Carbon mineralization and microbial activity in a field site trial used for 14C turnover experiments over a period of 30?years |
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Authors: | M Stemmer K Roth E Kandeler |
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Institution: | (1) Austrian Society for Soil Biology, Spargelfeldstrasse 191, A-1220 Vienna, Austria, AT;(2) Federal Agency and Research Centre for Agriculture, Spargelfeldstrasse 191, A-1220 Vienna, Austria, AT;(3) Institute of Soil Science, University of Hohenheim, Emil-Wolff-Strasse 27, D-70593 Stuttgart, Germany, DE |
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Abstract: | Long-term experiments on different crop management systems provide essential information about turnover of soil organic matter
and changes in microbial properties over a period of time. A long-term field site trial, which was established in 1967 near
Vienna, Austria, to document the fate of 14C-labelled manure (straw and farmyard) under different crop management systems (crop rotation, spring wheat and bare fallow),
was investigated. Soil samples were taken in 1997 and separated into size fractions (>250 μm, 250–63 μm, 63–2 μm, 2–0.1 μm
and <0.1 μm) after aggregate dispersion using low-energy sonication. Organic C, total N and 14C content were measured in the bulk soil and the size fractions and microbial properties were analysed in the bulk soil. Additionally,
C mineralization in bulk soil samples was monitored at 20 °C over a period of 28 days, and subsequently 14C-CO2 content was analysed. The distribution of organic C and N within the size fractions was similar between crop rotation and
spring wheat; the highest amounts of organic C and N were found in the clay-sized fraction. The amounts of C and N were significantly
smaller in the bare fallow, which was depleted of organic matter in the coarse-sized fractions. 14C distribution differed significantly from unlabelled C distribution, labelled C was accumulated in the silt-sized fraction,
indicating weak humification of the applied manure C. The highest rate of C mineralization was measured in the crop rotation
and spring wheat, whereas the emission rate of the bare fallow was about 40% lower. The higher 14C:C ratio of the bulk soil in comparison to the emitted CO2 indicated that labelled C compounds still remained mineralizable after a period of 30 years. Microbial properties showed
a great difference between crop management systems and bare fallow, particularly regarding urease and xylanase activity.
Received: 31 May 1999 |
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Keywords: | Carbon mineralization 14C Soil microbial biomass Manure amendment Long-term experiment |
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