Evaluation of lettuce cultivation in an aquaponic system, with and without bioflocs, compared to a hydroponic system, in a greenhouse in southern Brazil

AbstractA recirculation system was set up to evaluate lettuce production (floating) in aquaponics (Aqua) and aquaponics with bioflocs (AquaFloc) in comparison to hydroponics (Hydro), in triplicate, for 45 days. Juvenile tambacu into the aquaponics tanks were fed with a commercial feed. Water quality was monitored and vegetable growth was evaluated. Head diameter, height, fresh matter, dry matter, number of leaves, and chlorophyll a+b concentration were higher (P<0.05) in “Hydro” than “AquaFloc”, even when the “AquaFloc” reached 60 days. The “AquaFloc” system presented 62% of fish survival, but presented lower (P<0.05) concentrations of ammonia and nitrite compared to “Hydro” and absence of nitrate. Electrical conductivity and concentration of total solids dissolved in water were lower (P<0.05) in “AquaFloc” than in “Hydro”, while pH was higher (P<0.05) in “AquaFloc” in comparison with “Hydro”, resulting in less availability of nutrients for plant growth. The “Aqua” system did not show lettuce growth and presented a complete fish mortality. The fish-vegetable ratio used did not meet the nutritional demand of the lettuces. New studies must be carried out with an appropriate fish-vegetable ratio that can provide sufficient nutrients to plants in aquaponics, with control of the system's pH.

摘要：本研究搭建循环养殖系统，以水培（hydroponics, Hydro）为对照，分别评估鱼菜共生（aquaponics, Aqua）与添加生物絮团（bioflocs）的鱼菜共生（aquaponics with bioflocs, AquaFloc）体系内浮栽生菜的生产表现，实验设置3个重复组，为期45天。向鱼菜共生养殖池内的幼龄坦巴库鱼（tambacu）投喂商用配合饲料。监测水体水质并评估蔬菜生长状况。结果显示，相较于AquaFloc体系，Hydro组生菜的头径、株高、鲜重、干重、叶片数及叶绿素a+b浓度均显著更高（P<0.05），即便AquaFloc体系实验延长至60天仍未消除该差异。AquaFloc体系的鱼类存活率为62%，但其水体中氨氮与亚硝酸盐浓度显著低于Hydro组（P<0.05），且未检出硝酸盐。AquaFloc体系的电导率与水体总溶解固体浓度均显著低于Hydro组（P<0.05），但其水体pH值显著高于Hydro组（P<0.05），这导致植物可利用的营养元素有效性降低。基础鱼菜共生（Aqua）体系未出现生菜正常生长，且发生了鱼类全死亡的状况。本次实验采用的鱼菜配比未满足生菜的营养需求。未来需开展相关研究，采用适配的鱼菜配比并调控系统pH值，以为鱼菜共生体系中的植物提供充足的营养供应。