Growth and Yield Comparison of Lettuce, Basil and Tomato Grown in Aquaponics and Hydroponics Systems
Aquaponics is a production system that integrates aquaculture and hydroponics by recirculating residual nutrients resulted from fish waste for cop production. Although many different crops have been tested in aquaponics systems, limited information is available on the growth and yield of a crop grown in aquaponics compared to hydroponics. The objective of our research was to evaluate growth and yield of vegetable crops grown in aquaponics in comparison to hydroponics. Two leafy vegetables, lettuce (Lactuca sativa) and basil (Ocimum basilicum), and one fruity vegetable, cherry tomato (Solanum lycopersicum), were grown in both aquaponics and hydroponics systems. Each aquaponic unit consisted of a 378L fish tank with stocking density of 26kg/m3 Nile tilapia (Oreochromis niloticus L.) and a 378L growth bed with vegetable crops at the recommended planting density. The pH was monitored daily and adjusted to target levels (pH 7 in aquaponics and pH 6 in hydroponics). Measured EC averaged at 0.7 dS/cm in aquaponics while it was maintained at 2.0 dS/cm in hydroponics. The growth, yield, SPAD values and other morphological parameters were assessed during a 5-month production period. The results showed that marketable yield of hydroponically grown lettuce was significantly higher (P <0.05) compared to aquaponically grown one, while there were no significant differences in marketable yields of basil and tomato grown in both systems. Interestingly, aquaponic tomato produced significantly lower (P <0.05) fresh weight of stem and leaves but larger roots compared to hydroponic tomato, indicating that limited nutrients in aquaponics reduced shoot growth without affecting yield of tomato fruits. The SPAD values were higher in aquaponically grown vegetables although leaf parameters were not significantly different from hydroponically grown ones. It is concluded that the growth and yield of different vegetable crops are differently affected by production system, and therefore, a careful consideration is needed in determining vegetable crops suitable for the production in aquaponics system.