Calcium

Abstract

Calcium alone or with boron was supplied by trickle irrigation to ‘Topred’ and ‘Redspur’ strains of ‘Delicious’ on 4 rootstocks (Seedling, Malling‐Merton 104, 106 and 111) in 1977–80. Treatments were (1) water only, (2) Ca as CaCl₂ and (3) Ca+B as CaCl₂ and Na₂B₄O₇, added at rates of 50 and 1 g/tree/day for Ca and B, respectively, over 100‐day periods each year. Only treatment 3 with Ca and B reduced corking and increased fruit with no spots by 7.2% compared to water only. This was associated with overall increases in leaf, peel, and flesh Ca of 14, 13 and 8%, respectively (with rootstock interactions), and increases in leaf, peel and flesh B of 90, 265 and 337%, respectively, when compared to the check. The Ca treatment enhanced leaf Ca but not peel or flesh Ca. Addition of B to Ca enhanced peel and flesh Ca but not leaf Ca. Trees on MM‐106 rootstocks had higher leaf Ca than those on other rootstocks regardless of treatment but flesh Ca and corking severity were not affected. Trees on MM‐104 rootstocks had the lowest Ca uptake and the highest degree of corking. Increases in leaf Ca through the season were greater in treatments involving Ca. Yearly differences in corking severity had some association with fruit size and Ca levels, but data were inconsistent.

Key words:

• Leaf
• peel and flesh analyses

Notes

Authorized for publication as Paper No. 99 in the Department of Horticulture Series and as Paper No. 7457 in the Journal Series of the Pennsylvania Agricultural Experiment Station.

Professor of Plant Nutrition, Professor of Agricultural Engineering and Associate Professor of Pomology, respectively. The Pennsylvania State University, University Park, PA 16802.