Abstract
In this paper, the form of humus was investigated according to the methods by SPRINGER and SIMON. The results may be summarized as follows : (I). Highly productive soil decreased in the amount of true humic acid, and increased in that of rotted product and the part soluble in acetylbromide, (2). Highly productive soil is low in the degree of humus decomposition (i.e.Z.G.) (3). The Daisen black soil is rich either in humin and lignin or in lignohumin. (4). Generally speaking, it seems that the humus in black soil is strongly combined with iron and aluminum and that it resembles to podzol, while in highly productive paddy soil (e.g. Yonezawa paddy soil), a part of humus is being isolated and is loosely combined with calcium and magnesium. (5) The humus in black soil has a jet black colour and it seems to the authors that in addition to the humus in ordinary form a special form of humus also exists in black soil. Judging from the colouring coefficient TF, field soil is of black soil type, while cultivated soil is of humolignin type peculiar to podzol. (6). The humus in black soil is generally small in its StF. Especially, highly productive soil has a stronger tendency to become smaller in the StF of the humus. (7). In its color-degree NaOH extracted solution is greater than that of NaF, and rotted product is also strongly coloured.
