Nitrogen fixation and CO2exchange in soybeans (Glycine maxL.) inoculated with mixed cultures of different microorganisms

摘要

N2fixation, photosynthesis of whole plants and yield increases in soybeans inoculated with mixed cultures ofBradyrhizobium japonicum110 andPseudomonas fluorescens20 orP. fluorescens21 as well asGlomus mosseaewere found in pot experiments in gray forest soil carried out in a growth chamber. The effects of pseudomonads and vesicular-arbuscular (VA) mycorrhizal fungus on these parameters were found to be the same. Dual inoculation of soybeans with mixed cultures of microorganisms stimulated nodulation, nitrogenase activity of nodules and enhanced the amount of “biological” nitrogen in plants as determined by the15N dilution method in comparison to soybeans inoculated with nodule bacteria alone. An increased leaf area in dually infected soybeans was estimated to be the major factor increasing photosynthesis.P. fluorescensandG. mosseaestimulated plant growth, photosynthesis and nodulation probably due to the production of plant growth-promoting substances. Increasing phosphorus fertilizer rates within the range of 5–40 mg P 100 g-11:1 (v/v) soil: sand in a greenhouse experiment led to a subsequent improvement in nodulation, and an enhancement of N2fixation and yield in soybeans dually inoculated withB. japonicum110 andP. fluorescens21. These indexes were considerably higher in P-treated plants inoculated with mixed bacterial culture than in plants inoculated with nodule bacteria