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Effect of long-term tillage treatments on the temporal dynamics of water-stable aggregates and on macro-aggregate turnover at three German sites

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Andruschkewitsch, R.; Koch, H.; Ludwig, B.
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Zusammenfassung, Abstract
The protection of organic material within aggregates against microbial decomposition is regarded as an important process in soil organic carbon stabilization but detailed knowledge about this process is still lacking. The objective of our study was to determine the longer and short-term impacts of three different tillage treatments (conventional tillage, mulch tillage and no-tillage) on water stable aggregate size distribution. Soils from three sites with long-term tillage trials on loess soils in Germany, planted with sugar beet followed by two years of winter wheat, were sampled in 0-5 cm, 5-25 cm and 25-40 cm depth in April 2010 (wheat stand on all sites), September 2011 (before tillage, after wheat harvest or in the sugar beet), November 2011 (bare soil after tillage or after tillage and sowing of winter wheat) and April 2012 (bare soil or wheat stand). Generally, the soils under no tillage and mulch tillage showed higher yields of macro-aggregates and carbon contents of macro-aggregates in 0-5 cm soil depth than under conventional tillage for all sampling dates, probably mainly due to litter accumulation in the topsoil under reduced tillage treatments. Tillage in November 2011 showed no effect on macro-aggregate yield in comparison to earlier sampling in September 2011. This suggests that either the physical impact of the mouldboard plough did not markedly affect macro-aggregate dynamics or that high macro-aggregate rebuilding rates due to litter incorporation and soil mixing under conventional tillage counterbalanced the physical impact In 0-5 cm soil depth the carbon content of the micro-aggregates within macro-aggregates was higher under reduced tillage treatments, indicating accelerated macro-aggregate turnover under conventional tillage. In contrast it was lower in 5-25 cm under no tillage and 25-40 cm under mulch tillage and no tillage than under conventional tillage. Overall, the pattern of yields of macro-aggregates and carbon contents within macro-aggregates over time and depth suggests that the interaction of soil disturbance and litter incorporation of the different tillage treatments created a steady state in terms of macro-aggregate turnover within the different tillage treatments. (C) 2013 Elsevier B.V. All rights reserved.

Aggregate dynamics, Aggregate turnover, Long-term tillage

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Zuletzt aktualisiert 2019-25-07 um 19:35