Boron Deficiency In Young Coconut (Cocos nucifera L.) In Sri Lanka Symptoms and Corrective Measures

Apart from N, P, K, and Mg deficiencies in coconut so far observed in Sri Lanka, boron (B) deficiency was observed in 12 young coconut palms of age 1-3 y at Poojapitiya in Kandy district. The symptoms were : Unsplit, crinkled nature of leaflets; stunted and withered apical leaves; lack of leaflets in some fronds. The third leaf of the affected palms had 3.4—7.5 ppm B as compared to 7.6—10.0 ppm B for healthy palms in the same vicinity. Soil application of sodium tetraborate (Na2B04 . 5H20) at the rate of 28 and 56 g/palm to the affected palms at incipient stages improved the condition of palms within six months and complete recovery was achieved at the end of eight months. However, the symptoms in the untreated affected palms gradually became acute and the palms died after 6-8 months. Results suggest that the critical nutrient concentration range for B in the third leaf is 8-10 ppm and the deficiency could be corrected only at the incipient stages by soil application of sodium tetraborate. doi: 10.4038/cocos.v6i1.2053 COCOS 1988 Vol.6 No.1 31-3