The effect of magnetic water compared with saline water , nano-Mg at 100 and 200 ppm and nano-Zn at 50 and 100 ppm treatments and their combinations on lemongrass plants (Cymbopogen citratus L.) was studied during 2018/2019 and 2019/2020.
Vegetative growth parameters including plant height, number of tillers/ plant, leaf area, herb fresh and dry weights were greatly affected by both studied factors. Magnetic water treatments recorded the highest values of all vegetative growth parameters compared with saline water. However, all nanoparticles of Mg and Zn treatments were superior than control in promoting vegetative growth parameters and the treatments of 100 ppm nano-Zn and 200 ppm nano-Mg recorded the maximum values of vegetative growth parameters. The combined treatments showed that the highest values of vegetative growth measurements were obtained in plants irrigated with magnetic water and sprayed with 100 ppm nano-Zn, in both cuts In 1st and 2nd
seasons.
N, P, K and Mg contents were significantly higher in lemongrass plants irrigated with magnetic water than those irrigated with saline water. Moreover, the treatments of 100 ppm nano-Zn exhibited the highest significant values of N, P, K, whereas 100 and 200 ppm of nano-Mg treatments were superior in recording the highest values of Mg content, in the two seasons. The combination treatments of lemongrass plants irrigated with magnetic water and sprayed with 100 ppm nano-Zn or 200 ppm nano-Mg produced the richest values of N, P and K% D.W., whereas, the treatments of magnetic water combined with 100 or 200 ppm of nano-Mg produced the best Mg content.
A great effect of magnetic water irrigation on increasing Fe and Zn contents than saline water treatments. The treatments of 50 and 100 ppm of nano-Zn were more effective than control and other treatments in maximizing Fe and Zn levels.
The combined treatments of lemongrass plants irrigated with magnetic water and sprayed with 100 ppm of nano-Zn exhibited the highest values of Fe and Zn% D.W. in most cases. Additionally, total chlorophyll greatly increased in lemongrass plants irrigated with magnetic water than those irrigated with saline water, whereas the treatment of 200 ppm nano-Mg increased it than others. Interaction effect showed that, plants irrigated with magnetic water and sprayed with nano-Mg at 200 ppm exhibited the highest values of total chlorophyll.
Proline and glycine betaine contents were greatly decreased with magnetic water treatment compared with saline water. Meanwhile, all applied treatments were effective in decreasing the levels of both constituents than control, which considered a good indicator to alleviation of water salinity stress on lemongrass plants through magnetic water and nanoparticles of Mg and Zn applications. Finally, volatile oil %, was greatly increased in lemongrass plants irrigated with magnetic water, especially the treatment of nano-Zn at 100 ppm as compared of others in this respect in both cuts and the two studied seasons. The interaction between the two studied factors was significant which means that both factors act together in improving volatile oil content in lemongrass herb