As bio-integrated systems that link both plants and fish culture, inside aquaponics systems, the prosesses of ammonia-oxidizing and nitrification in nitrite and nitrate are essential for growth and development of both fish and plants culture biomass. Plants with nearly the same nutritional requirements during their life cycle, like spinach in this case, are recomended to be grown under aquaponic condition. Although nitrate concentration up to 200-250mg/l are reported to be acceptable for fish growth. The toxic effect of long term exposure to high nitrate levels on fish and plants cultured biomass were highlighted. The main goal is to compare the nitrate level of spinach , grown in aquaponic system, under three plant densities (V1-59 plants/m2; V2-48 plants/m2 and V3-39plants/m2). The second objective is to compare the results obtained, in term of nitrate content, for spinach grown in the integrated rainbow trout-spinach aquaponic system with those of marketable spinach , grown under conventional condition, in the field. This design consists i a recirculating aquaculture system with 12 growing units, mechanical and biological water treatment units and four aquaponic units. Fish were fed with two types of feed with 41% and 50% protein using 3 different feeding regimes. The result show a higher nitrate level on spinach grown in aquaponic system, compared to the one derived from field culture. Differences were observed also among the three variants grown in aquaponic system, compared to the one derived from field culture. Differences were observed also among the three variants grown in aquaponic conditions, under different plant densities. As a conclusion, it can be said that considering the nitrate level, spinach grown in aquaponic system is marketable.
#The Annals of the University Dunarea de Jos of Galati
Fascicle VI -Food Technology (2013), 37(2), 47-58