Field experiments were conducted at Teaching and Research farm of Landmark University in 2012 and 2013 to investigate the influence of three population densities (88,000, 44,000, and 29,000 plants/ha) on the growth and yield of five cowpea varieties (IT97K-461, IT97K-568-18, IT98K-131-2, IT99K-1060 and IT99K-`245). Plant growth parameters such as plant height, and number of trifoliate leaves per plant and flower production dynamics at harvest the following parameters were measured; pods yield per plot, seed per pod and grain yield. Results showed that there were no constant trends in growth parameters response to population density in both years. Plant height and flower production increased with increased population density. Also, number of leaves per plant and dry matter increased with increasing population density. All these parameters were significantly affected with variety, while there was no significant interaction effect. Most yield components increased with increasing population density as well as grain yield which increased with increasing population density. All yield parameter and grain yield significantly varied with variety, while there was no appreciable interaction effect. In conclusion, a population density of 88,000 plants ha-1 gave the highest growth and grain yield. Therefore, genetic improvement of cowpea varieties can be enhanced by selection at higher population densities.

Keywords: comparative, growth, Vigna unguiculata, population density, grain yield