Effect of foliar fertilizer on fruit yield and quality of Chaenomeles speciosa (Sweet) Nakai based on principal component analysis

Abstract:【Objective】Chaenomeles speciosa is known as the“fruit of a hundred benefits”and has great market potential. Improving fruit yield and quality in cultivation is the core of improving market competitiveness. Proper fertilization is one of the important measures to improve fruit yield and quality. However, in actual production, the use of micronutrient fertilizer is often neglected in favor of large amount of elemental fertilizer. Trace element fertilizer is an important factor affecting the yield and quality of fruit. This study aims to elucidate the effects of foliar spraying of calcium (CaCl2), magnesium (MgSO4) and boron (borax) fertilizers at different concentrations on C. speciosa fruit yield and quality, to explore the best fertilizer concentrations of CaCl2, MgSO4 and borax solutions to improve C. speciosa fruit yield and quality, and to provide reference for reasonable foliar fertilizer spraying on C. speciosa.【Methods】Three year old C. speciosa (Thouin) Koehne Changjun was used as the test material, and different concentrations of CaCl2, MgSO4 and borax solution fertilizers were sprayed during fruitdevelopment. The three levels set for CaCl2 were 0.1%, 0.2%, and 0.3%; those for MgSO4 were 0.5%, 1.0%, and 1.5%, and for borax 0.1%, 0.2%, and 0.3%, with spraying water as the control. The foliar fertilizers were sprayed on the fruit and leaves until drip for three times after 16:00 on a sunny day without wind. Other cultivation management was carried out according to normal field management. After fruit ripening, fruit of good shape and uniform maturity, free from obvious pest and mechanical damage were randomly selected to determine the main indexes of fruit yield and quality under different treatments. The fruit yield, appearance quality, taste quality and nutritional quality were compared, and finally, the yield and quality of C. speciosa fruit were comprehensively evaluated using correlation analysis and principal component analysis.【Results】Foliar sprays of different concentrations of calcium, magnesium and boron fertilizers all improved fruit yield and quality to varying degrees compared to the control. ANOVA results showed that the differences in fruit set per plant, SOD enzyme activity, acid to soluble soilid ratio, and contents of starch, pectin, flavonoids, oleanolic acid, vitamin C, amino acids, soluble solids, titratable acid and tannins were highly significant (p＜0.01), and the differences in total fruit yield per plant, water content, soluble sugar content were significant (p＜0.05). The differences in fruit protein content, average fruit weight per plant, longitudinal diameter, transverse diameter, fruit weight per plant and fruit shape index were not significant (p＞0.05). Among them, spraying 0.1% CaCl2 had the highest fruit water content with an increase of 1.25% compared with the control; 0.2% CaCl2 treated fruit had the lowest tannin content, with a decrease of 58.22%; 0.3% CaCl2 treated fruit had the highest amino acid, flavonoid and protein contents, with increases of 25.36%, 42.86% and 12.19%, respectively; 0.5% MgSO4 resulted in the highest total yield and the highest fruit set, with increases of 81.21% and 53.45%, respectively; 1.5% MgSO4 had the highest fruit starch content and SOD activity, with increases of 41.95% and 156.57%, respectively; the treatment of 0.1% borax had the highest fruit pectin content, with an increase of 145.69%; 0.2% borax resulted in the lowest titratable acid content, with a decrease of 23.71%, and the highest vitamin C and soluble sugar contents with increases of 44.44% and 26.59%, respectively; fruit in 0.3% borax treatment had the highest fruit longitudinal diameter, transverse diameter, single fruit weight, average single fruit weight, solid to acid ratio, soluble solids and oleanolic acid content, with increases of 31.11% , 29.94% , 85.94% , 45.59% , 48.99% , 11.16% and 102.00%, respectively. The solid to acid ratio was negatively correlated with titratable acid content (p＜ 0.01), and was positively correlated with single fruit weight, longitudinal diameter, soluble solids, vitamin C and oleanolic acid (p＜0.01), and with SOD enzyme activity (p＜0.05). Correlations were also found among the remaining traits. To accurately evaluate the combined effect of the different treatments on yield and quality, principal component analysis was performed. The results showed that order of the treatments based on their effect on fruit yield and quality from the best to the worst was 0.3% B＞0.5% MgSO4＞0.2% CaCl2＞0.3% CaCl2＞0.1% B＞1.5% MgSO4＞0.2% B＞1.0% MgSO4＞0.1% CaCl2＞ CK. The overall scores were higher than CK, indicating that calcium, magnesium and boron fertilizers at tested concentrations were all beneficial to the improvement of fruit yield and quality, with 0.3% borax having the best overall enhancement effect.【Conclusion】Considering the comprehensive yield and quality factors, foliar spraying of 0.3% borax, 0.5% MgSO4, and 0.2% CaCl2 solution fertilizer during C. speciosa fruit development is recommended.