A simple technique adapted to trap numerous air bubbles in agar deeps during their preparation was found to help nodulation of chickpea, soybean and other large-seeded legumes. Nodulation was consistently high in tubes of various sizes. Nodulation of chickpea and of soybean occurred at 2-4% agar and 0.75-2% agar concentration, respectively. The technique enhanced the precision of plant infection tests for enumerating
chickpea rhizobia in soils. Nitrogen fixing (C2H2) activities of nodulated soybean plants could also be determined.