Effect of Inoculation Methods on Nodulation, N2 Fixation and Yield of Soybeans Under Field Condition

To benefit from N2 fixation soybeans have to be nodulated by rhizobia profusely. To allow rhizobia infect roots a suitable method of inoculation is important. In this research we compared four methods of inoculation; seed, soil, side (place inoculant 5 cm from seed) and side+seed. It was found that nodule number and weight were highest with soil inoculation and followed by seed, seed+side and side inoculation. Nodules were formed on both taproot and lateral roots when soil inoculation was applied. For seed inoculation most nodules were formed on tap root. It was interesting to find that under side inoculation no nodule was formed on tap root but formed on lateral roots where inoculant was placed. Nitrogen fixation and yield of soybean were not significantly different indicated that nodules formed on lateral roots were sufficient for notrogen fixation to supply N for soybeans. However, for the benefit of following crops soil inoculation should be recommended because high amount of nodules could increase soil fertility level.