Alfalfa inoculation: The effect on root growth and number of rhizospheric microorganisms

Abstract

The root of alfalfa deeply penetrates the soil, improving soil structure, aeration and biological activity at greater depths. The rhizosphere of alfalfa abounds in different microorganisms which can have either a different effect on the root development. The aim of the research was to investigate the effect of nitrogen-fixing bacteria (Sinorhizobium meliloti and Azotobacter chroococcum) and phytopahtogenic fungi (Colletotrichum trifolii and Colletotrichum destructivum) on the root development and on the number of microorganisms in the rhizospheric soil of alfalfa varieties (Affinity, Perry and K-28). The use of rhizobia and azotobacter diminished the deleterious effect of the phytopathogenic fungi. The greatest root length was recorded in K-28 variety with the application of C. trifolii (Coll-4) in combination with S. meliloti, as well as in Perry variety with the application of C. destructivum (Coll-11 and CC657) in combination with R. meliloti. In comparison with the control, the greatest increase in nodulation was recorded in Perry variety whereas the smallest increase was recorded in K-28 variety. The total number of microorganisms in the rhizosphere of alfalfa increased only in some inoculated variants. The number of azotobacter increased several times in the variants where it was introduced which points to its good survival rate. © 2014 University of Bucharest.