Nitrogen Requirements of Low-chill Peaches in a Subtropical Environment

In the past five years there has been a rapid expansion of Florida peach acreage as citrus growers seek alternative options to maintain agricultural profitability.  However, evergreen citrus production practices, specifically fertilization, are not optimized for low-chill deciduous peach production or quality.  Early season harvest of fruit with short developmental periods result in long periods of excessive vegetative growth in the humid, subtropical climate.  Thus, this project sought to identify ideal nitrogen fertilization rates for newly established and mature peach orchards in Florida.  Five nitrogen rates (0, 45, 90, 179, and 269 kg N/ha) were applied to six-year-old mature ‘TropicBeauty’ trees grafted onto ‘Flordaguard’ rootstock.  In a separate experiment, identical fertilization rates were applied with different application methods (granular vs. fertigation) as a split-split-plot in a newly-established orchard with ‘TropicBeauty’ and ‘UFSharp’ grafted onto ‘Flordaguard’.  Vegetative measurements, yield, and fruit quality characteristics were measured from 2011-2014.  In mature orchards, few significant differences were observed in vegetative growth parameters.  Trees receiving the two lowest N rates tended to have smaller trunk cross-sectional area and fewer vegetative and floral buds, while large amounts of blind nodes were produced in all treatments.  In young orchards, trees receiving 0 or 45 kg N/ha were significantly smaller as indicated by pruning weights, but no difference was detected in bud distribution.   Leaf N (%) increased along a linear gradient with increased N rate in both mature and young orchards; however leaf concentrations were excessive in both orchards (>4.0%). Fruit from mature orchards showed no differences in fruit color, brix, pH or titratable acidity, despite having larger fruit when 269 kg N/ha was applied.  Consumer taste panels identified differences in appearance but not in flavor, texture, or overall liking.  In this study, varying the N rate in a newly established orchard reflected differences better than in an existing orchard; perhaps because of the buffering capacity of the tree to mobilize N reserves from larger storage organs in the tree which are undeveloped in younger plantings.