Watanabe, Akira and Sarno, - and Lumbanraja, Jamalam and Tsutsuki, Kiyoshi and Kimura, Makoto (2001) Humus composition of soils under forest, coffee and arable cultivation in hilly areas of south Sumatra, Indonesia. European Journal of Soil Science, 52. pp. 599-606. ISSN 1365-2389

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To understand the effect of land use changes on the composition of humus in tropical soils, samples from land under primary forest, secondary forest, coffee plantation, and arable crops were investigated at three sites in south Sumatra, Indonesia. Total carbon and total nitrogen contents were 1.7 to 4.3 times and 1.1 to 2.8 times greater in the topsoil under primary forest than under the other types of land use. Following change from primary forest to other uses, the proportion of humic acids in the organic matter of the topsoils decreased while that of the fulvic acid fraction increased. Within the range of land uses, differences in the yields of humic acids and fulvic acid fractions were, respectively, larger and smaller than those in total carbon content. The humic acids were classi®ed into the low and middle classes in the degree of humi®cation. Absorption due to the green fraction of humic acids, Pg, was detected in the Uvvisible spectra of almost all the humic acids. No relation was observed between the degree of humi®cation of humic acids or the strength of Pg absorption in their spectra and land use change. The fulvic acid fractions were fractionated on insoluble polyvinylpyrrolidone (PVP) into the adsorbed fractions consisting of humic substances and the non-adsorbed fractions consisting of non-humic substances. A positive correlation between the amount of the fulvic acid fraction and the percentage of the PVP-adsorbed fraction within it indicated that the variation in the amount of the fulvic acid fraction was attributable to acid-soluble humic substances. The ionization difference spectra of solutions between pH 12 and pH 7 suggested that the chemical structures of the PVP-adsorbed fulvic acids have been altered by land use change.

Item Type: Article
Subjects: S Agriculture > S Agriculture (General)
Divisions: Fakultas Pertanian (FP) > Prodi Ilmu Tanah
Depositing User: SARNO
Date Deposited: 04 Nov 2016 02:48
Last Modified: 04 Nov 2016 02:48
URI: http://repository.lppm.unila.ac.id/id/eprint/1014

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