腐植化過程に關する微生物學的研究

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We investigated the effect of several microbes on the transformation of soirhumus: 0.5 g of N/8 NaOH-soluble humus, or of N/8 NaF-soluble humus, was mixed with 20 g of clean washed white sand in each respective flask and 14 cc of nutrient solution was added to it ; after sterilizing, the flasks, in which the microbes were inoculated, were incubated at 30°C ; during the period of incubation, the amount of CO2 evolved was determined at several times and after a certain period the form of humus was examined by the SIMON method. The results obtained were as follows: (1) Under the conditions of this experiment, Act. chromogenes, Act. unchromogenes, Pseud. fluorescence liquefascience, B. prodigiosus, H. mycoides and B. subtilis showed no effect on the transformation of NaOH-soluble humus. But Trichoderma konigni and soil extract acted on the sample, produced a considerable amount of CO2 gas, and after 74 days' incubation, the alkali extract of the sample resulted in an increase of the relative colour value (RF) and the precipitation quotient (PQ), and a decrease of the colour tone factor (TF). This shows that the humification of the sample was promoted. Even in this case, however, there was no change in the form of precipiation of the humus extract(humus acid). On the other hand, the carbbn-nitrogen ratio of the fulvic acid fraction of the Trichoderma plot was lowered to about a half of that of the Actinomyces plot or of the control plots From these facts, it is acknowledged that the effect on humification is, in the first place, revealed in the transformation of fulvic acid fraction. (2) NaF-soluble humus (mainly the true humic acid) was also acted on by Trichoderma, and after 38 days' incubation the relative colour value (RF) and the precipitation quotient(PQ) of the alkali extract became higher than that of the sample before the experiment. The true humic acid (die echte Huminsäure) is understood to be considerably stable to the microbio-logical activity, but, from the above facts, the true humic acid, especially brown humic acid, seems to be acted on by microbes if it is in the free state. The stability of the true humic acid in the soil may originate in forming the complex with inorganic colloids.