Exogenous Micronutrients Modulate Morpho-physiological Attributes, Yield, and Sugar Quality in Two Salt-Stressed Sugar Beet Cultivars

Exogenously applied micronutrients (M) have been reported to boost salinity tolerance and improve yield and quality. However, very little is known about the effect of M mixture foliar application under saline soil condition. Our objective was to investigate the influences of M mixture foliar application on morpho-physiological traits, yield, and quality and nutritional status of sugar beet under saline (9.39 dS m−1) soil. Two consecutive (2018/2019–2019/2020) field trials were conducted on both Romulus and Francesca sugar beet cultivars treated with M mixture (0 ppm; [M0], 150 ppm [M150; 75 Fe (FeSO4), 50 Zn (ZnSO4), 25 Mn (MnSO4)], and 300 ppm [M300; 150 Fe (FeSO4) 100 Zn (ZnSO4), 50 Mn (MnSO4)]. M150 or M300 significantly boosted growth, water status, photosynthetic efficiency, nutritional status, and productivity of sugar beet. M300 increased root yield (RY) by 11.5% and 42.0% and true sugar yield (TSY) by 22.7% and 92.9% compared to M150 and M0, respectively. M300-treated plants had higher sucrose, true sugar, and quality index but lower loss sugar and non-sugar impurities M300 markedly improved sugar beet performance owing to increase leaf hydration status, photosynthetic efficiency, nutrients (K+, Fe2+, Zn2+, and Mn2+) uptake, and K+/Na+ ratio. Romulus exhibited enhanced growth, yield, and quality, reflecting more salt tolerance when compared with Francesca. Stepwise regression indicated plant fresh weight, SPAD chlorophyll, and leaves number plant−1 are the most influential RY- and TSY-attributed characteristics in salt-stressed sugar beet. M150 or M300 are more effective and may offer a potential economic alternative for salinity-stress alleviation in salt-stressed sugar beet.