Synergistic effects of compost amendment and foliar nano-micronutrients on yield and quality of sugar beet grown in calcareous soil

Calcareous soils, characterized by high pH and low nutrient availability, pose significant challenges to sustainable sugar beet production. Combining organic soil amendments with advanced nano-fertilizers may offer a synergistic strategy to enhance crop productivity and quality in such marginal environments. A 2-year field study (2022/2023 and 2023/2024) was conducted using a split-plot design to evaluate the effects of three compost rates (0, 3, and 6 tons acre−1) and five foliar nano-micronutrient combinations (control, Fe + Mn, Fe + B, Mn + B, Fe + Mn+B applied at 100 mg L−1 each). Growth, physiological, yield, and technological quality parameters of sugar beet were analyzed. The integrated application of 6 tons compost acre−1 and the nano Fe + Mn+B mixture resulted in powerful synergistic effects, consistently outperforming all other treatments. This optimal combination maximized photosynthetic pigments (e.g., increased chlorophyll a by 27%), boosted antioxidant enzyme activities (catalase by 29%, peroxidase by 42%), and enhanced growth parameters, leading to a 55% greater leaf area index. Consequently, it achieved the highest sucrose content (up to 19.85%), extracted sugar percentage (17.25%), root yield (27.12 tons acre−1), and sugar yield (4.68 tons acre−1), representing yield increases of 28–32% and 63–69%, respectively, over the compost-only control. For optimal sugar beet productivity in calcareous soils, an integrated management approach is recommended, consisting of soil amendment with 6 tons of compost per acre supplemented by foliar application of a combined nano-iron, manganese, and boron mixture. This strategy effectively enhances soil health, plant physiological performance, and ultimately, sugar yield and quality, providing a sustainable pathway for cultivation in nutrient-deficient calcareous environments.