DISTRIBUTION OF MICROORGANISMS IN SOIL AGGREGATES - EFFECT OF AGGREGATE SIZE

The distribution of microorganisms in soil aggregates with different diameters was determined using a ''washing and sonic vibration'' method. In humic rendzina the number of bacteria, actinomycetes and fungi located in aggregates measuring 3 to 1 and less than or equal to 0.5 mm was greater than in those of 7 to 5 mm. Pseudomonas were more numerous in aggregates of less than or equal to 0.5 mm than in those of 3 to 1 mm and spore-forming aerobic bacteria - in aggregates measuring 3 to 1 mm than in those of 7 to 5 mm. The number of microorganisms growing on asparagine agar and Arthrobacter - Corynebacterium increased as 7-5 < 3-1 < 0.5 and 7-5 < 0.5 < 3-1 mm, respectively. In podzolic loess spore-forming aerobic bacteria inhabited preferentially aggregates measuring 7 to 5 mm, Arthrobacter - Corynebacterium aggregates of less than or equal to 0.5 mm. The number of bacteria was greater in aggregates of 3 to 1 than in those measuring less than or equal to 0.5 mm. Aggregates of various diameters differed also in the number of some microorganisms both in the outer and inner parts and the partition ratio of microorganisms between these parts. Differences were more numerous in the humic rendzina aggregates.