Effects of macronutrient application rates during fruit development on the yield, quality, and physiological disorders of Musang King durian (Durio zibethinus Murr.)

Physiological disorders are a major constraint affecting fruit quality and market value of Musang King durian, especially under Vietnamese agroecological conditions. However, the influence of different NPK application rates during fruit development on physiological disorders, yield, and fruit quality remains poorly understood. This study was conducted during 2024 at Can Tho University, Vietnam to determine appropriate macronutrient fertiliser application rates during fruit development and to clarify their effects on yield, fruit quality, and physiological disorders in seven-year-old Musang King durian trees. The experiment was arranged in a randomized complete block design with four macronutrient application rates (0.5, 0.75, 1.0, and 1.25 kg/tree/application) and five replications. Fertilizers were applied at three fruit development stages using different N:P:K ratios: 2:1:1 at 30 days after fruit set (DAFS), 2:1:3 at 45 DAFS, and 1:1:3 at 60 DAFS. The results showed that increasing NPK rates (1.0–1.25 kg/tree/application) significantly increased individual fruit weight and yield but also intensified the incidence of physiological disorders. In contrast, applying NPK at 0.75 kg/tree/application reduced the incidence of physiological disorders by 43–55% while maintaining high yield and superior fruit quality.