Yield response of cowpea varieties to sowing dates in a Sudan savannah agroecology of Nigeria

Abstract

In the Sudan savannah of Nigeria, sowing date of cowpea is an important production constraint due to erratic rainfall at the beginning and towards the end of the rainy season when temperatures are high. Field trials were conducted during the rainy seasons of 2009 and 2010 at Minjibir (lat 12^o 08’N, long 08^o 32’E, elevation 508 m above sea level) in Sudan savannah of Nigeria, to determine the appropriate date of sowing of some recently developed cowpea varieties. Split-plot design was used with three replications. Sowing dates (10 July, 17 July, 24 July and 31 July) were assigned to main-plots and cowpea varieties (IT98K-205, IT97K-499-35, IT98K-573-2-1, IT89KD-288 and IT99K-241-2) were assigned to sub-plots. The results showed significant differences among cowpea varieties for yield and yield components. Sowing date significantly affected the performance of the five-cowpea varieties. Interaction between sowing date and variety was not significant for grain yield, suggesting that the varieties responded similarly to sowing date. Cowpea sown on 31 July produced significantly higher number of pods, number of seeds and grain yield compared with other sowing dates. Increase in grain yield for a sowing date relative to 10 July sowing was 26, 77 and 106% for 17, 24 and 31 July sowing, respectively. The medium maturing variety IT98K-573-2-1 significantly produced the highest number of pods, number of seeds and grain yield at all sowing dates. Based on these findings, for obtaining optimum yield, cowpea varieties should be sown at the end of July while for maximum yield, medium maturing cowpea varieties such as IT98K-573-2-1 are recommended.

Key words: Vigna unguiculata; grain yield; fodder yield; Sudan savannah