Effect of plant population density on growth and yield of sunflower (Helianthus annum L.) in the transition zone of south west Nigeria.

Abstract

Experiments were conducted in south west Nigeria to evaluate the response of sunflower {Helianthus annuus L.) to different plant population densities under rain fed conditions during the late rainy season cropping o f 2002 and 2003. In both years, three open pollinated varieties namely: Funtua ( a local adapted variety), Record and Isaanka (exotic varieties) were grown at three spacings, 60 x 15,60 x 30 and 60 x 45cm, to achieve 37,500,55,000 and 111,000 plants/ha, respectively. Funtua flowered and matured later and grew taller than Record and Isaanka in 2002 and 2003. Similarly, Funtua significantly out-yielded Record and Isaanka in both years. Increase in population density significantly reduced stem girth and increased lodging in 2003. As population density increased from the lowest (37,500 plants/ha) to the highest (111,000 plants /ha), seed production efficiency significantly increased, whilst average head diameter, head weight, achene weight/head, number o f achene/head and 100 seed weight significantly reduced in 2002 and 2003, respectively. The highest plant population density produced significantly higher seed yield than the intermediate (55,000 plants/ha) and the lowest by about 37 and 64%, and 75 and 98% in 2002 and 2003, respectively. The overall yield response was highest at 111,000 plants/ha irrespective of variety in both years. It is therefore, concluded that sunflower could be grown up to 111,000 plants/ha under rain fed conditions in the transition zone of south west Nigeria.