THE BUDGET OF NITROGEN IN THE CULTURE OF THE AMAZON RIVER PRAWN AND TAMBAQUI FARMED IN MONOCULTURE AND IN INTEGRATED MULTITROPHIC SYSTEMS
This work aimed to determine the inputs, outputs and accumulation of nitrogen in each of the compartments of the monoculture and polyculture systems with the Amazon River prawn Macrobrachium amazonicum and tambaqui Colossoma macropomum in earthen ponds, using hypereutrophic water. In addition, we tested the hypothesis that the integrated multitrophic aquaculture system (IMTA) is more efficient in using the input of nitrogen than monoculture to produce the two Amazon native species and may be performed in hyper-eutrophic waters.
A completely randomized experiment was designed with four treatments and three replications: MP - monoculture with 30 prawns/m2, MT- monoculture with 1 fish/m2, PF- polyculture (IMTA) with 30 prawns/m2 and 1 fish/m2 free, PH - polyculture (IMTA) with 30 prawns/m2 free and 50 fish/m3 in hapa nets. Samples of water, gas, sediment, feed, and animals stocked and harvested, were all collected throughout the experiment to determine the total nitrogen content and the nitrogen balance.
Results showed that the nitrogen supplied was mainly accumulated inside the ponds as suspended solids and sediment, whereas substantial amount was lost to atmosphere as N2 (Table 1). Only about 1.6% of the nitrogen available was incorporated in the biomass of the target species. Data did not confirm the hypotheses that IMTA is more efficient than monoculture to accumulate nitrogen in the biomass produced. On the other hand, the experiments showed that producing Amazon River prawn and tambaqui in mono or polyculture using hypereutrophic supply waters is technically feasible.