Title: Effect of different population densities and fertilizer rates on the performance of different maize varieties in two rain forest agro ecosystems of South West Nigeria
Abstract: The study aimed at identifying the influence of different plant population density and fertilizer rates on three different maize varieties, it was carried out in two cropping seasons (2007/2008 and 2008/2009) at Ibadan and Ikenne in South-western Nigeria. The experiment was a split-split-plot design with three replications. Maize variety (Swan 1-SR an open-pollinated, Obasuper a hybrid and Quality Protein Maize, an improved) was used as the main plot, the sub-plot comprised three plant population densities determined from spacing combinations which are 53,320 plants ha-1 (75 x 50cm), 88,880 plants ha-1 (90 x 25cm) and 106,640 plants ha-1 (75 x 25cm) while the sub-sub-plot was NPK 20:10:10 fertilizer (applied at 120, 150 and 180 kg N ha-1). The results showed that there were significant differences (P≤0.05) for plant height, stalk diameter, stalk lodging, maize cob weight, cob diameter, cob length and grain yield due to influence of different rates of fertilizer and plant population density at both locations. Irrespective of the rates of fertilizer applied, there were no significant differences for stalk diameter at Ibadan and Ikenne. Also, maize variety did not significantly affect (P≤0.05) maize growth performances. However, the results indicated that, the application of 180 kg N ha-1 gave the highest grain yield of 3.8 and 3.5 ha-1at Ibadan and Ikenne, respectively, which was not significantly different from the application of 150 kg N ha-1. Thus, the plant population density of 88,880 plants ha-1 gave the highest maize grain yield while the lowest yields were recorded for plant population density of 106,670 plants ha-1 at both locations. The hybrid maize (Obasuper) variety gave the highest maize grain yield. Key words: Plant population density, fertilizer rates, maize varieties, NPK fertilizer, south west.