Effects of glyphosate application and seed inoculation on the growth characteristics and yield performance of cowpea.

Abstract

Cowpea is an important food crop for the people living in the sub-Saharan regions of Africa given its adaptation to the ecological conditions. Its production is hampered by soil infertility and weed infestation. Thus, this study investigated effects of glyphosate application and seed inoculation on the growth characteristics and yield performance of cowpea. The experimental design was an RCBD with the treatments being inoculum and glyphosate. Data was collected on the growth parameters; number of root nodules, number of leaves, tap root length, number of branches, plant fresh weight, and stem height, and yield parameters; number of pods, weight per pod, weight of 100 seed, yield per hectare. The average number of root nodules in plots treated inoculum and those of the control plots have no significant difference (p<0.05) but are significantly different from plots treated with glyphosate and those treated with both glyphosate and inoculum. The herbicide had a significant (p<0.05) effect on the number of branches with inoculum treatment having the highest (8.7) and glyphosate plus inoculum as the lowest. (5). There wasn’t any significant (p<0.05) difference in the weight of the shoots in all the treatments. Treatment with glyphosate had a negative effect on the number of leaves with lowest plot being glyphosate treated (48.3) and the highest being inoculum treated (110.7). There was no significant difference in the stem length and tap root length when glyphosate and inoculum was applied. There was no significant difference in number of seeds of pods when treated with glyphosate and inoculum. Glyphosate had a significantly (p<0.05) negative effect on the number of pods per plant with highest from control (16) and lowest from the glyphosate treatment (11.3). Average number of pods, weight of 100 seeds and yield per hectare were negatively affected by glyphosate application but positively affected by inoculum application. The application of glyphosate herbicide as means of weed control has a significant negative effect on the growth and yield characteristics of cowpea. It the reduced level of colonization and activity of the nitrogen fixing bacteria as shown by fewer nodulation in glyphosate treated may also be attribute to physiological effects of the herbicide contrary to inoculum. Inoculum should be used to boost yield and glyphosate avoided till further research is carried on the best use procedures in cowpea.