Abstract
Abstract Generally, from the viewpoint of soil physics, the cultivated land where soil is abundant in aggregates, especially water-proof ones, has high agricultural productivity. On the other hand, the formation and maintenance of soil aggregates is one of the effective method of the land conservation. In this paper, at first, we propose a method that the degree of aggregation is represented by the variation between the gradation analysis curves before and after dispersion, and secondly investigate especially the factors contributing to aggregate formation and the following conclusions are obtained.
(1). In the natural aggregates, the range of diameter where the aggregates are of a maximum amount is between 0.01 and 0.025 mm.
(1). In the natural aggregates, the range of diameter where the aggregates are of a maximum amount is between 0.01 and 0.025 mm.
(2). Though cation (Ca++) is effective to the formation of relatively micro-aggregates, organic matter is more effective to the macro-ones.
(3). It is desirable that the expression of soil structure by the three phase is converted to four phases by dividing the solid phase into the phases of soil particle and organic matter.
(4). It is suggested that aggregate formation is dependent upon an interaction between cation and organic matter. Furthermore, when the aggregates are created artificially, the ratio of 15% Ca to 5% organic matter seems the most profitable addition for a virgin soil.
