The Effects of Foliar Nutrient Applications on Split, Yield, and Internal Fruit Quality of 'Wonderful' Pomegranate (Punica granatum L.)

Author

John Matthew Chater, California Polytechnic State University, San Luis ObispoFollow

DOI: https://doi.org/10.15368/theses.2015.160
Available at: https://digitalcommons.calpoly.edu/theses/1510

Date of Award

12-2015

Degree Name

MS in Agriculture - Crop Science

Department/Program

Horticulture and Crop Science

Advisor

Lauren Garner

Abstract

Fruit split is the most important physiological disorder in pomegranate production, causing devastating crop losses worldwide. Foliar nutrient applications have been used experimentally to mitigate pomegranate fruit split but none have been conducted using the industry standard cultivar, Wonderful, and little is known about the effects of foliar nutrient applications on pomegranate. Additionally, investigations into putative health benefits of pomegranate fruit have increased interest in its production but limited evidence exists regarding effects of agricultural practices such as foliar fertilizer applications on internal fruit quality. ‘Wonderful’ pomegranate trees at 2 commercial orchards were treated with foliar applications of ZnSO₄ (3000 mg∙L^-1, 4000 mg∙L^-1, or 5000 mg∙L^-1), MgSO₄ (1%, 2%, or 3%), KNO₃ (1%, 2%, or 3%), or deionized (DI) water (control). Fruit were analyzed for fruit split incidence, yield, fruit number per tree, fruit diameter, fruit mass, mass of all arils in fruit, mass of 100 arils, total soluble solids (TSS), titratable acidity (TA), antioxidant activity (AA), total phenolics (TP), and mineral nutrient concentrations of leaves and fruit. Foliar applications of MgSO₄ and ZnSO₄ resulted in significantly lower fruit split incidence. Treatments had no significant effect on fruit number per tree, fruit diameter, and mass, mass of all arils in fruit, or mass of 100 arils. Leaf N, K, S, Mn, and Zn were significantly affected by the treatments. TSS and TA were not affected significantly by treatments. AA ranged from 77.8-84.3 percent inhibition of 2,2’-diphenyl-1-picrylhydrazyl and TP ranged from 2489-3046 mg·L^-1 gallic acid equivalents, with some KNO₃ treatments significantly affecting these parameters. Fruit mineral nutrient concentrations were characterized and Zn-treated trees had greater fruit Zn concentrations. The results suggest that foliar ZnSO₄ or MgSO₄ could be used to decrease fruit split incidence and increase nutritional content of ‘Wonderful’ pomegranate and any of the three tested foliar nutrients could be applied as a foliar fertilizer without negatively impacting fruit yield, size, internal quality, bioactivity, or mineral nutrient concentration.