The Effect of Foliar Calcium Treatments on Fruit Weight and Firmness of Rabbiteye Blueberry ( Vaccinium VirgatumAiton)

Abstract

Foliar calcium applications are used in many fruiting crops to minimize disease and physiological disorders. In blueberry ( Vaccinium spp), it is used to improve fruit firmness with varying success. Two applications of foliar calcium applied to rabbiteye blueberry ( V. virgatumAiton) cvs. Alapaha and Powderblue as calcium nitrate [Ca(NO ₃) ₂], neutralized calcium carbonate (CaCO ₃), and chelated calcium (calcium glucoheptonate, C ₁₄H ₂₆CaO ₁₆) were made at the label rate of 2.3 L·ha ^-1applied in a volume of 935.3 L·ha ^-1(697 ppm, 108 ppm, and 604 ppm Ca per application, respectively). The applications were made at 30 and 15 days preharvest in 2013 and 2014. Fruit were hand harvested at 40% ripe and evaluated for berry weight, color, firmness, soluble solids, and acidity. In 2013, fruit were stored at 1 °C with 85% relative humidity and evaluated again at 7 and 15 days. In 2014, fruit and tissue samples were evaluated for Ca concentration. In 2013, ‘Powderblue’ had a 5% increase in firmness from the CaCO ₃treatment when compared to control fruit. The chelated calcium treatment significantly increased fruit weight by 12% compared to the control for ‘Alapaha’. Fruit firmness increased 5% and fruit weight decreased 10% for the Ca(NO ₃) ₂treatment compared to control for ‘Alapaha’ fruit sampled after 2 weeks of storage. In 2014, none of the treatments significantly increased fruit firmness or berry calcium concentration. For ‘Powderblue’ in 2014, all treatments significantly decreased firmness. Leaf Ca concentration was increased by 18% for ‘Alapaha’ and decreased by 26% for ‘Powderblue’ when comparing the chelated calcium treatment to non-treated leaves.