S06 - Session P2 - Oxygen-nanobubbles improve root growth and health of lettuce in hydroponics

Authors: Zhaolei Sun, Su Liu, Sunmeet Bhatia, Sunil Sapkota, Svetla Sofkova-Bobcheva *

Oxygen-nanobubbles (ONB) can be supplied in irrigation water or nutrient solution in hydroponic indoor systems using modern nanobubble agrotechnology. Nanobubbles also called ultrafine bubbles (less than 1μm in size) possess some unique properties which together with high dissolved oxygen concentration (%DO) content between 20 and 40 mg/L is suggested to improve plants' health, growth, yield, and quality. In this research, the effect of ONB on the plant growth, yield, and postharvest quality of commercial lettuce cultivars ( Lactuca sativa L.) grown in a Nutrient Film Technique (NFT) were studied. Four cultivars of lettuce namely, Chalmers, Meditation, Chicarita, and Tallio, were transplanted and grown for 50 days in a nutrient solution with a pH of 5.8 and an EC of 1 dS/m. A glasshouse trial was set up with two treatments, one was ONB irrigation with a target %DO of 20mg/L, and the other was control irrigation. The results showed that the root length of the four cultivars was significantly longer in ONB (average 599 mm) than in control irrigation (average 257 mm) with the biggest difference recorded for Meditation where a 126.5 % increase in root length was recorded. Yield indicators such as the number of leaves, fresh weight, and total leaf area were superior under ONB irrigation but with significant differences for Chalmers and Meditation only. That could be explained by the relatively short growing period of the lettuce crop. In terms of storage ability, the relative weight loss of the plants under ONB was significantly lower than that under control irrigation. ONB also contributed to the overall health of plants' roots due to suppression of algae growth throughout the hydroponic system and channels as well as on the roots of lettuce plants. Therefore, it could be concluded that ONB irrigation is beneficial for both root growth and the health of crops grown in NFT greenhouse systems, as well as indirectly improving the postharvest quality of lettuce. Further studies should focus on the effect of ONB on fruiting crops with longer growing periods like strawberries and tomatoes, as well as testing different %DO.