Abstract:

To investigate the application effect of fulvic acid potassium on mountain apples in Yan’an, an experiment was carried out from March to November 2023 at the mountain apple base of Golden Land Agriculture and Animal Husbandry Co., Ltd. in Yanchang County. The test apple was ‘Yuhua Zaofu’ with a tree age of 12 years. Different application rates of fulvic acid potassium were applied during the fruit expansion stage, with the conventional fertilization by farmers as the control, to analyze its influence on the absorption of nitrogen, phosphorus and potassium nutrients, as well as the yield and quality of apples. Compared with the control, there was no significant difference in the leaf N, P and K contents under the treatment of 20% increment of fulvic acid potassium (2.6 kg/plant) during the young fruit stage. However, during the fruit expansion stage, the leaf N, P and K contents increased by 44.61%, 257.89% and 44.55% respectively, and during the maturity stage, they increased by 24.85%, 95.31% and 29.98% respectively. Under the treatments of 20% decrement (1.4 kg/plant), conventional amount (2.0 kg/plant) and 20% increment of fulvic acid potassium, the fruit N, P and K nutrient uptake increased by an average of 13.64%, 7.59% and 34.38% compared to the control. The vitamin C content increased by 61.65%, 104.56% and 115.15% respectively, the soluble sugar content increased by 14.66%, 40.69% and 25.73% respectively, and the titratable acid content decreased by 3.70%, 22.22% and 29.63% respectively. The fulvic acid potassium treatments could significantly enhance the fruit firmness, soluble solids content, single fruit weight and the yield per plant. Compared with the control, the treatments of 20% decrement, conventional amount and 20% increment of fulvic acid potassium increased the yield per plant by an average of 3.86%, 6.05% and 10.20% respectively. On the basis of conventional fertilization, applying 2.6 kg/plant of fulvic acid potassium during the fruit expansion stage can effectively improve the yield and quality of Yan’an mountain apples.

Key words: apple, fulvic acid potassium, mountain apple, reduced fertilization, nitrogen, phosphorus and potassium nutrients, nutrient uptake, quality, yield