Abstract

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There is a dire need to determine the most critical time of fertilizer application when demand for nutrients is highest in the growth cycle of crops in order to achieve the objective of increased crop yield, associated with fertilization. Consequent upon this, a two – year field experiment was carried out at the Teaching and Research Farm of the Ekiti State University, Ado – Ekiti, Ekiti State, Nigeria, during 2013 and 2014 cropping seasons to determine the effects of timing of NPK fertilizer application on the yield and yield parameters of okra (Abelmoschus esculentus) and soil fertility status. The experiment was laid out in a randomized complete block design with three replicates. The NPK fertilizer application regimes included: no fertilizer application (NFA), which served as control or check; application at 3, 6 and 9 weeks after planting (WAP). The results obtained indicated existence of significant (P = 0.05) differences among the NPK fertilizer application regimes with respect to their effects on soil nutrient status and okra growth and fruit yield. At the end of 2013 cropping season, NPK fertilizer application regimes resulted in significant increases in soil organic carbon (SOC) from 0.21 g kg^-1 for NFA to 0.30, 0.41 and 0.50 g kg^-1 for application at 3, 6, and 9 WAP. Similarly, at the end of 2014 cropping season, NPK fertilizer application regimes resulted in significant increases in SOC from 0.16 g kg^-1 for NFA to 0.24, 0.35 and 0.42 g kg-1 for application at 3, 6, and 9 WAP. At the end of 2013 cropping season, NPK fertilizer application regimes resulted in significant increases in total N from 0.20 g kg^-1 for NFA to 0.19, 0.25 and 0.33 g kg^-1 for application at 3, 6, and 9 WAP. At the end of 2014 cropping season, NPK fertilizer application regimes resulted in significant increases in total N from 0.10 g kg^-1 for NFA to 0.15, 0.22 and 0.28 g kg^-1 for application at 3, 6, and 9 WAP. Mean values of okra fruit yield data across the two years of experimentation indicated that, NPK fertilizer application regimes significantly increased okra fruit yield from 0.37 t ha^-1 for NFA to 1.15, 1.02 and 0.83 t ha^-1 for the respective application at 3, 6 and 9 WAP.

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