Journal article
Effects of addition of maize litter and earthworms on C mineralization and aggregate formation in single and mixed soils differing in soil organic carbon and clay content

Publication Details
Wachendorf, C.; Potthoff, M.; Ludwig, B.; Jörgensen, R.
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tC mineralization and aggregate stability directly depend upon organic matter and clay content, and bothprocesses are influenced by the activity of microorganisms and soil fauna. However, quantitative data arescarce. To achieve a gradient in C and clay content, a topsoil was mixed with a subsoil. Single soils and thesoil mixture were amended with 1.0 mg maize litter C g soil-1with and without endogeic earthworms(Aporrectodea caliginosa). The differently treated soils were incubated for 49 days at 15◦C and 40% waterholding capacity. Cumulative C mineralization, microbial biomass, ergosterol content and aggregate frac-tions were investigated and litter derived C in bulk soil and aggregates were determined using isotopeanalyses. Results from the soil mixture were compared with the calculated mean values of the two singlesoils. Mixing of soil horizons differing in carbon and clay content stimulated C mineralization of addedmaize residues as well as of soil organic matter. Mixing also increased contents of macro-aggregate Cand decreased contents of micro-aggregate C. Although A. caliginosa had a stimulating effect on C miner-alization in all soils, decomposition of added litter by A. caliginosa was higher in the subsoil, whereas A.caliginosa decreased litter decomposition in the soil mixture and the topsoil. Litter derived C in macro-aggregates was higher with A. caliginosa than with litter only. In the C poor subsoil amended with litter,A. caliginosa stimulated the microbial community as indicated by the increase in microbial biomass. Fur-thermore, the decrease of ergosterol in the earthworm treated soils showed the influence of A. caliginosaon the microbial community, by reducing saprotrophic fungi. Overall, our data suggest both a decreaseof saprotrophic fungi by selective grazing, burrowing and casting activity as well as a stimulation of themicrobial community by A. caliginosa.

Last updated on 2019-01-11 at 16:03