Study on the relationship between calcium nutrition and bitter pit in bagged apples

The bagged fruit of Fuji apple cultivar were used to study the relationship between the occurrence of bitter pit and the content of calcium and nitrogen in fruit. The changes of the content of calcium and nitrogen in the bagged young and mature fruit, the humidity in the bag and the incidence rate of bitter pit were examined regularly. Results showed that for non-bagged fruits,calcium absorption of young fruit accounted for 30% of the total fruit calcium content, and calcium absorption in late fruit development accounted for 70% of total fruit calcium content. Fruit bagging increased the humidity in the bag and reduced fruit transpiration, deceased calcium absorption. Meanwhile, nitrogen content in bagged fruit was consistently higher than that of non-bagged fruit, and N/Ca of bagged fruit was increased. Due to the mentioned factors the occurrence of bitter pit was induced. Applying organic substances to the soil in the apple orchards could improve the provision of Ca2+ in root zone and reduce the incidence rate of bitter pit.