Asian Journal of Research and Review in Agriculture

The deficiency of N in the dwarf coconut palm causes a drop in production, requiring replacement. The objective of the work was to evaluate the effect of different concentrations of the urea solution applied to the leaf axils of the green dwarf coconut tree and also to evaluate the use of the chlorophyll meter to estimate the levels of N associated with the hidden deficiency of this element. The concentrations of 0; 30; 60; 90; 120; 180 and 240 g L-1 of urea were applied to the axillae of leaves 8 and 9 of the coconut tree (100 mL in each leaf) at 0, 60, 120, 180, and 240 days. Leaf analyzes of N were performed at 180 and 255 days after the start of applications. At 255 days, 20 central leaflets were collected between leaves 9 and 14 (total of 70 samples) and seven intensities of green color, ranging from intense green to yellow, were selected. The leaflets were subjected to the reading of the chlorophyll meter (SPAD-502) and analyzed for the concentration of chlorophyll, carotenoids and N. The results indicated that the critical N level of the leaves of the coconut tree was not reached with the urea concentrations. No phytotoxic effects were observed at the urea application site, but there was a reduction in the number of reproductive structures of the coconut tree in concentrations above 125 g L-1. Chlorophyll meter readings between 41 and 72.8 indicate that the N content is below the critical level and the chlorophyll meter can be indicated to diagnose hidden deficiency.