The Effects of Slope and Channel Nutrient Solution Gap Number on the Yield of Tomato Crops by a Nutrient Film Technique System under a Warm Climate

Abstract

Inadequate oxygenation of the nutrient solution (NS) in recirculating hydroponic systems leads to root hypoxia in several plants as a result of low oxygen solubility, and this is most notable in warm climates. Hypoxia affects crop nutrient and water absorption and results in reduced crop yield. However, increased air supply to the NS serves as a source of oxygen for the roots. To evaluate the incorporation of oxygen into the system, we varied the slope of 14-m long containers from 2% to 4% and applied zero, one, two, or three gaps of NS. The channel width measured 10 cm and was equidistant from the end points. The effect of the dissolved oxygen in the NS was measured by the production of a tomato cultivar. The oxygen dissolved in the NS was 5% greater in the channels with a 4% slope compared with those with a 2% slope. The channels that included the gaps incorporated a higher quantity of dissolved oxygen during cultivation. In the middle of the day, the available oxygen was the limiting factor for the yield. The best results were obtained with a steeper slope, and gaps also improved the tomato yield. More rapid changes in NS were associated with a higher quantity of dissolved oxygen.