Pomelo quality benefits and postharvest trade-off from oyster shell amendment for pH remediation

Soil acidification threatens citrus quality in southern China. This study evaluated oyster shell byproducts as a sustainable amendment to improve pomelo quality. Multi-site gradient trials combined with full-cycle monitoring over 260 days, including developmental and postharvest stages, identified moderate application (2 kg plant^-1) as generally optimal. Quality gains were stage-specific: improvements in sugars, vitamin C, and antioxidants were most pronounced during early to middle development and stabilized at maturity. Postharvest assessment showed that moderate amendment delayed sugar degradation and vitamin C loss for up to 90 days. However, these benefits were accompanied by aggravated juice sac granulation, indicating a rate- and time-dependent trade-off between compositional gains and structural stability. Overall, the results demonstrate that targeted acidity alleviation, rather than maximal pH elevation, is an effective strategy for balancing fruit quality and storage stability while enabling sustainable recycling of marine byproducts.