A study on the soil for coating the stems of mat rushes

The authors investigated the geological systems and productive condition of producing districts of soils used for the coating of mat rushes in Hiroshima Prefecture and Hyogo Prefecture, collected samples of soils and examined the physical and chemical properties of these soils.

For chemical properties, hot hydrochloric acid analysis and total analysis of soil colloid were carried out and the calculated silica-alumina ratio, base exchange capacity and proportion of Fe++ and Fe+++, color reaction and dying of soil colloid were determined.

For physical properties, the soil colloid was separated by the sedimentation method and the quantity of colloid was determined. Specific gravity, dehydration curve, absorption power and variation of temperature of soil by exposing to the rays of the sun were determined.

1) The producing district in Hiroshima Prefecture is a region which centers in Mihara, Onomichi and Matsunaga, and is limited to the southeast region of Hiroshima Prefecture.
2) Geological system at Kamura, Hongo, Kanae, Takasu, Fukamachi, Shirahama, Tomoji, Mizuochi and Uenohara belongs to Palaeozoic, at Kajiyamada to Granite, and at Seto to Granite Porphyry.
3) Producing districts in Hyogo Prefecture are Okura and Okubo in Akashi, and their geological system belongs to Diluvium and form hillock.
4) Soil color is divided into five kinds such as whitish grey, light yellowish grey, yellowish
grey, light brownish grey and bluish grey. pH value shows 4.55 in the lowest and 6.70 in the highest.
5) Clay with particle diameter less than 0.002 mm is considered to be soil colloid. This was separated by the Pipette Method. Quantity of colloid is 39.65% in the highest, 8.32% in the lowest and 23.07% in average.
6) Relationship between soil color and pH value can not be recognized as a definite relation, but quantity of colloid has a tendency of being less in light-colored soil, and on the contrary, much more in dark-colored ones.
7) On the average, values of total nitrogen, Fe2 0 3, CaO and MgO in soils of Hyogo Prefecture are very much more, and K 20 and Na20 are a little more than in those in Hiroshima Prefecture.
8) On total analysis the amount of H 20, CaO and MgO is very much more but Fez03 and P20 5 are less in soil colloid of Hyogo Prefecture than in those of Hiroshima Prefecture.
9) SiOz/ Al203 and Si02 /R20 3 of colloid by total analysis are higher in Hyogo Prefecture, but the difference between them is not great.
10) Base exchange capacity of soil colloid in Hiroshima Prefecture is 21.6 m eq in the highest, 7.46 m eq in the lowest and 13.38 m eq in average. In Hyogo Prefecture it is 18.0 m eq and 13.3 m eq. Little differences between them are recognizable.
11) Quantity of Fe++ and Fe+++ is closely associated with soil color. Proportion of Fe++ and Fe+++ in whitish grey and yellowish grey soil is 10-14 to 86-90, and in brown soil Fe++ is decreased but Fe+++ is increased. In soils of Hyogo Prefecture the quantity of Fe++ is very much more than Fe+++, and the proportion is 90 to 10. Fe+++ is found more in Hiroshima Prefecture soils and Fe++ more in Hyogo Prefecture soils.
12) Results of color reaction by benzidine and dying by safranine T can be recognized that clay mineral of Kaolinite group is adulterated.
13) Specific gravity by picnometer is 2.730 in the highest, 2.248 in the lowest and 2.595 in average.
14) Dehydration curve examined at from 100oC to 900oC is similar to that of clay minerals such as Kaolinite and Halloysite.
15) Absorptive power of colloid seems to depend more upon soil property than upon the quantity.
16) Variation of temperature of soil used for the coating of mat rushes by exposing to the direct rays of the sun shows some different result owing to the kinds of soils.

Though discovering a substitute for soils used for the coating of mat rushes was the task of this study, in coating the stems, when the stems were treated with other materials such as bentonite or Japanese acid clay and dried and moreover when a finished mat was produced, commercial value as a mat was much reduced unless the usual soil was used.

Therefore under the present phase it does not solve the problem of a substitute. The quantity of production of the soil used for the coating of mat rushes in Hiroshima Prefecture seems to be less than in Hyogo Prefecture and the future reserves are also less. Hence we can use the soil produced at Akashi, Hyogo Prefecture as a substitute, but as mentioned before, the quality and property of Fe of Hyogo Prefecture soils are diferent from that of Hiroshima Prefecture. Since the color of the mat may be somewhat bluish, the commercial value is as yet uncertain.