Tillage practice influences on the physical protection, bioavailability and composition of particulate organic matter |
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Authors: | M M Wander M G Bidart |
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Institution: | (1) Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, IL 61801, USA e-mail: mwander@uiuc.edu Tel.: +1 217 333 9471 Fax: +1 217 244 3219, US;(2) Department of Ecology, Ethology and Evolution, University of Illinois, Urbana, IL 61801, USA, US |
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Abstract: | This study was conducted to determine whether separation of particulate organic matter (POM) that is biologically labile
from aggregate entrapped material improves the usefulness of POM as an index of soil C and N dynamics. The effects of conventional
(CT) and no-tillage (NT) practices on POM were assessed using soils from three 10-year trials in Illinois. Loose and occluded
POM in the 0–5 cm depth were separated from 1994 samples. Use of NT practices increased C and N contents at 0–5 cm relative
to CT practices and those increases were most apparent in the occluded POM fraction. The correlation between total POM-N and
potentially mineralizable N (PMN) was stronger than that between PMN and either the loose or occluded-POM fractions. In 1995,
both the microbial biomass, estimated as chloroform-labile C (CFEC), and PMN were correlated with POM-C and N, but the relationship
was weak when data (from different tillage and depth combinations) were not treated in aggregate. POM-C and CFEC were most
strongly correlated in surface depths and in CT treatments. In NT 0–5 cm samples, PMN contents were similar (≈27 mg N kg–1 soil) at all sites despite notable differences in POM-N concentrations; PMN was not related to POM-N in CT samples. There
was no consistent relationship between PMN and POM-N contents in 5–30 cm samples. DRFTIR spectra indicated that carbohydrates
were most abundant in POM at 0–5 cm. Relatively low PMN rates and enrichment of polysaccharides in POM in the sicl soil suggest
that physical protection of labile organic substrates was more important at that site than at sites with lighter textured
soils. Improved fractionation and incubation techniques and alleviation of laboratory artifacts will improve our ability to
relate POM quantity, distribution and composition to biologically mediated C and N dynamics occurring in the field.
Received: 2 December 1999 |
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Keywords: | Particulate organic matter Tillage practices C and N dynamics Physical protection Potentially mineralizable N |
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