Nodulation, growth and yield response of soybean [(Glycine max l. (merril)] to inoculum (Bradyrhizobium japonicum) under phosphorus levels and compost amendment in Northern Ghana

Abstract

The need for the use of fertilizers in soybean cultivation is inevitable in soils inherently low in soil fertility status. This experiment was conducted at Cheshegu in the Northern region of Ghana (2011 planting season) to determine the effectiveness of Bradyrhizobium japonicum (INO) on soybean, under four levels of phosphorus (0, 30, 60 and 90 kg P2O5 ha-1) and two levels of compost (0 and 3 tons ha-1). The experimental layout was randomized complete block design arranged in split-plot and replicated four times. The main plot is B. japonium (+ and -) and the combinations of compost and phosphorus levels were the split plots, parameters measured were; number of nodule plant-1 , nodule dry weight kg ha-1, biomass yield kg ha-1, pod number plant-1, pod weight kg ha-1, grain yield kg ha-1 and hundred seed weight. The results obtained indicated significant (P < 0.05) nodule dry weight with the use of sole compost (COM) and B. japonium+compost. Biomass yield was significantly enhanced with the use of sole compost and compost+P2O5–levels with and without inoculum, with the absolute control having the lowest value in all. Also, the application of 30 kg P2O5 ha-1+ B. japonium and 30 kg P2O5 ha-1+COM led to the highest pod number. Treated plots with and without B. japonium recorded significant (P < 0.05) pod weight and grain yield which were not less than 55 and 26% increase over the control plots, respectively. This study concludes that the use of compost combined with inorganic fertilizer (30 kg P2O5 ha-1) and/or B. japonicum inoculum enhances soybean nodulation, growth and yield in the study area.