Relation between Soil Erosion and Soil Characteristics

Abstract

The writer carried out some investigations on the relation between the amount of soil losses and some physico-chemical properties of soils in Tama. Upland. Soils in his field are classified as follows: Soils in St. 1, St. 2 and St. 3 are Kanto Loam, and those in St. 4 and St. 5 are soils from Pliocene, series. Conclusions of this paper are as follows:- (1) Soils derived from Pliocene series-especially St. 4-hav small degree of aggregates, therefore they cause severe runoff and erosion. (2) Soils from. Pliocene series (St. 4, 5.) have small degree of base saturation, hence they have small degree of aggregates and are unstable to rain wash. (3) Soils in which humus content is very small (especially St. 4) acarcely cause aggregation, and they have small absorption and permeability of water, so these soils are sucseptible to erosion. (4) Lower liquid limit of soils derived from Pliocene series (St. 4 and, St. 5) is small (about 40%) and that of Kanto Loam soils is great (about 70%). sothe former soils are unstable to water erosion. (5) The silica-sesquioxide ratio appears to be the most significant indexof erodibility obtainable by chemical analysis. It is an index of the degree of weathering, and, as a result, of erodibility. That is to say, the soils which have small ratio of silica-sesquioxide are resistible to dispersion and erosion. SiO2/R2O3 of any Kantõ Loam soil is smaller than 2.0, so they resistible to erosion, and those of siols derived from Pliocene series are larger than 2.0, so they are susceptible to erosion. (6) Generally speaking, physico-chemical properties of Kantõ Loam soils are more resistible to erosion than those derived from Pliocene series.