Response of Okra to Incorporating Humic Acid-Derived Active Molecules into NPK Fertilizer and Lime on Coastal Plain Sand in Calabar, Nigeria

This study evaluated the response of okra to NPK fertilizer with humic acid and lime at the University of Calabar, Teaching and Research Farm between October 2015 and January 2016 cropping season. The experiment was laid out in a randomized complete block design (RCBD) with four replications. The experiment consisted of NPK with humic acid and liming materials as treatments. The test crop was okra. The result of initial analysis of the chemical properties of the soil before the experiment showed that the soil was acidic and was low in exchangeable bases, organic matter (1.13%), total nitrogen (0.14%) and ECEC but high in available phosphorus (26.63 mg/kg) and base saturation. After application of treatment, the result showed that 6.2 g of lime and 4.6 g of NPK with humic acid increase the soil pH from 5.6 units in the control to 5.8 in NPK with Humic Acid, 6.0 in NPK with Humic Acid and lime and 6.4 in lime. Organic carbon content, total nitrogen and available phosphorus also increase in like manner. The results for the growth parameters showed that okra height, number of leaves, and pod yield were significantly (p≤0.05) different from the control. Based on the result of this study further research is recommended in other locations to fully ascertain the effects of this treatment using a different combination.