PASSIVE MOVEMENT OF CHICKPEA AND BEAN RHIZOBIA THROUGH SOILS

The downward and upward movement of different rhizobia strains in soil s with flowing water were investigated. In a leaching experiment using saturated soil, the first appearance of cells in the leachate was sig nificantly affected by the characteristics of rhizobia and soils. The motility level of the rhizobia and movement aided by flagella did not contribute to the downward movement of rhizobia. Indeed, the presence of a high number of flagella impeded the movement of cells through por e necks. The presence of a limited number of large water-filled pores shortened the time of first appearance of flagellated cells. Compariso n of the leaching of chloride ions and rhizobial cells suggested that cells were being retained in soil by mechanical sieving. Retention of rhizobia was also demonstrated in an experiment which studied the upwa rd movement of rhizobia with flowing water into dry soil above a water table. Retention was most evident for flagellated cells.