Effects of Rates of NPK, Neem-Based Organic Fertilizer and their Combinations on Okra (Abelmoschus esculentus L. Moench) Yield and Leaf Nutrient Content in South-eastern Nigeria

Herein, the effect of applying different rates of inorganic fertilizer (NPK 20:10:10) and organic fertilizer (neem seed) and their combinations on plant nutrient concentration and yield of okra was studied under field conditions at two locations within the University of Calabar Teaching and Research Farm. The experiment was laid out in a randomized complete block design with three replications. Eleven treatments were applied. These were comprised of a control (no amendment), sole NPK 20:10:10 fertilizer and neem–based organic fertilizer applied at two rates (100 and 120 kg N/ha), combinations of 60 kg N/ha NPK+ 60 kg N/ha Neem, 50 kg N/ha NPK+ 50 kg N/ha Neem, 90 kg N/ha NPK + 30 kg N/ha Neem,25 kg N/ha NPK+ 75 kg N/ha Neem, 30 kg N/ha NPK + 90 kg N/ha Neem and 25 kg N/ha NPK+ 75 kg N/ha Neem. Amongst the two rates (100 and 120 kg N/ha) of sole application of either NPK or Neem-based organic fertilizer, the 120 kg N/ha recorded the highest number of fruits set and okra fresh fruit yield. The combination of 60 NPK + 60 Neem kg N/ha increased the yield (8.43 t/ha) and yield components of okra, while the 90 NPK + 30 Neem kg N/ha and 30 NPK + 90 Neem kg N/ha increased nutrient concentration in the okra plant. Thus, for sole application, the 120 kg N/ha application of either nutrient source is appropriate, but for optimum yield of okra in the tropical rainforest zone of Nigeria, the combination of both organic and inorganic fertilizer especially at 60 kg N/ha of each nutrient source, is recommended.