possible that the two cultivars of long bean had produced different properties of substances from the exudation process as stated by SubbaRao (1995). The period of growth of 30 days after planting of yard long bean plants could presumably be the peak period for growth of rhizobial population and this period could have coincidentally happened during the rapid growth period of the yard long bean plants. However, it might be of better justification if rhizobial population had been determined at least one week interval after the sowing of yard long bean seeds to the test tubes, hence more details of rhizbial population could be intensively evaluated. Residual Rhizobium being retained from the soil where yard long bean plants have been used to grow from time to time had some significant value for the survival and availability of rhizobial population in soil environments. Luangchaisri (1995) confirmed this Rhizobium technology with his experiments on soybean crop plants.