Effect of magnesium application on the fruit coloration and sugar accumulation of navel orange (Citrus sinensis Osb.)

Magnesium (Mg) deficiency is a major factor limiting citrus production. Here, we performed Mg treatments (0, 100, 150, 200 and 250 g MgO plant-1) on 15-year-old navel orange (Citrus sinensis Osb.) trees to investigate the effect of Mg application on fruit yield and quality. Mg application obviously enhanced the fruit yield of navel orange, particularly at the dose of 150 g MgO plant-1, which significantly improved the fruit yield by 27.87% in 2019 and by 17.89% in 2020 compared with the control. At the fruit color turning stage, Mg application increased the sucrose content in the pulp, especially at the doses of 150 and 200 g MgO plant-1, which signif-icantly increased the sucrose content by 20.38-29.85% and 7.01-7.36% in 2019 and 2020, respectively. Moreover, application of Mg fertilizer significantly decreased the Chl a and total Chl contents in the peel, as well as increased the peel brightness and chroma, accelerated fruit ripening. Furthermore, the pulp sucrose content was negatively correlated with Chl a and total Chl in the peel. Overall, we proposed a recommended amount of Mg fertilization (142 to 177 g MgO plant-1) for high yield and good quality of navel orange fruit.

Automated summary

This study found that the application of magnesium fertilizer at the appropriate dosage can significantly improve the yield and quality of navel oranges. The best results were achieved with a dosage of 150 g MgO per plant. The application of magnesium fertilizer increased the sucrose content in the pulp and decreased the chlorophyll content in the peel, promoting fruit ripening.