Soil management system effects on size fractionated humic substances

Citation
Eh. Novotny et al., Soil management system effects on size fractionated humic substances, GEODERMA, 92(1-2), 1999, pp. 87-109
Citations number
54
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Agriculture/Agronomy
Journal title
GEODERMA
ISSN journal
0016-7061 → ACNP
Volume
92
Issue
1-2
Year of publication
1999
Pages
87 - 109
Database
ISI
SICI code
0016-7061(19990915)92:1-2<87:SMSEOS>2.0.ZU;2-H
Abstract
The humic substances (HS) of two Brazilian Oxisols, one under native grassl and (NG) and the other submitted to a long-term (19-year) tillage systems e xperiment including no-tillage (NT), minimal tillage (MT) and an adjacent e ucalyptus-planted forest (F), were extracted with sodium pyrophosphate, ana lysed and fractionated by exclusion chromatography on controlled pore glass (CPG). Chromatographic analysis of HS was performed at 400 nm (visible reg ion), the resulting chromatograms deconvoluted and statistical analysis of data made using multivariate methods (factor and Pearson correlation analys is). Increase of tillage intensity, estimated by factor analysis, resulted in a general HS content decrease, not affecting soil C content. Tillage inc reased the relative proportion of small molecular size HS, determined direc tly by CPG and indirectly by the relative increase of fulvic acids (FA) con tent (increase of fulvic acids/humic acids ratio). This suggests that tilla ge caused preferential degradation of large molecular size HS and/or a neo- synthesis of small HS due to increased fresh-carbon input partially induced by liming and fertilisation. The HS fractionation method on CPG permitted gray humic acids (GHA) separation into two distinct fractions. The larger m olecular size fraction showed an unusual high E-4/E-6 ratio, possibly due t o a small conjugation of aromatic rings. (C) 1999 Elsevier Science B.V. All rights reserved.