RESPONSE OF RAPID DECLINE AFFECTED COCONUT (COCOS NUCIFERA L.) PALMS TO MICRO-NUTRIENTS AND COMMON SALT

Coconut Rapid Decline (CRD) is a serious disorder of coconut palms (Cocos nucifera L.) in Sri Lanka. A substantial loss of crop is well evident due to this disorder. This study aims to determine the effect of micronutrients and common salt on the performance of CRD-affected palms. Fifteen-years-old, mild, moderate and severe CRD-affected palms, in Makandura Research Station (MRS) of Coconut Research Institute were used for this study. Affected palms were treated with the micro-nutrients (100 ml of 0.35 % CuS04.5H2 0 and 0.72 % ZnS04.7H2 0 solution/palm, root feeding at bi-monthly intervals) or common salt (NaCI, 1 kg/palm/year, surface application in the manure circle). Untreated CRD-affected palms were used as the control. Leaf nutrient levels before, one and two years after treatment application were analyzed. Vegetative, reproductive and physiological parameters were measured during two years, after treatment application. Pre-treatment analysis of leaves revealed that Nitrogen (N) and Phosphorus (P) contents were within the sufficiency range and Potassium (K) content was above the sufficiency range in CRD-affected palms. Magnesium (Mg), Calcium (Ca), Sodium (Na), Copper (Cu) and Zinc (Zn) contents of those palms were below the sufficiency range. The macro and micro-nutrient contents (except Mg) of apparently healthy palms, adjacent to CRD-affected palms were within the sufficiency range for coconut. Therefore, it is suggested that the CRD-affected palms suffer from deficiency of Ca, Na, Cu and Zn. There was a significant difference in Iron (Fe) content among three severity stages of CRD-affected palms before initial treatment application, Fe concentration increased with increasing severity. Phosphorus and Ca contents significantly increased in micro nutrient and common salt treated palms after one year, compared to before treatment application and control. However, there was no significant increase in leaf Cu, Zn and Na levels, even after two years of the treatment application. The percentage of drooping fronds, size of the spadix, number of female flowers, number and size of nuts and circumference of the trunk were not improved in treated palms one year after treatment. Two years after the treatment, number of total fronds and functional green fronds in the canopy of affected palms were increased by common salt application. The stomatal diffusive resistance of these palms was also reduced after two years showing an improvement in palm water status. The experiment is in progress to. observe the recovery of symptoms