The coconut palm or Cocos nucifera is a species of palm extensively cultivated in tropical climates. Nutrient content of market available compound fertilizers for coconut available in Sri Lanka are determined in the study. The fertilizers applied for coconut palms are of many types as chemical, mineral and organic fertilizers and there are fertilizer mixtures with known ratios and compound fertilizers with particular ratios. In this study N:P:K + MgO ratios of compound inorganic fertilizers for coconut palms available in the market are discussed. Nitrogen, Phosphorus, Potassium and Magnesium are essential macronutrients. Therefore, a fertilizer with the correct N:P:K ratio must be used for coconut. The amount of fertilizer that is needed for coconut trees differ from palm type and the zone the coconut trees are grown. Therefore, as a solution for that, Coconut Research Institute has introduced Fertilizer recommendations based on N, P, K and Magnesium requirement. In this study 20 fertilizer samples were collected from different distribution centres and nutrient analysis was carried out for Nitrogen, Phosphorus, Potassium and Magnesium. Nitrogen content was determined using alloy and without using alloy and 5 samples out of 20 can be selected as mixed fertilizers and all the other samples are Ammoniacal and Nitrate based Nitrogen fertilizers. From the analysis of Phosphorus by the UV- VIS spectrophotometry, there were no significant deviations in the results obtained and the company mentioned value. Both Potassium and Magnesium analysis was done by Atomic Absorption Spectroscopy. The data obtained for Potassium and Magnesium in the laboratory did not show any significant deviation. From all the data obtained none of the fertilizers matched with the fertilizer recommendations of the Coconut Research Institute for adult palms and young palms in the Wet and Intermediate zone and Dry zone. The fertilizer recommendation for the coconut palms given by the Coconut Research Institute is shown in Table 1.

Table 1: Fertilizer Mixture Recommendations for young and adult palms in Wet and Intermediate zones and Dry zone (Coconut Research Institute of Sri Lanka, 2018)

Young Palms

Wet and intermediate zone (YPM – W)

Nitrogen (N) 11% , Phosphorus Pentoxide (P₂O₅) 16%, Potassium Oxide (K₂O) 14%

(11-16-14)

Dry zone (YPM-D)

Nitrogen (N) 13% , Phosphorus Pentoxide (P₂O₅) 15%, Potassium Oxide (K₂O) 20%

(13-15-20)

Adult Palms

Wet and intermediate zone (YPM – W)

Nitrogen (N) 11%, Phosphorus Pentoxide (P₂O₅) 8%, Potassium Oxide (K₂O) 29%

(11-8-29)

Dry zone (YPM-D)

Nitrogen (N) 13%, Phosphorus Pentoxide (P₂O₅) 7%, Potassium Oxide (K₂O) 34%

(13-7-34)

The fertilizer application rates were calculated by balancing the nutrient composition of the fertilizer and the nutrient composition of the CRI recommended fertilizer application rates for adult and young coconut palms. The initial balancing was based on Nitrogen and the deficit amounts of other essential nutrients are supplemented through straight fertilizers available in the market, which are recommended for coconut palms.

Key words: Fertilizer, Nutrients, Recommendations