Foliar feeding of citric acid mitigates artificial urine and NaCl-induced saline stress in hydroponic sugar beets

In lunar and deep-space farming, saline stress (SS) induced by human urine in hydroponically grown vegetables constitutes one of the prime concerns in its utilization for plant nutrition.Therefore, an indoor hydroponic trial was performed to assess the effectiveness of foliar feeding of citric acid (CA, 50 M as two sprays at 26 days and 38 days after germination using a common hand-held sprayer) and the control treatment (a standardized plant nutrient with 10% synthetic urine replacement and 50 mM NaCl-induced SS) for sugar beets.The response variables included vegetative growth traits of sugar beets, such as the height of plants and stem girth along with lengths and fresh weights of leaves, roots, and whole plants.The recorded findings demonstrated that at the fourth week of germination, CA foliar feeding did not produce a statistically significant impact on the leaf width and plant height of sugar beets.However, CA produced 17%, 14%, and 35% taller plants at the six, eight, and ten weeks of germination, respectively.Likewise, the control treatment recorded 32% and 30% smaller leaf widths of sugar beets compared to the CA foliar feeding treatment at the 8 th and 10 th weeks of germination, respectively.In addition, it was found that CA foliar feeding was effective in enhancing the stem length and root length by 16% and 38%, respectively compared to the control under SS.Moreover, CA foliar feeding enhanced stem diameter (26%) and root fresh weight (29%) compared to the control treatment.As far as leaf length and fresh weight along with whole plant fresh weight were concerned, foliar feeding of CA demonstrated its effectiveness by producing 32%, 21%, and 42% greater values, respectively compared to the control treatment.Therefore, CA foliar feeding could serve as a potent strategy to mitigate the deleterious effects of saline stress and boost the vegetative growth of hydroponically grown sugar beets.