Leaf and fruit mineral content and peel thickness of 'Hamlin' orange

Kelly T. Morgan, Robert E. Rouse, Fritz M. Roka, Stephen H. Futch, Mongi Zekri


There were reports in late December 2004 that the number of split fruit in 'Hamlin' oranges [Citrus sinensis (L.) Osbeck] was higher than in previous years. Such reports included several loads, which were mechanically harvested and rejected at the juice plant because of split fruit. There were also reports of rejected trailer loads from hand-picked blocks. Initial visual inspection of the fruit in the affected groves indicated that the peel thickness of 'Hamlin' oranges appeared to be thinner than usual. Previous studies have demonstrated positive correlations among fruit size, peel thickness and tree nutrition. Fruit samples from trees on three rootstocks were collected from seven locations in the Immokalee area. Along with fruit size, juice quality, and peel thickness measurements, samples of the juice and dried peel were analyzed for calcium (Ca), phosphorus (P), and potassium (K) for each rootstock and location. There were significant differences in fruit size and peel thickness attributable to location, whereas rootstock had no significant effect on either fruit size or peel thickness. There were no correlations among fruit size, fruit quality, and peel thickness with Ca and P concentrations. However, there was a correlation between fruit size and peel thickness with K concentrations in the juice and fruit peel. Reduced peel thickness due to reduced K nutrition could lead to increased splitting of fruit. Therefore, the use of annual leaf samples to modify K fertilizer practices on a block specific basis should be implemented.


citrus sinensis; flatwoods; potassium nutrition

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283