IMPACT OF NITROGEN ON VEGETATIVE GROWTH OF MATURE PEACH TREES IN A SUBTROPICAL CLIMATE

Abstract

The current Florida peach industry is predominantly located in a subtropical climate, and fertilization regimes developed in temperate climates may not fulfill the nutritional demand for extended postharvest vegetative growth. The objective of this research was to determine the optimal rate of nitrogen fertilizer for mature trees in a subtropical environment. Four rates of nitrogen (N) plus a control (0 kg ha-1 of N) were applied to six-year-old ‘TropicBeauty’ A— ‘Flordaguard’ and included: 45, 90, 179, and 269 kg ha-1 of N applied annually during the 2011 and 2012 growing season. Vegetative growth measurements included trunk cross-sectional area (TCSA), vegetative and floral bud distribution on 1-year-old growth, pruning weights, total leaf N content and chlorophyll content. TCSA and pruning weights were not statistically different; however, trees with 0, 45, and 90 kg ha-1 of N tended to be smaller than those receiving 179 and 269 kg ha-1 of N annually. Vegetative and floral buds were fewer in trees receiving the low N rates (0 and 45 kg ha-1 of N) with high numbers of blind nodes in all treatments. Leaf N concentration was lower in the 0 and 45 kg ha-1 of N treatments (3.7%) than the highest two N treatments (4.1%). Although trees in the lowest N treatments contained seemingly adequate leaf N concentration, decreasing vegetative and floral buds over subsequent years may lead to smaller trees with reduced yield, while trees with higher rates of N produced larger canopies, requiring more severe pruning to maintain productivity.