2003 Volume 9 Issue 1 Pages 7-12
The effects of variable seasonal rainfall, predicted supplementary irrigation, cultural practices (land-forms, tillage and weed management) and their interactions on the yields of maize and cowpea grown on the Vertisols in the Accra plains are examined. Based on long-term (27-years) seasonal daily rainfall data and the test crops maize and cowpea, transformation factors of 1.61 and 1.24 are obtained for the major and minor seasons, respectively. These are subsequently employed to obtain potential yields of the crops under supplementary irrigation. The potential yields of maize and cowpea given supplementary irrigation are significantly (p<0.00l) higher than those under rainfed conditions. Maize average yield under rainfed and supplementary irrigation conditions were 1.8 ton/ha and 2.9 ton/ha, respectively, and the average yields of cowpea are 0.33 ton/ha and 0.40 ton/ha, respectively. The effects of supplementary irrigation, cultural practices and the treatments interactions also give significantly (p<0.00l) higher yields of maize and cowpea than under rainfed conditions. In seasons with normal or above-average rainfall, camber beds are more productive than flat plots. However, when the seasonal rainfall is low, flat plots are more suitable than camber beds for crop production. The maximum maize and cowpea yields on tilled plots under irrigation are 4.0 ton/ha and 0.66 ton/ha, respectively. The best maize and cowpea yields as influenced by weed and water management are 5.2 ton/ha and 0.74 ton/ha, respectively.
