Decomposition of plant residues used in no-tillage systems as revealed by flash pyrolysis
Changes in organic composition of crop residues (soybean, radish, white lupine, blue lupine, black oat and mucuna) that are utilized in crop rotations in no-tillage farming systems in the southern part of Brazil were evaluated by analytical flash pyrolysis. The pyrolysis allowed the identification of five groups of compounds in the residues: guaiacyl moieties in lignin (Lg), syringyl moities in lignin (Ls), polysaccharide (Ps), chlorophyll (Chl) and fatty acid (Fa) derivatives. The decomposition rates of the plant residues ranged from 4.7 to 5.9 g kg-1 day-1, with a mean value of 5.2 g kg-1 day-1, corresponding to a mean loss of 41% (37-47%) of the initial biomass after 80 days of incubation. The Ps and lignin contents were strongly affected by incubation; relative lignin content increased at the expense of polysaccharide derivatives. In the original samples, Ps was the principal group of organic compounds in green manure plant materials, with maximum values in blue and white lupine (67%); after incubation, Ps fractions decreased by 26-51% (average 40%), with the greatest value observed with mucuna and the lowest in white lupine. In soybean plant material the Ps fraction decreased only by 9%. Greater increases in relative lignin content were observed with Ls (156%) than with Lg (59%) derivatives, demonstrating that guaiacyl moieties are easier to biochemically degrade than syringyl moieties. A significant correlation between residue-weight loss and organic groups after 80 days incubation was only found with Ls. Plant materials showing a higher content of syringyl moieties after decomposition might aid in increasing soil organic matter. Flash pyrolysis was shown to be an adequate technique to follow the process of transformation of plant residues into stabilized soil organic matter.
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| Format: | artículo biblioteca |
| Language: | English |
| Published: |
Elsevier
2002
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| Online Access: | http://hdl.handle.net/10261/58408 http://dx.doi.org/10.13039/501100003593 |
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