Integrated Application of K and Zn as an Avenue to Promote Sugar Beet Yield, Industrial Sugar Quality, and K-Use Efficiency in a Salty Semi-Arid Agro-Ecosystem

Salinity combined with a deficiency of potassium (K) and zinc (Zn) negatively affect sugar beet yield and quality. A two-year (2017/18-2018/19) field trial was undertaken to investigate the mediating role of soil-applied K [120 (K-120) and 180 (K-180) kg ha(-1)] and foliar-applied Zn [0 (Zn-0), 150 (Zn-150), and 300 (Zn-300) ppm] in alleviating salt-stress (8.60 dS m(-1)) based on sugar beet morpho-physiological responses, sugar yield and quality, and K-use efficiency in the BTS 301 and Kawemira cultivars. Application of K-180 x Zn-300 was more effective and resulted in 23.39 and 37.78% higher root yield (RY) and pure sugar yield (PSY), respectively, compared to control (K-120 x Zn-0). It also enhanced sucrose, pure sugar (PS), and purity but decreased impurities (alpha-amino N, K, and Na), alkalinity index, and sugar loss. However, the K-120 x Zn-300 recorded higher K-use efficiency. PSY correlated positively (r = 0.776 **, 0.629 **, 0.602 **, 0.549 **, and 0.513 **) with RY, root fresh weight (RFW), top yield, PS, and root diameter, respectively. The stepwise and path-coefficient analysis demonstrated that RY, PS, and RFW were the most influential PSY-affected attributes. Integration of K-180 + Zn-300 can correct K and Zn deficiencies in the soil and mitigate salt-stress effects via improving sugar beet growth, yield and quality, and K-use efficiency.