Correlations of Calcium Content of ‘Baldwin’ Apples with Leaf Calcium, Tree Yield, and Occurrences of Physiological Disorders and Decay1

Calcium (Ca) level of leaves sampled in mid- or late summer was closely related to peel Ca levels of mature apples ( Malus pumila Mill. cv. Baldwin). Ca content of fruit was directly related to fruit yield of the tree, cycling with biennial bearing. In 1971 bitter pit incidence could be predicted from either leaf or peel Ca; internal breakdown and decay were less predictable. In 1972 leaf Ca and peel Ca averaged, respectively, 27 and 17% higher than in 1971, accompanying increased yield. Little bitter pit, internal breakdown, or decay occurred, even at Ca levels correlated with high incidence rates the previous year. We concluded that Ca must be only 1 among several factors regulating these occurrences.