Monitoring, calibration and maintenance of optimized nutrient solutions in curly lettuce (Lactuca sativa, L.) hydroponic cultivation

Abstract

The monitoring, calibration and maintenance of nutrient solutions are fundamental for the development of hydroponic lettuce. This study aimed to monitor temperature, electrical conductivity, hydrogen potential and consumption of nutrient solution, besides evaluating the effectiveness of the Microsoft Office Excel SOLVER tool in the calibration of different mineral and organomineral nutrient solutions in the NFT hydroponic cultivation of curly lettuce. The experiment was conducted in randomized blocks with three replicates and the treatments consisted of four mineral solutions proposed by Furlani, Bernardes, Ueda and Castellane and Araújo, besides four organomineral nutrient solutions, proposed in this research, with chemical composition similar to the previously cited ones. For 24 days, the nutrient solutions were monitored and the variations of temperature, pH, electrical conductivity (EC) and nutrient solution consumption by the crop were measured. Calibrations were made using the Microsoft Excel SOLVER tool, using as reference an EC of 1.5 dS m -1 and nutrient solution volume of 17 L. During the experiment, regardless of the nutrient solution (modified and mineral), temperature showed maximum and minimum values of 28.7 and 21.5 ºC, respectively, and pH variation was lower in the modified nutrient solutions. Water consumption was higher with the use of mineral solutions, in comparison to the organomineral solutions with the same chemical composition. The SOLVER tool was efficient and easily used in the calibration and maintenance of electrical conductivity and volume of the nutrient solutions.

Hydroponic Cultivation of Coriander Using Fresh and Brackish Waters With Different Temperatures of the Nutrient Solution

“…Plant nutrient uptake depends on the temperature of the nutrient solution because it directly affects nutrient absorption. The effect of temperature on nutrient uptake cannot be generalized, as these effects vary depending on the physiological processes and organs of plants (Yan et al, 2012), and can cause phytosanitary and nutritional problems in plants, mainly due to the low availability of oxygen to the roots (Monteiro Filho et al, 2018). According to Sakamoto et al (2016) and Al-Rawahy et al (2019), the dissolved oxygen concentrations has an inverse relationship with the temperatures of the nutrient solutions, that is, oxygen availability decreases in the plant rhizosphere with increasing solution temperatures, as observed in a previous experiment with coriander (Silva et al, 2020b).…”