Nitrogen fixation and nodulation of soybean as affected by rhizobial inoculation using different seed adhesives in a sandy clay loam soil.

Abstract

The study evaluated the efficacy of different adhesives added to rhizobial seed inoculum on soybean 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 pot and field trials, respectively, with 3 replications. Cassava starch (CSV), corn starch (CS), honey (H), gelatine (G), gum arabic (GA) and water (W) were mixed with Rhizo-fix® at three ratios: 1: 1, 1:2 and 1:3 (inoculants: adhesive).Viable rhizobial cells on coated seeds were determined using plate count technique from serially diluted 10-4 aliquot. Nitrogen fixation (NF) was determined using ureide method. Gelatine had most rhizobial cells on seeds (CFU/seed). It had 88, 87 and 84% significant increment when compared with CSV, corn starch CS and GA, respectively. However, CSV and CS considerably had more N fixed than G and was positively correlated with nodule fresh weight. Mixing ratios had no effect on parameters observed. Generally, results obtained by locally sourced adhesives averagely equalled those obtained by the conventional adhesives that had better adhering capability. Thus, locally sourced adhesives could be an alternative to conventional adhesives which are often more expensive and not readily available. Moreover, since mixing ratio had no significant effect on most parameters measured, then the least ratio (1:1) which is probably the most economical should be adopted for rhizobial inoculation.

Keywords: adhesives, inoculation, Bradyrhizobium japonicum, nitrogen fixation