Growth and yield response of cowpea to rhizobium inoculation and phosphorus fertilizer application

Abstract

The field experiment was carried out at Makerere University Agricultural Research Institute, Kabanyolo (MUARIK) in Wakiso district, Uganda to evaluate the growth and yield response of cowpea to rhizobium inoculation and phosphorus fertilizer application in a randomised complete block design with split plot arrangement, and replicated three times. The main plot treatments comprised the inoculation with cowpea rhizobium, while the sub-plots comprised four levels of phosphorus (TSP) fertilizer application. The fertilizer treatment levels were: 0 kg P/ha (the control), 20kg P/ha, 40kg P/ha and 60 kg P/ha. The data collected included; dry weight of aboveground biomass, dry weight of belowground biomass, number of leaves per plant, number of nodules per plant, number of pods per plant, number of seeds per plant, weight of 100-grains per plot and grain yield per square metre. Results from the experiment showed that rhizobium inoculation and application of phosphorus fertilizer better enhanced growth characteristics and nodulation of cowpea when compared with the un-inoculated cowpea seeds. The un-inoculated cowpea seeds gave higher grain yield than the inoculated ones. The 40 kg P/ha application rate recorded the highest grain yield than all the other P fertilizer levels. It was, therefore, recommended that rhizobium inoculation with P fertilizer application rate of 40 kg P/ha should be used for vegetative growth while as P fertilizer application only should be used for grain production.