MICRO-MORPHOLOGICAL STUDIES ON CLAY-AMENDED AND UNAMENDED LOAMY SAND, RELATING SURVIVAL OF INTRODUCED BACTERIA AND SOIL STRUCTURE

With the use of Cryo Scanning Electron Microscopy (SEM performed at low temperatures) the microstructure of clay- (bentonite and kaolinite) amended and unamended loamy sand was studied. A wide range of pore sizes could be recognized in all three treatments, but pore size distributions clearly differed between the soil types. The bentonite clay was present as a very porous matrix, containing pores with an average maximum length of approximately 3 mum, and an average minimum width of approximately 2 mum. Pores of similar sizes were also present in kaolinite- and unamended loamy sand, but they were much less frequent. Previous results, suggesting that the protective effects of bentonite clay on the survival of introduced bacteria in soil could be caused by an increase in the number of pores with an equivalent neck diameter < 6 mum, were confirmed.