Journal of Experimental Agriculture International

Aims: This research was conducted in pot of trials at the farm land of Lawra-Yagtuuri in the Upper West Region to determine the effect of Rhizobia inoculants, Boostxtra, and appropriate Phosphorus Fertilizer level required for cowpea growth and yield.

Study Design:  The research design used in this study was experimental. Specifically, the experiment was run as a split-plot design.

Place and Duration of Study: Department of Statistics and Department of Mathematics, University for Development Studies, between November, 2015 and July, 2016.

Methodology:   The experiment assessed the effects of rhizobia inoculants at two levels (2.5 g and 5.0 g) per kg, boostxtra and four levels of phosphorus fertilizer (0 kg P₂O₅ ha^-1, 25 kg P₂O₅ ha^-1, 50 kg P₂O₅ ha^-1and 75 kg P₂O₅ ha^-1) on the growth and yield of cowpea. It was run in a split-plot design. The analysis was done using Generalized Linear Model and Subset Regression.

Results: Phosphorus Fertilizer and Boostxtra significantly enhanced cowpea growth and yield; Pod weight plant (g), Nodule dry weight (g), Pod and Nodule numbers in all the weeks of measurement were significantly improved. However, the highest yield was observed at 50 kg P₂O₅ ha^-1. Cowpea response to rhizobia inoculation was not sufficient to raise cowpea yield. The model was significant (P<0.05) accounting for 77.70% of total variation in the yield. The subset regression analysis had C(p)=5.28 from six variables in the model with the Adjusted R Square = 0.9318.

Conclusion: The ability to optimize cowpea grain yield depends on the application of 50 kg P₂O₅/ha and Boostxtra and care should be taken to apply the right amount of Phosphorus Fertilizer.