Search

This thesis elucidates the influence of urban waste composts and biochar on the water holding capacity and the chemical composition of soil organic carbon. The urban waste composts increased soil carbon contents and stocks of the agricultural soils whereby the clay fraction acted as the main carbon sink. In biochar amended soils this shifted into the particulate organic matter fraction. No amendment affected the quality of the clay fraction. Despite minimal decomposition, biochar was found in all physical fractions after one year in soil. Aged biochar increased the microbial activity and carbon use efficiency under drought stress. Diese Arbeit erläutert den Einfluss von urbanen Abfallkomposten und Biokohle auf die Wasserhaltekapazität und die chemische Zusammensetzung des organischen Bodenkohlenstoffs. Urbane Abfallkomposte erhöhten Kohlenstoffgehalte und -vorräte der landwirtschaftlich genutzten Böden, wobei die Tonfraktion als wichtigste Kohlenstoffsenke fungierte. Bei Biokohlegaben verschob sich dies in die partikuläre organische Substanz. Die Qualität der Tonfraktion wurde von keinem Bodenhilfsstoff beeinflusst. Trotz minimalen Abbaus wurde Biokohle nach einem Jahr im Boden in allen physikalischen Fraktionen wiedergefunden. Unter Trockenstress steigerte gealterte Biokohle die mikrobielle Aktivität und Kohlenstoffnutzungseffizienz.

International audience; Organic amendments are widely used to enhance the fertility of cropland soils. However, there is only scarce knowledge about the long term impact of added organic matter (OM) on the soil organic carbon (SOC) pool. Therefore, we analyzed a long-term field experiment in Feucherolles (France), which regularly received three different composts (home sorted bio-waste mixed with green waste (BIO), municipal solid waste (MSW) and a mixture of green waste and sewage sludge (GWS) and cattle manure since 1998. With these organic materials approximately 4 Mg total OC were added to the soil in two year intervals. The experiment was fully randomized with 4 replicates for each amendment. In September 2013 we took samples from the surface soil (0-5 cm of Ap horizon) of all 4 treatments and the unamended control. To study the chemical alteration and the fate of the added OC into different soil compartments, we fractionated the soils by physical means using a combined density and particle size protocol. Carbon and N content were determined in bulk soils, amendments as well as in size fractions (fPOM, oPOM 20µm, sand, silt and a combined fine silt-clay fraction). Chemical composition was determined by solid-state 13C CPMAS NMR spectroscopy. We found significant higher C contents for the oPOM small and sand fraction of BIO treated soil and for the clay fraction of GWS treated soils (p