OXYGENATION OF THE RECIRCULATING NUTRIENT SOLUTION AND ITS EFFECT ON TOMATO AND LETTUCE

Abstract

The inadequate oxygenation of the nutrient solution affects the absorption of nutrients and water, and consequently affects plant growth and development. In this study, the incorporation of oxygen in a recirculating hydroponic system by two passive methods, container inclination and hydraulic jumps, was evaluated in the tomato (Lycopersicon esculentum L.) and lettuce (Lactuca sativa L.) crops. Containers of 24 m long were used with 2 and 4 % inclination, and zero to three falls as hydraulic jumps of the nutrient solution. Dissolved oxygen in each hydraulic jump was measured at nutrient entrance and exit of the containers. Plant fresh weight, root dry weight and root volume were measured in both plant species, while fruit fresh weight only in tomato. In lettuce, the maximum plant fresh weight was obtained in containers with 4 % slope and three hydraulic jumps. In tomato, fruit weight was higher in containers with 4 % slope and two or three hydraulic jumps.