Studies on the humus forms of forest soils |
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| Authors: | Seiichi Ohta Kyoichi Kumada |
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| Institution: | Faculty of Agriculture , Nagoya University , Nagoya , Japan |
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| Abstract: | Samples described in the previous paper were analyzed for humus composition by the method of Kumada el al,, elementary composition of humic acids, nitrogen distribution among humic acid, fulvic acid, and humin, and organic matter composition by the modified Waksman method. The samples obtained by physical fractionation from each horizon of Higashiyama soil were as follows: f1 and f2 from the L layer, f1, f2 and f3 from the F layer, f1 f2, sand, silt, and clay fractions from the H-A and A horizons. With the progress of decomposition, the following tendencies were rather clearly observed. The extraction ratio of soluble humus, amounts of humic acid and fulvic acid, and PQ, value tended to increase with some exceptions. The degree of humification of humic acid proceeded. Most humic acids belonged to the Rp type, but those of the clay fractions belonged to the B type. As for the elementary composition of humic acid, transitional changes from the Lf1 to the clay fraction of the A horizon were observed. But differences in elementary composition among humic acids were far less, compared with those among whole fractions. Nitrogen contents in humic, fulvic, and humin fractions increased with the progress of decomposition and humiliation, and the largest relative increase was found in fulvic acid nitrogen. According to the modified Waksman's method, the amounts of residues and protein increased, while the total amounts of each extract, except for the HCl extract, and the amounts of sugars and starch, phenolic substances, hemicelluloses and pectin, and cellulose decreased. Sugars and starch comprised only a small portion of the hot water extract, and polyphenols substances comparable to sugars and starch were also found in the extract. Hemicelluloses and pectin accounted for only about one-half of the HCl extract. Several characteristic differences in the elementary composition of extracts and residues were found. Pheopigments existed in benzene-ethanol extracts and their amounts seemed to decrease from Lf1 to Ff2. |
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| Keywords: | ANFIS ANNs regression soft computing surface soil shear strength |
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