Effects of foliar fertilizer additives on grape fruit quality and endogenous hormones in leaves.

Background: Foliar fertilizer adjuvant is a fertilizer adjuvant that can improve the efficiency of plant leaf nutrient absorption. It is an effective means to reduce fertilizer usage and protect the environment, and plays an important role in agricultural production. However, under drought stress, traditional foliar fertilizers are susceptible to photolysis and evaporation loss, which affects the efficiency of nutrient absorption. This experiment used the 10-year-old grape 'Zitian Seedless' planted in the Wuwei area of the Hexi Corridor as the test material, focusing on foliar fertilizer adjuvants, and through its synergistic effect, explored the effects of potassium dihydrogen phosphate combined with different foliar fertilizer adjuvants on leaf endogenous hormones and fruit quality.

Method: This experiment had a total of six treatments: CK (potassium dihydrogen phosphate), T1 (potassium dihydrogen phosphate + ethylated and methylated vegetable oil), T2 (potassium dihydrogen phosphate + silicone), T3 (potassium dihydrogen phosphate + green citrus oil), T4 (potassium dihydrogen phosphate + sodium nitrophenolate aqueous solution), T5 (potassium dihydrogen phosphate + triacontanol solution + benzylaminopurine). The effects of different foliar fertilizer adjuvants on grape fruit quality and endogenous hormones in leaves were explored through a solar greenhouse experiment.

Results: Different foliar fertilizer adjuvants can improve the quality of fresh grapes, and each treatment significantly increased the content of soluble solids in the fruit. T4 (potassium dihydrogen phosphate + sodium nitrophenolate) had the best effect: the single fruit weight, Vc, tannin and anthocyanin content of the mature fruit increased by 52.55%, 64.68%, 24.97%, and 152.56% respectively compared with CK, and the organic acid content decreased significantly. At the same time, the total content of aroma substances reached 1188.90 µg·kg⁻¹, which was 86.25% higher than that of CK. The analysis of endogenous hormones in leaves showed that T4 treatment had the most significant effect on ZT at the inflorescence separation stage, and the most significant effect on SA, IAA and ABA at the expansion stage, which were 121.89%, 15.62%, 137.23% and 37.36% higher than those of CK at the same period. In addition, T4 treatment had the lowest drug cost and was more economical.

Conclusion: This study revealed the effects of different foliar fertilizer adjuvants on the fruit quality and endogenous hormones of 'Zitian Seedless' grapes. It provides an efficient and low-cost foliar fertilizer adjuvant application scheme for grape cultivation in the Hexi Corridor region, which has important practical significance for improving the economic benefits and sustainable development of the fresh grape industry.