Quantity and quality of lettuce (Lactuca sativa L.) grown by a circulating hydroponic method with a Halbach array magnetizer

The influence of the magnetic generator device on both the quality and quantity of lettuce (Lactuca sativa L.) grown by a circulating hydroponic method was investigated. The device was developed based on the engineering design process and subjected to simulation-based computational software. Tap water and nutrient solution flowed through magnetic fields generated by the device. Two groups of lettuce seeds were germinated initially in magnetized and unmagnetized water without the use of fertilizers. Each sprout group obtained from each water system was then cultivated with magnetized and unmagnetized nutrient solutions using the circulating hydroponic method. The physical characteristics of plants were investigated. Concentrations of elements, chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, and vitamin C in harvested leaves were analyzed. Results showed that magnetized water improved both the rate (5 plant·day−1) and percentage (94 %) of seed germination. The nutrient solution circulating through the device increased plant height (47.44 %), as well as the fresh (45.57 %) and dry (34.16 %) weights of plants. In addition, the magnetized nutrient solution increased the contents of elements (N: 7.86 %, P: 0.82 %, K: 5.74 %, Ca: 4.24 %, Mg: 9.33 %, Zn: 8.31 %, Mn: 8.82 %, Fe: 4.52 %), chlorophylls (a: 16.43 %, b: 26.30 %, total: 19.35 %), carotenoid (13.01 %), and vitamin C (2.87 %). Therefore, these observations indicated that applying the designed device to lettuce cultivation using the method of circulating hydroponic could improve both the quantity and quality of the lettuce.