Salinity inhibits the uptake of nitrogen, which slows down the
growth and prevents plant reproduction. Certain ions, especially chloride, are poisonous to plants; when their concentration increases, the plant becomes poisoned and eventually perishes. The adaptability of several table beet cultivars (Beta vulgaris L.) to saline water irrigation creates new opportunities for extending
beet production, increases the added economic value, and has a positive environmental impact. A pot experiment is carried out for two successive seasons, 2019/2020 and 2020/2021, to investigate the effect of irrigation with agriculture saline drainage water on the growth and biochemical traits of three selected cultivars (Detroit Dark Red, Red Ball, and Red Ace). Four levels of salinity are applied (1000, 2000, 3000, and 4000 ppm) along with tap water of 260 ppm salinity, which serves as the control. Detroit Dark Red beets show the best results among the other cultivars under consideration. Irrigation with the first level of saline water (1000 ppm) at both seasons of cultivation results in a significant increase rate in growth parameters (13−23%). The second level of salinity (2000 ppm) shows the maximum increase rate of some chemical constituents, such as ascorbic acid (16.26%), nitrogen (58.21%), phosphorus (11.94%), potassium (34.66%), and sodium (85.14%). The levels of total soluble solids (TSS), anthocyanins, proline, total sugars, water saturation deficit, and sodium increase significantly in proportion to saline water concentrations. The selected table beet mature leaves show slight variations in anatomical structure, especially in the B. vulgaris L. cv. Detroit Dark Red under the highest salinity concentration (4000 ppm) was less than that of the control and the other two cultivars. Other cultivars may be the subject in the near future to study the effect of their salinity tolerance with the aim of increasing productivity, enhancing their characteristics, and preserving the environment.