Abstract
The micro-aggregates which were usually known in concerning to the deggregation of soil crumbs or the aggregation of single particles of soils had not been investigated for details. In this paper the authers reported the size distribution and durability of secondary particles as follows : (1) The diameters of secondary particles were from 0.06 mm to 0.02 mm. Two peaks were in the distribution-curves; and the diameter of larger particles were two times as larger as that of the smaller. (2) The durabillity of water-stable aggregates could be designated as follows; W=A/t^b (or log W=a-b log t). W=soil fraction larger than 0.06 mm (or 0.02 mm), t=time of shaking. (3) Cultivation or air-drying of soils decreased the degree of water stability of soil crumbs. (4) Sub-soils (B-horizon) did not disperse to the diameter as less than 0.02 mm. This was a typical characteristic of sub-soils, different from top-soils (A-horizon).
