Rapid transformations of plant water-soluble organic compounds in relationto cation mobilization in an acid Oxisol

Citation
Jc. Franchini et al., Rapid transformations of plant water-soluble organic compounds in relationto cation mobilization in an acid Oxisol, PLANT SOIL, 231(1), 2001, pp. 55-63
Citations number
30
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Environment/Ecology
Journal title
PLANT AND SOIL
ISSN journal
0032-079X → ACNP
Volume
231
Issue
1
Year of publication
2001
Pages
55 - 63
Database
ISI
SICI code
0032-079X(200104)231:1<55:RTOPWO>2.0.ZU;2-N
Abstract
The maintenance of plant residues on the surface of acid soils in no-tillag e cropping systems reportedly increases the downward mobility of Ca and Al. This study investigated the effects of application of aqueous extracts of residues of radish (Raphanus sativus), blue lupine ( Lupinus angustifolius) , black oat ( Avena strigosa), soybean (Glicine max), and wheat (Triticum a estivum), without incubation (initial extract) or incubated (15-day extract ), on the chemistry of an acid Oxisol in 0.20-m columns. The application of initial extracts of plant residues increased the pH and the KCl-extractabl e contents of Ca2+, Mg2+ and Mehlich 1-extractable K+, and decreased the KC l-extractable Al3+ in the following order: blue lupine > radish > black oat > soybean > wheat. The Ca concentrations of the effluents, after applicati on of the initial extracts of radish and blue lupine, were virtually the sa me as those in the extracts before application, whereas K was decreased by 40 - 90%, and more Al was extracted from the soil than the amount determine d as KCl-extractable Al. The initial and 15-day extracts had similar effect s on soil Ca and Al, however, the capacity of mobilizing Ca and Al was mark edly decreased in the latter. This difference was associated with the type and relative composition of organic compounds in the water soluble organic fraction in both extracts as determined by gas chromatography-mass spectrom etry (GC-MS). The concentration of water soluble organic compounds in the f resh green manures residues became drastically decreased (50% on average) a fter the incubation. The initial extracts of blue lupine and radish had a h igh proportion (20 and 30%, respectively) of the organic compounds as short -chain fatty acids with a high capacity of forming stable complexes with Ca and Al. In contrast, the 15-day extracts were predominated by long-chain f atty acids and aromatic compounds, which did not show the same effect. Fres h green-manure residues had water-soluble organic compounds of low molecula r weight with high capacity of forming stable complexes with Ca and Al. The biological oxidation of these organic compounds occurred rapidly, markedly decreasing the capacity to mobilize cations in the aqueous plant-residue e xtracts.