Magnetic Iron–Improved Growth, Leaf Chemical Content, Yield, and Fruit Quality of Chinese Mandarin Trees Grown under Soil Salinity Stress

Chinese mandarin fruits are an inexpensive and rich source of vitamin C. They have potential benefits in treating acute respiratory infections and mitigating inflammation in critical patients with COVID-19. In Egypt, citrus is the most important fruit tree but is sensitive to salinity stress, resulting in poor vegetative tree growth and reductions in productivity and fruit quality. Magnetic iron has emerged as a promising approach in the citrus tree industry, since it improves vegetative growth, yield, and fruit quality and alleviates salinity stress in Chinese mandarin trees grown in soils suffering from high salt stress. This research is aimed at studying the influence of adding magnetic iron (as soil treatment) on tree canopy growth, yield, and fruit quality of ‘Chinese’ mandarin trees. Therefore, the treatments were as follows: 0, 250, 500, and or 750 g of magnetic iron.tree(−1). Our results indicated that all applications of magnetic iron significantly improved tree canopy volume, leaf total chlorophyll, relative water content, yield (kg.tree(−1)), and the fruit physical and chemical characteristics of Chinese mandarin. In contrast, leaf Na and Cl content, (%), proline, and total phenolic content were decreased by magnetic iron soil treatments. In respect to vegetative growth, our results indicated that adding magnetic iron at the concentration 750 g.tree(−1) caused the best values of tree canopy volume. A similar trend was noticed regarding yield. The increase in yield attained was nearly 19%; the best values were obtained when magnetic iron were used at 750 g.tree(−1). In conclusion, the application of magnetic iron can lead to improved fruit production and fruit quality of Chinese mandarin trees grown in salinity stress conditions.