Effects of greenhouse cultivation on fruit quality and mineral nutrition in loquat fruit

Abstract：【Objective】Jiangsu province is the northern edge of loquat cultivation. Greenhouse cultivation can not only alleviate or avoid the freezing injury frequently occuring in the open-field cultivation, but also improve the quality of loquat fruit, advance loquat maturation and increase the profit. The aim of this research is to explore the effect of greenhouse cultivation condition on quality and mineral elements in loquat in order to provide reference for scientific fertilization in greenhouse.【Methods】Mineral nutrition is the material basis of fruit tree growth and yield and quality formation. Studying the dynamic change patterns of mineral nutrients during growth and development is helpful to understand the absorption and utilization characteristics of the nutrient elements in the tree and fruit. Trees of Eriobotrya japonica‘Baiyu’cultivated in greenhouse and in open field in Zhangjiagang, Jiangsu province were used as the experimental materials. Leaf, flower and fruit samples were collected at flower bud dif-ferentiation period, flowering period, young fruit period, fruit expanding period and fruit maturation period, and the mineral nutrient contents in the samples and fruit quality were determined. Data were analyzed using SPSS and EXCEL. Significant differences in loquat fruit quality indexes between the two cultivation modes and its correlation to mineral elements in the leaves, flowers and fruit were analyzed. 【Results】(1) The single fruit weight, fruit shape index, pulp thickness and solid/acid ratio in trees cultivated in greenhouse were significantly higher than those cultivated in open field, but titratable acid was significantly lower, which shows that greenhouses cultivation can obtain better fruit quality. (2) The dynamics of nine mineral elements in the leaves, flowers and fruit of‘Baiyu’cultivated in greenhouses and in open fields were basically the same throughout the growth and development. Under at the same level of management and berry load, the average contents of N, Ca, Mg, Cu and Zn in the leaves, the N, P, K, Ca, Mg, Fe, Mn and Cu contents in the flowers and the N, P, K, Ca, Mg, Cu and Mn contents in the fruit were higher in the greenhouse than in the open field. Under the greenhouse cultivation conditions, from flower bud differentiation stage to flowering stage, the elements of N, Ca, Mg, Cu and Zn in the leaves showed a downward trend, while the other elements showed an upward trend; the N, K and Mn in the flowers showed an upward trend, while the other elements showed a downward trend. From young fruit stage to the fruit maturation, the contents of N, P, K, Ca, Mg, Mn, Cu and Zn in the leaves decreased with fruit development. (3) The results of correlation analysis showed that N content in the leaves was strongly negatively correlated with N content in the flowers; Ca, Mg, Fe, Mn, Cu and Zn contents in leaves were significantly positively correlated with the corresponding mineral element content in the flower. The contents of P, K, Ca, Mg and Mn in the leaves were significantly positively correlated with the corresponding mineral elements in the fruit; while the contents of Cu in the leaves were significantly negatively correlated with those in fruits. The contents of Ca and Zn in the leaves and the contents of Mg, Mn and Cu in fruit were significantly positively correlated with fruit weight and soluble solids, but negatively correlated with titratable acid content. The contents of Fe and Mn in the leaves and the content of Fe in the fruit had strong negative correlations with fruit weight and soluble solids, but were strongly positively correlated with titratable acid content.【Conclusion】In summary, compared with the open field cultivation, the greenhouse cultivation significantly improved the quality of loquat fruit, and loquat cultivated in greenhouse has a large demand for mineral elements. Ca, Fe, Mn and Zn in the leaves and Mg, Fe, Mn and Cu in fruit might have a significant impact on fruit quality. It is suggested that for loquat cultivation in greenhouse, the overall fertilization rate should be increased appropriately. At the same time, quality of loquat fruit under greenhouse cultivation could be increased by increasing the contents of Ca and Zn in the leaves and Mg, Cu and Mn in the fruit via foliar application.