Nitrogen reduction and foliar application of zinc sulfate improve the physiological and biochemical characteristics of two autumn-sown sugar beet (Beta vulgaris L.)

Nitrogen (N) is considered as an important factor influencing sugar beet quantity and quality. Also, Zinc (Zn) is another main element to improve enzyme activity and growth of sugar beet. In fact, the balance between using top-mentioned elements can increased both sugar beet quantity and quality. The study aimed to look into nitrogen reduction and foliar zinc sulfate (ZnSO₄) administration to enhance the physiological and biochemical properties of two autumn-sown sugar beet cultivars (Beta vulgaris L.). The experimental treatments were two autumn cultivars of sugar beet (Rosagold and Chimene) and four fertilizer levels including N application based on soil test as 300 kg/ha and no foliar application of ZnSO₄ (control), and 10%, 20%, and 30% reduction in N application with foliar application of ZnSO₄ as 5 g/L. The Rosagold cultivar dramatically boosted leaf pigments, net photosynthetic rate, and soluble sugar of leaf under 10% reduction in N application with foliar application of ZnSO₄. Peroxidase, catalase, and sugar content were increased under applying Rosagold cultivar and 20% reduction in N application with foliar application of ZnSO₄. The effect of fertilizer levels on betaine was not significant, whereas a 10% reduction in N application with foliar application of ZnSO₄ reduced the α-amino-n. Overall, sugar beet quality and sugar content can be achieved using optimal management (i.e., by decreasing in N fertilizer with foliar application of ZnSO₄) and genetic (i.e., Rosagold cultivar) factors, and it could also be a step toward sustainable agriculture.