Impact of Calcium Sources and Application Methods on Micronutrient Content in Leaves and Fruits of High-density Apple Varieties

Background: Kashmir is famous for quality apples and overall higher production in India, but poor post-harvest storage infrastructure in region degrades its market acceptability. Maintaining calcium adequacy supply to plant is thus essential to enhance post-harvest shelf life and lessen the incidence of physiological disorders. Calcium use however declines few micronutrients availability in plant leaves and fruits. Objective: Evaluate effect of calcium use on micronutrient content in fruits and leaves of two apple varieties. Methods: Different calcium sources (calcium chloride and calcium nitrate), variable doses (3, 4 and 5 gram per liter of water in foliar spray and 100, 200 and 300 gram per plant in soil application), and their mode of application (soil and foliar) on two apple varieties (Golden Delicious and Red Chief Camspur) comprising 24 treatment combinations were tested. Results: Foliar application of calcium nitrate is an effective method for reducing drastic decline of essential micronutrient content particularly iron, zinc and boron in fruit and leaves of apple compared to its soil application or foliar application of calcium chloride, later two strongly reduces micronutrient content beyond required limits in both fruits and leaves if used at higher doses. The partitioning of micronutrients particularly iron, zinc and boron decreased with every increased dosage of calcium in plant leaves and fruits in both varieties. Micronutrients significantly declined over control and this decrease was reliant on calcium sources, dosage, and mode of application. Results of research revealed that at higher doses of calcium the iron, zinc and boron content in leaves of apple declined below 150, 41 and 35 ppm respectively, whereas respective micronutrient decline in fruit was below 1, 0.5 and 1 ppm respectively. Our study did find adversity of dosage and mode of application in maintaining required zinc, iron and boron content of fruit and leaf over control particularly in 5 gram per liter of water in foliar spray and 300 gram per plant in soil application. Conclusion: Orchardist cannot neglect importance of calcium use in apple for enhancing its shelf life, but instead of using calcium chloride use of calcium nitrate is better option to meet required calcium demands of apple. Alternate sprays of micronutrient mixture containing zinc, iron and boron is recommended to meet desired concentration of these micronutrients in fruit for better nutritive value.