Varietal Effect of Cowpea and Cow Dung Application Rates on the Productivity of Cocoyam/Cowpea Intercrop

The varietal effect of cowpea and cow dung application rates on the productivity of cocoyam/cowpea intercrop were investigated in 2012 and 2013 cropping seasons at National Horticultural Research Institute (NIHORT), Mbato sub-Station, Imo State, Nigeria. The experiment was a factorial arrangement in a randomized complete block design with three replications. The treatments were four levels (0, 10, 20 and 30 t/ha) of application of cow dung and two cowpea varieties of different growth habits (climbing Akidienu and erect IT97K-499-35) intercropped with cocoyam. The sole crops were included in other to access the productivity of the intercrop. Cocoyam growth and yield parameters assessed included plant height, leaf area index (LAI), number of corms, corm weight and corm yield while cowpea parameters evaluated were plant height, shoot and root dry weights, number of pods/plant, fresh pod weight, fresh pod yield, number of seeds/pod, 100 seeds weight and seed yield. Intercropping cocoyam with climbing Akidienu significantly (P < .05) increased cocoyam plant height but decreased significantly (P < .05) leaf area index (LAI) by 50% and corm yield by 44% on average. However, intercropping cocoyam with erect IT97K-499-35 had no significant effect on cocoyam plant height but significantly decreased LAI by 17% and corms yield by 23%. Fresh pod and seed yields were not affected by intercropping except in 2012 where fresh pod yield of erect IT97K-499-35 intercropped with cocoyam was significantly increased by 17% over the sole crop yield. Generally, erect IT97K-499-35 produced higher fresh pod and seed yields than climbing Akidienu in both cropping systems. Application of cow dung at 20 t/ha gave optimum corm yield while pod and seed yields of the cowpea varieties were improved by the lower rate of 10 t/ha. Cocoyam mixed with erect IT97K-499-35 produced the highest mean total LER of 2.53; LEC of 1.44 and ATER of 1.58 when cow dung was applied at 20 t/ha.