Effects of Neem-Based Organic Fertilizer, NPK and Their Combinations on Soil Properties and Growth of Okra (Abelmoschus esculentus) in a Degraded Ultisol of Calabar, Nigeria

A field experiment was conducted at the University of Calabar Teaching and Research Farm to evaluate the effects of neem-based organic fertilizer, NPK and their combinations on soil chemical properties and growth of okra (Abelmoschus esculentus) on a degraded Ultisol Calabar. The experiment was laid out in a randomized complete block design with three replications comprising of six treatments. The treatments were control (no amendment), sole NPK 20:10:10 fertilizer and neem–based organic fertilizer applied at 120 kg N/ha, combinations of 60 kg N/ha NPK+ 60 kg N/ha Neem, 90 kg N/ha NPK + 30 kg N/ha Neem and 30 kg N/ha NPK + 90 kg N/ha Neem. Results showed that the soil chemical properties were influenced significantly (P<0.05) by the treatments with the highest pH and exchangeable Ca values obtained in plots treated with half NPK and half Neem while plots treated with sole Neem recorded highest values for CEC and base saturation. Soils treated with 60 kg N/ha NPK+ 60 kg N/ha Neem gave a significant (P<0.05) increase in plant height, number of leaves and stem girth at 4, 6 and 8 weeks after planting. Based on the results obtained, it can be inferred that the soils amended with 60 kg N/ha NPK + 60 kg N/ha Neem significantly (P< 0.05) increased the growth of okra in the study area and is therefore recommended.