日本土壌肥料学雑誌

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The presence of podzol soils in Karafuto island has been known from early time but its character has never been cleared up in detail. The present investigation then was undertaken to elucidate this phase of the soil. Three soil samples considered as representative of Karafuto podzol were taken, viz, residual forest soils of tertiary shale and marine forest soil of sea shore sand from Horo located at the central part of the island and alluvial forest soils of river sand from Sikuka located at the northern part of the same were taken. They were studied morphologically and chemically. The climatic soil types of three soils were also discussed and determined. Tertiary shale soils of Horo were shown clearly to possess bleached horizon and "orterde"in this profile. Two other sandy soils from Horo and Sikuka were also shown to have remarkable bleached horizon and "ortstein". Humus in the profiles was found in all these soils accumulated in A_1white it was washed down in A_2. Some of the humus was deposited in B_1 as a result of removal from upper horizons. Complete and strong acid analysis of mineral portion indicated that the accumulation of sillica had occurred while the removal of sesquioxides and bases were seen in horizons A_1and A_2. The molecular rations of silica to alumina and alumina to bases calculated from the result of the analysis offered further proof on the accumulation and removal of the matters described above. The molecular ratio of alumina to bases in B horizon was calculated to be lower than 1 in every soil. This may be explained with the theory of isoelectric precipitation proposed by Mattson. The distributions of silica and sesquioxides extracted with acidammonium oxalate in each horizon were in good agreement with those presented by Lundblad who had used it as a characteristic to distinguish the podzol soils from brown earth. "Verwitterungsziffer K and B" proposed by Harrassowitz were calculated from the result of the complete analyses of A_2 and C horizons of each soil. The values found agreed with those presented by that same author, which indicates that the soils have undergone the podzolization process. The pH value of exchange neutrality of dialyzed soils of each of the horizons were determined. Neutral curves obtained agreed with those figured by Mattson, who has used these data as evidence of the podzolization. From the above it is clear that the three forest soils under examination should be classified as belonging to the group of the true podzol types. And then they should be called mature true podzol according to the naming proposed by Joffe.

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