TY - JOUR AU - Maucieri, Carmelo AU - Nicoletto, Carlo AU - Zanin, Giampaolo AU - Birolo, Marco AU - Xiccato, Gerolamo AU - Sambo, Paolo AU - Borin, Maurizio PY - 2020/09/15 Y2 - 2024/03/28 TI - Nitrogen budget in recirculating aquaponic systems with different fish stocking density JF - Italian Journal of Agronomy JA - Ital J Agronomy VL - 15 IS - 3 SE - Original Articles DO - 10.4081/ija.2020.1639 UR - https://www.agronomy.it/agro/article/view/1639 SP - 239-245 AB - <p>As in any agroecosystem, also in aquaponics the nitrogen (N) balance represents an important tool to evaluate sustainability, and to identify factors that can improve N use efficiency (NUE) and reduce N losses. In this respect, fish stocking density has been little investigated, hence this research aimed to evaluate the N balance of a low technology aquaponic (AP) system managed at two fish densities in comparison with a hydroponic system (HP). In the fish tanks common carp at two initial stocking densities were reared (2.5 and 4.6 kg m<sup>–3</sup> in low and high AP, hereafter named APL and APH, respectively) and the vegetated sector was cultivated with a leafy vegetable crop succession (Catalogna chicory, lettuce, Swiss chard). The N balance considered N input as fish feed or fertiliser, and N content in the initial water and the N output as N in the incremented fish biomass, in the harvested vegetables, in the sediments, and in the remaining water. Total N loss was estimated by difference. The total N input and the N loss through gas emission in the atmosphere were much higher in AP than in HP, particularly at high stocking density. The opposite trend was observed for the N input recovered in vegetable aboveground biomass. The N input recovered as fish biomass was slightly higher in APL compared to APH. The better results of APL than APH suggest that in low-tech AP system lower initial fish density should be adopted at the system start up to maximise both production and N recovery.</p><p>&nbsp;</p><p><strong>Highlights</strong> <br>- The higher initial fish density had higher N input, but resulted in a lower N recovered in fish and vegetable biomass, and much higher N loss as gas emissions. <br>- The lower initial fish density combined a lower N input to a higher recovery in fish and vegetable biomass, and a lower N loss as gas emissions. <br>- The lower initial fish density allowed to maximise both production and environmental preservation.</p> ER -