Growth, Nodulation, and Yield Responses of Groundnut (Arachis hypogaea L.) as Influenced by Combined Application of Rhizobium Inoculant and Phosphorus in the Guinea Savanna Zone of Ghana

Groundnut yields obtained by farmers in northern Ghana are generally low due to low soil fertility resulting from continuous cropping coupled with low use of external inputs. There is therefore the need to use systems' internal resources such as biological nitrogen fixation efficiently to enhance crop production. This on-station experiment investigated nodulation and pod yield responses of three groundnut varieties, namely Obolo, Oboshie and Samnut 22 to inoculation with rhizobium inoculants of exotic strains, namely Bradyrhizobium yuanmingense (BR 3267) and USDA 3456 in combination with 0 kg P ha(-1), 15 kg P ha(-1) and 30 kg P ha(-1). Combined application of 30 kg P ha(-1) and BR 3267 increased the nodule numbers in Obolo, Oboshie and Samnut 22 by 144%, 188% and 56%, respectively compared to their uninoculated counterparts. Inoculation with BR 3267 produced the highest pod yield in all the three varieties with yields increasing from 13 to 40% over that of the uninoculated treatments, with BR 3267-inoculated Samnut 22 giving the highest yield of 2013 kg ha(-1). P fertilizer and rhizobium inoculant also had a significant interactive influence on the pod yield of groundnut. Combined application of 30 kg P ha(-1) and rhizobium inoculation increased the groundnut yield by 64 to 68%. The study observed a positive interaction between the rhizobium strains and P fertilizer.