Response of high yielding coconut variety and hybrids to fertilization under rainfed and irrigated conditions

A long-term experiment was conducted to study the differential fertilizer response of high yielding West Coast Tall variety, Chowghat Orange Dwarf (COD) × West Coast Tall (WCT) and WCT × COD hybrids of coconut for growth, nutrition, yield and economic returns under rainfed and irrigated conditions at Central Plantation Crops Research Institute, Kasaragod. The average yield for 8 years showed that the fertilizer treatment 1000 g N: 437g P: 1667g K palm-1 yr-1 (M2) recorded significantly higher nut yield (136 nuts palm-1 yr-1) than M1 treatment (500 g N: 218 g P: 833 g K palm-1 yr-1) and no fertilizer application (M0). Amongst the variety/hybrids, the hybrid COD × WCT (128 nuts palm-1 yr-1) out yielded its reciprocal cross (114 nuts palm-1 yr-1) and WCT variety (115 nuts palm-1 yr-1). The growth parameters recorded did not show any significant difference in tree height and girth at base among the variety/hybrids. However, fertilizer application significantly increased the trunk height and girth at base. Annual application of fertilizers for a period of 32 years to coconut resulted in a marked increase in available phosphorus and potassium status in soil, but a marginal change in soil available nitrogen status was observed. Foliar contents of N remained below the critical levels of 1.8-2.0%. Phosphorus buildup in the soil due to fertilizers, did not reflect in the P contents of diagnostic leaf under both rainfed and irrigated conditions. Application of K fertilizer at M1 level maintained K content of leaves at 1.07% i.e. just above the critical level (0.8-1.0%), whereas application of K fertilizers at M2 level raised the leaf K content to 1.20%. The leaf nutrient contents did not vary much among variety/hybrids due to fertilizer application. The cost-benefit ratio was most favourable under fertilizer treatment M1. For every rupee (Rs) invested on manuring, the total net return was Rs 2.80 under M1 level and Rs 2.85 under M2 level of fertilizers.