Autor:innen:
Laura Skadell | Thünen Institute of Climate-Smart Agriculture | Germany
Florian Schneider | Thünen Institute of Climate-Smart Agriculture
Martina Gocke | University of Bonn, Institute of Crop Science and Resource Conservation (INRES), Soil Science and Soil Ecology
Julien Guigue | Technical University of Munich, TUM School of Life Sciences, Chair of Soil Science
Wulf Amelung | University of Bonn, Institute of Crop Science and Resource Conservation (INRES), Soil Science and Soil Ecology
Sara Bauke | University of Bonn, Institute of Crop Science and Resource Conservation (INRES), Soil Science and Soil Ecology
Eleanor Hobley | Technical University of Munich, TUM School of Life Sciences, Chair of Soil Science; Central Office for Information Technology in the Security Sector
Dietmar Barkusky | Leibniz Centre for Agricultural Landscape Research (ZALF) e.V.
Bernd Honermeier | Justus Liebig University Gießen, Institute of Agronomy and Plant Breeding I
Ingrid Kögel-Knabner | Technical University of Munich, TUM School of Life Sciences, Chair of Soil Science; Technical University of Munich, Institute for Advanced Study
Urs Schmidhalter | Technical University of Munich, TUM School of Life Sciences, Chair of Plant Nutrition
Kathlin Schweitzer | Humboldt University Berlin, Thaer Institute of Agricultural and Horticultural Sciences
Sabine Seidel | University of Bonn, Institute of Crop Science and Resource Conservation (INRES), Crop Science
Stefan Siebert | Georg August University Göttingen, Department of Crop Sciences
Michael Sommer | Leibniz Centre for Agricultural Landscape Research (ZALF) e.V.
Yavar Vaziritabar | Justus Liebig University Gießen, Institute of Agronomy and Plant Breeding I
Axel Don | Thünen Institute of Climate-Smart Agriculture
Soil organic carbon (SOC) stocks and δ13C, δ15N, and C/N values as indicators for soil organic matter quality are important parameters for soil health and ecosystem services such as carbon sequestration. Agricultural management can affect these parameters but it is uncertain to what extent and to what soil depth. We sampled and analysed the upper metre of cropland soils from ten German long-term experiments (LTEs) to quantify depth-specific effects on SOC stocks and on SOC quality of common agricultural management practices: mineral fertilisation, irrigation, a crop rotation with legumes, straw incorporation, application of farmyard manure (FYM), liming, reduced tillage and soil compaction. Results showed that 19±3 % of total management effects on SOC stocks were found in the upper subsoil (30 50 cm) and 3±4 % in the lower subsoil (50-100 cm), including all agricultural management practices with significant topsoil SOC effects. In the topsoil (0-30 cm), 79±7 % of management effects were found. Mineral fertilisation was the treatment that had the greatest effect on SOC stocks in subsoil, followed by irrigation, FYM application and straw incorporation. Sampling down to a depth of 50 cm resulted in significantly higher SOC effects than when considering topsoil only. Also, SOC quality in topsoil and subsoil was affected by the agricultural management. The analyses of δ13C and δ15N values revealed that liming and FYM had the largest effects on δ13C in topsoil and subsoil, resulting in an average reduction of 0.5 ‰ (FYM) and 0.2 ‰ (liming). Changes in δ15N with agricultural management allow conclusions on nutrient dynamics, however, locally detected δ15N peaks within experimental field sites require further investigations to ensure that only the potential management effects are analysed. Since approximately 20 % of the impact of agricultural management on SOC stocks occurs in the subsoil, we recommend soil monitoring programs and carbon farming schemes extend their standard soil sampling down to 50 cm depth to fully capture agricultural management effects on SOC and also consider effects on SOC quality.