The Impacts of Climatic Variability on the Grain Yield Performance of Open Pollinated Varieties (OPV) of Maize in a Rainforest Location of Nigeria

Aims: The objectives of the study were to examine the effects of climatic factors on maize yield and identify best planting date for maize in Rainforest Agroecology of Nigeria.

Study Design: Grain yield of seventeen open pollinated varieties of maize evaluated in 21 randomly selected environments in the Rainforest Agroecology of Nigeria were used for the study. Each field experiment was laid out in a randomized complete block design with four replications and 5 m long single-row plots spaced at 0.75 m apart and three seeds were planted 0.5 m apart within the row.

Place and Duration of Study: Grain yield of 17 maize varieties evaluated at the Obafemi Awolowo University Teaching and Research Farm (7°28'N, 4°33'E, altitude 224 m above sea level) during the late cropping seasons of 2001, 2005 and early cropping seasons of 2002, 2006 were used for this study.

Methodology: The grain yield and climatic data within the period of evaluation was subjected to Analysis of variance and correlation analysis.

Results: Rainfall alone significantly accounted for over 42 % of the total variation on grain yield across the environments while the combination of two climatic factors revealed significant variation across the combination ranging from over 41 % to 45 % with minimum relative humidity and maximum temperature together having the highest significant variation on grain yield of Maize. There was also highly significant positive correlation between grain yield and total rainfall (r = 0.65**) and minimum relative humidity (r = 0.64**).

Conclusion: Ranking of the twenty-one environments for average grain yield, the most favourable planting date ranged from early April to early May in Rainforest Agro-ecology of Nigeria.