Adsorption of the rhizosphere bacterium Azospirillum brasilense Cd to soil, sand and peat particles

Department of Plant Genetics, The Weizmann Institute of Science, Rehovot 76 100, Israel ABSTRACT Summary: The rhizosphere bacterium Azospirillum brasilense Cd adsorbed strongly to light-texture and heavy-texture soils, but only slightly to quartz sand. Increase in clay and organic matter content, decrease in soil pH, or flooding the soil enhanced adsorption, whereas the presence of a bacterial attractant, increase in soil pH or drying of the soil decreased adsorption. The cells adsorbed to the upper fraction of the soil profile, but were able to infiltrate deeper if very dry soil was wetted. Washing the soil did not desorb the bacteria from soil particles, but it did from the sand particles. Overwashing soil recovered relatively few cells, whereas overwashing sand detached most of the bacteria. Survival time of A. brasilense Cd was short in soil but long in peat inoculant. Present address: Department of Agronomy, Ohio State University, Columbus, Ohio 43210, USA.