Aquaculture America 2020

February 9 - 12, 2020

Honolulu, Hawaii

EFFECT OF AERATION ON WATER QUALITY, AND ROMAIN LETTUCE PERFORMANCE IN AQUAPONICS AND HYDROPONIC SOLUTION

 
Emmanuel Ayipio (M.Sc.)* and Daniel Wells (Ph.D.)
*Auburn University
Department of Horticulture ,
105 Funchess Hall,
36849-Auburn, Alabama .
eza0035@auburn.edu

Oxygen within the root zone is an important requirement to keep roots alive for enhanced nutrient uptake and plant growth. In water-based systems, oxygen of the water is maintained by blowing air through the water with the aid of diffusers or air stones . Where aeration is not maintained, di ssolved oxygen  (DO)  concentration (mg/l) reduces .  At very low DO, water quality parameters such as nitrates, pH, and electrical conductivity (EC) are greatly affected. These changes affect plant growth and productivity. The objectives of this study were  to  1) compare water quality of two nutrient sources in response to aeration and no aeration, 2) to assess the  growth, stomata conductance, SPAD and yield of Romain lettuce in the systems. The experiment was a 2x2 factorial arrangement in a randomized completed block design with four replicates. The results indicate that n o aeration led to a reduction in DO level in both aquaponics and hydroponics systems (1.12 mg/l and 3.46 mg/l respectively). No a eration  caused no statistically significant  change in EC for either system but led to  70 mg/l  reduction in  nitrate than aeration  in aquaponics. Additionally, n o aeration led to a  1 o C increase in temperature than the aerated for both systems  but decrease in pH by  1 unit  in  only aquaponics system. Generally, plant height decreased in no aeration  across systems whereas a verage SPAD value was higher by 3 units and 1 unit in no aeration than aeration aquaponics and hydroponics respectively. Leaf temperature and stomata conductance showed no statistically significant differences among the treatments. Although root length was statistically different between aeration and no aeration, root dry mass was not. Also, shoot weight per plant was about 50% and 29% more in aeration than no aeration for fresh and dry mass respectively . In conclusion, the study revealed that aquaponics-based system was more affected by a lack of aeration than hydroponics system. Also,  no aeration had more effect on productivity related traits than physiological related traits except SPAD of the lettuce plants. It was observed that no aeration reduced tipburn which is a major challenge in hydroponic Romain lettuce production. Therefore, no aeration should be explored further. Future research should introduce an oxygen zone around the root area.  This  might counter the negative effects of no aeration in deep water culture system.

Key Words : Dissolved oxygen, Electrical conductivity, Stomata conductance, leaf SPAD value, Deep water culture