Abstract
ln this papar the author investigated the types of humus of paddy soils by the Simon's method. The results are summarized as follows : (1) Humus extracted from the paddy soils (fallon slice) using NaF or NaOH solution was generally composed of humuc acids (rotted materials and true humic acids; 60-70 per cent) and fulvic acids (40-3) percent). (2) Humic acids were chiefly rotted materials, which conld be extracted only by NaOH, Besides, in case of the dry paddy soils, there were true humic acids equal to the amounts of about 30 percent of rotted materials, mainly cxtracted by NaF(On the other hand, in case of the wet paddy soils, true humic acids seemed not to exist. (3) Because of the fact that our rotted materials ad higher humification values than Simon's so-called rotted materials, further investigation is neccssary to characterize these humic acids.
