Temporal Variations in Photosynthesis and Leaf Element Contents of ‘Marselan’ Grapevines in Response to Foliar Fertilizer Application

The objective of this study was to examine the impact of various foliar fertilization treatments on the growth of new shoots, photosynthetic characteristics of leaves, and mineral nutrient content in the leaves of '<i>Marselan</i>' grapevines. Five distinct combinations of nano zero-valent iron (n ZVI), compound sodium nitrophenolate (CSN), and potassium dihydrogen phosphate (KH₂PO₄) were administered through foliar application to '<i>Marselan</i>' grapevines cultivated in the Wuwei region of the Hexi Corridor, with water spray serving as the control treatment. The results showed that T5 treatment (15 mg·L^-1 n ZVI + 0.4 g·L^-1 CSN + 2.5 g·L^-1 KH₂PO₄) significantly increased the leaf area and SPAD value of '<i>Marselan</i>' grapes; T4 treatment (15 mg·L^-1 n ZVI + 0.4 g·L^-1 CSN + 1.67 g·L^-1 KH₂PO₄) significantly increased the internode length of new grape shoots. T5 treatment was favorable to increase the basic coarseness of new grape shoots, the net photosynthetic rate of the leaves, and stomatal conductance; leaf transpiration rate was the highest under the T4 and T5 treatments; T3 (15 mg·L^-1 n ZVI + 0.4 g·L^-1 CSN + 1.25 g·L^-1 KH₂PO₄), T4, and T5 treatments could improve leaf initial fluorescence at different periods. At 45 days after flowering, the maximum photochemical efficiency under the T3 and T4 treatments reached the highest value throughout the period, and the T3 treatment improved leaf potential maximum quantum yield. Meanwhile, the leaf nitrogen and phosphorus content under the T5 treatment were the highest in the five periods. Additionally, the contents of potassium (K), manganese (Mn), copper (Cu), and zinc (Zn) in the leaves increased significantly under the T4 and T5 treatments. The following conclusions emerged from a comprehensive analysis: the T4 treatment was the best, and the T5 treatment was the second most effective.