Congratulations to Ms. Aye Aye Mon on the successful defense of her masters thesis in August 2000. Mon, a citizen of Burma, worked on PD/A CRSP New Aquaculture Systems/New Species research under the direction of CRSP Co-Principal Investigator Kwei Lin at the Asian Institute of Technology, Bangkok, Thailand.
Use of lotus (Nelumbo nucifera) for nutrient retrieval from pond mud
(abstract of Aye Aye Mons M.S. thesis)
This study was conducted during February to June 2000 to investigate nutrient removal efficiency by lotus (Nelumbo nucifera) from fish pond mud and to evaluate economic return of lotus cultivation in fish pond at the Asian Institute of Technology. This experiment was conducted in twelve compartments (3 x 2 m) in an earthen pond with a randomized complete block design. There were four treatments with three replicates each: no lotus planted (treatment A); lotus planted at 0.5, 1, and 2 rhizomes/m2 (treatments B, C, and D, respectively). There was no nutrient input to the lotus cultivation system, and lotus growth depended solely on the nutrients contained in mud of the fish pond, which was used for intensive fish culture three months prior to the present experiment.
Increased density of planted rhizomes did not result in any significant differences in net and gross production of both total lotus biomass and rhizomes among treatments B, C and D (P>0.05). The net and gross biomass production reached more than 120 t/ha/year in treatment B and C. The highest net and gross rhizome production was achieved in treatment C, reaching 35 and 38 t/ha/year, respectively.
Lotus recovered 1.73-2.5 % of total nitrogen (10.1-14.5 g/m2) and 0.630.99 % of total phosphorus (1.21.6 g/m2) from pond mud in treatments B, C and D. The reduction of both total nitrogen and total phosphorus in pond mud in treatment C was significantly higher than that in the control. Partial budget analysis showed that net return from lotus cultivation in fish pond ranged from 9,234 to 12,599 US$/ha/year, without significant differences among treatments B, C and D.
This study has successfully demonstrated the practicality to cultivate lotus in fish pond for removing nutrients from pond mud and achieve high economic return. Lotus cultivation in fish pond is feasible technically, environmentally and economically.