Cooling and concentration of nutrient solution in hydroponic lettuce crop

Abstract

The study was conducted in greenhouse at horticulture department of the Instituto Federal do Espírito Santo, Campus Itapina, Colatina, northwestern Espírito Santo state, Brazil, with the objective of evaluating the effect of cooling and electrical conductivity of nutrient solution on growth and development of lettuce cv. Vitória de Santo Antão in hydroponics. The study was conducted in a completely randomized design with two factors (control of the maximum temperature of the nutrient solution: 26ºC and without control; and electrical conductivity, EC, of the solution: 1, 2 and 3 dS m-1) with three repetitions. The plants were harvested fifty-two days after sowing (DAS). We evaluated the dry and fresh mass of leaves, stems and roots, stem and root length, root volume and plant water content (%). The temperature of the nutrient solution influenced the behavior of lettuce influenced by the electrical conductivity, showing that the increase of the EC did not reduce the lettuce productivity when the maximum temperature of the nutrient solution is limited, which in this experiment was tested at 26ºC. The cooling of the nutrient solution provided greater accumulation of mass and a higher water percentage in plants, increasing the productivity of hydroponic lettuce in tropical climate.

Hydroponic rocket salad growth and production according to different color profiles

“…This result may be related to variations in the root system optimum temperature for growth due to high temperatures and high incidence of light, causing a reduction in the growth rate, due to the increased temperature of the circulating nutrient solution in the root zone in black profiles. According to Cometti et al (2013), in hydroponic cultivation systems, the temperature of the nutrient solution is closely related to the amount of oxygen (O 2 ) dissolved in the solution. According to these authors, increasing the solution temperature results in a release of the O 2, reducing the respiration of the root system.…”

Effects of Nutrient Composition and Lettuce Cultivar on Crop Production in Hydroponic Culture

“…Easy control of nutrient composition, lack of soil contamination, faster plant growth, shorter crop cycles, high product quality, and good consumer acceptance have made hydroponics an important alternative plant production technique [7][8][9][10]. In tropical climates, a lettuce crop cycle is around 70 days in soil cultivation, whereas the duration is reduced to 30 days in hydroponic culture [11]. Plants grown in hydroponics contain more minerals and chlorophyll compared to those produced in a conventional soil-based system [12,13].…”

Levels of nitrate, pigments and thermographic analysis of lettuce under different temperatures of nutrient solution

“…This behavior is due to the increase of nutrient solution temperature, which results in increased electrical conductivity thereof. A higher electrical conductivity favors increased nitrate content in lettuce leaves, because the conductivity of the nutritive solution does not only influence the absorption of water, but also the absorption of nutrients, both of which are closely linked (Steidle et al, 2005;Genuncio et al, 2012;Cometti et al, 2013). Tr -Root temperature, Ts -Stem temperature, Tm -Temperature of the middle of the plant, Tex -Temperature of the extremity of the plant.…”