Nodulation and Nitrogen Fixation in Soybean (Glycine max (L.) Merrill) As Influenced By Rhizobium Seed Inoculation with Different Adhesives in a Sandy Clay Loam Soil.

Abstract The study evaluated the efficacy of different adhesives added to rhizobial seed inoculum on soybean growth, nodulation and biological nitrogen fixation in a screen house and under field conditions. The experiment was a 6 × 3 factorial arranged in Completely Randomized Design and Randomized Complete Block Design for the screen house and field trial, respectively, with 3 replications. The adhesives were mixed with Bradyrhizobium japonicum (Rhizo-fix®) at three ratios: 1: 1, 1: 2 and 1: 3 (inoculants: adhesive). The effectiveness of adhesives in terms of the amount of viable rhizobial cells that adhered to coated seeds was determined using plate count technique from serially diluted 10-4 CFU. Nitrogen fixed (NF) was determined at R2 stage using Ureide method. The CFU/g of soil rhizobial cells was determined at 8 weeks after planting (WAP) using the same plate count technique. The result obtained indicated that gelatin (G) had the most viable rhizobial cells on seeds (CFU/seed). It had 88 %, 87 % and 84 % significant increment in cfu/seed when compared with cassava starch (CSV), corn starch (CS) and gum arabic (GA), respectively. However, CSV and CS treated plants had more N fixed than G; the N fixed was positively correlated with nodule fresh weight. Mixing ratios had no effect on most parameters measured except on soil B. japonicum population and no. of leaves at 8 WAP. Hence, the least ratio (1:1) which is probably the most economical should be adopted for rhizobial inoculation. Generally, results obtained by locally sourced adhesives averagely equaled those obtained by the conventional adhesives that had better adhering capability. It is therefore concluded that locally sourced adhesives such as cassava starch and corn starch could be suitable alternatives to conventional adhesives which is often more expensive and not readily available. Keywords: Adhesives, Inoculation, Bradyrhizobium japonicum, Nitrogen fixed.