Silicon fertilizations mitigate fruit cracking and enhancing yield and quality in reticulated melon (Cucumis melo L. var. reticulatus)

Fruit cracking and quality were key factors in the economic profitability of muskmelon. Silicon (Si) can improve fruit quality and reduce cracking, but its effects on melon crops remain understudied. This study investigated how two Si fertilizers—monosilicic acid (SiM) and “Lujia 1” (SiL)—affect cracking rate, yield, and quality in crack-resistant (‘Chun Honey 25’, C25) and crack-susceptible (‘Xizhou Honey 25’, X25) melon cultivars, compared to a no-Si control. Results showed that both Si fertilizers significantly reduced cracking rates (by 54.9–36.0% in X25 and 44.3–35.8% in C25), with SiL being more effective than SiM. SiL also increased yield more prominently, particularly in X25 (93.8 t ha⁻¹, + 28.1% vs. control). Both Si fertilizers enhanced sucrose accumulation by upregulating sucrose phosphate synthase activity while suppressing acid invertase, increasing soluble sugar content by 4.2–4.4%. Additionally, SiL boosted vitamin C content by 89.6% in X25 and 51.7% in C25, primarily by enhancing L-galactono-1,4-lactone dehydrogenase activity while reducing ascorbate oxidase and peroxidase activities. These findings demonstrate that Si fertilizers, especially SiL, mitigate fruit cracking, improve yield, and enhance sugar and vitamin C accumulation in melons by modulating key metabolic enzymes.