DYNAMICS OF ROOT COLONIZATION OF ACID-TOLERANT RHIZOBIUM MELILOTI STRAINS IN AN ACID YELLOW SOIL

Three acid-tolerant strains of Rhizobium meliloti, 91522,91512 and 91532,were used to inoculate the rhizosphere of alfalfa on an acid yellow soil and calcium at different concentration was applied.All the 3 strains of R.meliloti colonized well in the soil and their colonization dynamics was similar.The effect of 91512 and 91532 inoculation was better than that of 91522.Ca application had little effect of R.meliloti colonization.Of the Ca concentrations used in the study,Ca~(2+) at 5 mmol/L gave the best result.Inoculation of the acid-tolerant R.meliloti strains significantly affected nodule weight per plant,root fresh weight,plant height,shoot fresh weight,total nitrogen and rhizobium colonization in the acid soil.Ca~(2+) application showed significant effects on root fresh weight,plant height,shoot fresh weight and nodule weight.It is thus concluded that moderate rate of Ca~(2+) application can improve the yield and quality of alfalfa on acid yellow soil.