Influence by artificial defoliation and NPK fertilizer application on growth and yield of Okra (<i>Abelmoschus esculentus</i> (L) Moench)

Abstract

A field trial to determine the effect of artificial defoliation and NPK fertilizer application on growth and yield of okra was conducted in 2010 and 2011 at the Teaching and Research Farms of the Faculty of Agriculture, University of Benin, Benin City, Nigeria. Okra “Uselu Local” was sourced locally and subjected to four rates of NPK fertilizer (0, 200 (30 kg N, 13 kg P and 30 kg K ha^-1); 400 (60 kg N, 26 kg P, 50 kg K ha^-1), and 600 (90 kg N, 60 kg P, 90 kg K ha^-1) kg ha^-1) at different percentages (0, 25 and 50 %) of defoliation respectively at four and six weeks after sowing. The experiment was laid out as a randomized complete block design arranged in a split-split plot and replicated three times. Each replication was allocated 12 treatments with NPK fertilizer application as the main plot, defoliation (sub-plot) and time of defoliation (sub- sub plot). Data were collected on parameters such as days to 50 % flowering, plant height at which fresh pods were harvested, plant height at which dry pods were harvested, number of pods per stand, average pod weight, pod weight per stand, pod yield per hectare, pod diameter, number of dry pod per stand, number of seeds per pod and stand. Obtained data were analyzed using analysis of variance procedure for split – split plot design and means were compared using LSD at 5 % level of significance. Results obtained indicated that defoliation considerably affected plant height and days to 50 % flowering. The reduction in growth due to defoliation was observed to be significant at four weeks after sowing of okra. NPK fertilizer application significantly reduced the deleterious effects of defoliation with regards to plant heights, days to 50 % flowering and yield of okra. The NPK fertilizer application promoted vegetative growth to cushion the adverse effects of defoliation. The interaction between NPK fertilizer application and defoliation was only significant on number of seeds per pod. There were significant interactive effects between NPK fertilizer and time of defoliation on plant heights and number of seeds per pod. Increasing in NPK fertilizer application above 200 kg (30 kg N, 13 kg P and 30 kg K ha^-1) NPK fertilizer ha^-1 could be profitable and to bring about a considerable increase in the growth and yield of okra.

Keywords: Defoliation, NPK fertilizer, okra, yield