Hiep Le2, Michele A. Burford1, Jesmond Sammut3

1 Australian Rivers Institute, Griffith University, 170 Kessels Road, Nathan, Queensland 4111, Australia, www.griffith.edu.au, Email: [email protected]
2 Research Institute for Aquaculture No.2, 116 Nguyen Dinh Chieu Street, District 1, Ho Chi Minh City, Vietnam
3 School of Biological, Earth and Environmental Sciences, University of New South Wales, Kensington 2052, Australia

Abstract

Saline water intrusion has become a severe issue facing the Mekong region of Vietnam, especially in coastal areas. This issue has resulted in farmers diversifying from growing exclusively rice to adopting integrated rice-shrimp culture systems. However, the nitrogen (N) cycling and N use efficiency of these systems remains poorly understood. To address this knowledge gap, we examined nutrient budgets across 12 farms adopting integrated rice-shrimp ponds or intensive grow-out ponds over a one year period. The main N input (95%) in the rice-shrimp ponds came from inlet water, while only 2% of N in outlet water was due to shrimp farming. Shrimp survival rates in mixed rice-shrimp systems were low over the year (4.3 - 5.6%). In contrast, intensive grow-out ponds growing only shrimp on the same farms had significantly higher survival rates (66.4 - 82.3%) when the crop survived through to harvest. In these ponds, formulated feed was the highest input (65% N) with 44% N being in shrimp harvest. These results show that N in the rice-shrimp ponds was used less efficiently than in grow-out ponds and that mechanisms to improve survival rates and production are urgently needed.