Irrigation Scheduling, Nutrient Application Frequency, and Freezing Acclimation of `Hamlin' Orange Trees in Florida

Abstract

`Hamlin' orange trees [C. sinensis (L.) Osb.] from a commercial nursery were planted into raised beds on a site that simulated conditions typical of the flatwoods region of the citrus industry. A factorial experiment with three irrigation schedules, based on growth flushes and three nutrient application frequencies (total N, 0.136 kg/tree per year), was conducted in 1994. Trees were irrigated using 90° microsprinklers, and soil moisture content was monitored using a neutron probe. Eleven replicate trees of the nine treatments were included in a completely randomized block design. Weekly freeze tests using the electrolyte leakage method were conducted at –4, –6, and –8C. Electrolyte leakage was determined using a conductivity meter. Different irrigation scheduling based on growth flushes had no significant effect on freezing acclimation. However, increased frequency and lower amounts of fertilizer per application significantly (P = 0.05) increased freeze hardiness from 4.2 to –6.10C by the end of November. Morphological data including trunk diameter, tree height, and flushing status also were recorded. Increasing frequency of nutrient application resulted in a more rapid acclimation of young `Hamlin' orange trees.