Evaluation of Liming Materials and Bradyrhizobium Inoculation on the Productivity of Soya Bean in the Humid Tropical Ultisols of Southeastern Nigeria

Abstract: Field experiments were conducted in 2009 and 2010 to evaluate the response of soya bean to pre-sowing seed inoculation with Rhizobium japonicum strains and liming the soil with different lime materials. The experiments were conducted on sandy loam soils at Calabar in the rainforest and Obubra in the southern guinea savanna zones of Cross River State, Nigeria. Treatments comprised factorial combinations of Rhizobium (with and without inoculation) and liming material (no lime, calcite, gypsum, and dolomite) laid in randomized complete block design replicated thrice. Liming the soil was effective in increasing root nodulation, plant vegetative growth and grain yield in Calabar, but not at Obubra. Pre-sowing seed treatment with Rhizobium japonicum was also more effective in Calabar than at Obubra. Root nodulation, plant height, pod-bearing branches, reproductive node number, dry matter yield, pods/plant and yield of grain were significantly influenced by the combined effect of inoculation and liming, but not the number of seeds and seed weight/pod.  Sowing inoculated seeds in calcite- limed soils gave the best results but the difference between gypsum and dolomitic lime was not significant. The grain yield which averaged 2.34 t/ha in the Obubra grown crop was higher by 21.9 % compared to the Calabar grown crop. Differences in the response to seed inoculation and liming were attributed to weather and edaphic factors.