Efficacy of Foliar Urea as an N Source in Sustainable Citrus Production Systems
Foliar fertilisation was reported to be an efficient way to supply nitrogen to fruit trees and to reduce nitrogen losses to groundwater systems and risks of soil pollution and salinity. In this study we report on: 1) the effect of pH of a 1% urea solution applied prebloom and the effect of a multiple foliar-urea spray at the rate of 1% to supply 46 g N/tree to mature ‘Cadoux’ clementine mandarin trees (Citrus reticulata Blanco) on leaf N and its changes during 30 days following application; 2) the resulting effect on yield and fruit size; 3) a comparison made between effects of prebloom foliar application of urea at 0.8% or 1.6% (supplying 37 and 74 g N/tree, respectively) with prebloom soil applications of ammonium nitrate supplying 75 or 150 g N/tree on fruit size, fruit set and total yield. Results indicate that foliar urea increased leaf N content during the first 48 hours following treatment regardless of pH.