The 2012 ASHS Annual Conference

Subtropical peach production in Florida is increasing as growers seek to diversify their farms to spread financial risk.  Growers in Florida have taken advantage of an unique marketing window (April–May) to be the first domestic supplier of peaches to consumers.  Many growers have had to adapt nitrogen fertilizer recommendations from temperate or Mediterranean climates to that of a subtropical climate and may be over- or under-fertilizing trees. An initial grower survey indicated that annual nitrogen application rates range from 112 to 224 kg/ha.  At least two commonly grown commercial peach varieties produce large numbers of blind nodes, often exacerbated by high nitrogen applications and warm temperatures. In addition, high nitrogen rates have previously been shown to increase vegetative growth, leading to increased shading and decreased fruit quality.  The narrow marketing window requires that subtropical peach producers optimize production methods to ensure high quality fruit. This research was initiated to examine four different rates of nitrogen (44.8, 89.6, 179.3, and 269 kg/ha) in addition to a control (0 kg/ha) to examine the impact on vegetative growth, leaf nitrogen content, and bud distribution in mature ‘TropicBeauty’ peach trees. Phosphorus and potassium were applied separately to all trees at an annual rate of  33.6 kg/ha, in addition to foliar micronutrient sprays throughout the season.  The experiment was set up using a completely randomized design with single tree replicates (N=6).  Vegetative growth was collected using annual pruning weights, while bud distribution (live/dead flower, live/dead vegetative buds, and blind nodes) was collected from one-year old branches.  Imposition of nitrogen rate treatments resulted in significant alterations in bud distribution, with an overall reduction in blind nodes (44 nodes/branch to 19 nodes/branch).  Flower buds were greatest (9.9 buds/branch) in the highest nitrogen rate treatment (269 kg/ha), while vegetative buds were the greatest in the control (4.3 buds/branch) and in the highest nitrogen rate. Increased vegetative buds did not translate to significantly higher pruning weights; however an increasing trend was observed with the highest N rate.  Despite increased numbers of flower and vegetative buds in the control (0 kg/ha), leaf nitrogen rates reflected excessive concentrations (4.3%), leading to the possibility that growers in subtropical climates may be over fertilizing.

Abstracts:

• Total Leaf N.jpg (99.2KB) - Abstract Text