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ORIGINAL ARTICLE

Exports and inputs of organic carbon on agricultural soils in Germany Anna Jacobs . Christopher Poeplau . Christian Weiser . Andrea Fahrion-Nitschke . Axel Don

Received: 16 January 2020 / Accepted: 28 July 2020 Ó The Author(s) 2020

Abstract The quantity and quality of organic carbon (Corg) input drive soil Corg stocks and thus fertility and climate mitigation potential of soils. To estimate fluxes of Corg as net primary production (NPP), exports, and inputs on German arable and grassland soils, we used field management data surveyed within the Agricultural Soil Inventory (n = 27.404 cases of sites multiplied by years). Further, we refined the concept of yield-based Corg allocation coefficients and delivered a new regionalized method applicable for

Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10705-020-10087-5) contains supplementary material, which is available to authorized users. A. Jacobs (&)  C. Poeplau  C. Weiser  A. Fahrion-Nitschke  A. Don Thu¨nen Institute of Climate-Smart Agriculture, Bundesallee 65, 38116 Brunswick, Germany e-mail: [email protected] A. Jacobs Coordination Unit Soil of Thu¨nen Institute, Bundesallee 49, 38116 Brunswick, Germany

agricultural soils in Central Europe. Mean total NPP calculated for arable and grassland soils was 6.9 ± 2.3 and 5.9 ± 2.9 Mg Corg ha-1 yr-1, respectively, of which approximately half was exported. On average, total Corg input calculated did not differ between arable (3.7 ± 1.8 Mg ha-1 yr-1) and grassland soils (3.7 ± 1.3 Mg ha-1 yr-1) but Corg sources were different: Grasslands received 1.4 times more Corg from root material than arable soils and we suggest that this difference in quality rather than quantity drives differences in soil Corg stocks between land use systems. On arable soils, side products were exported in 43% of the site * years. Cover crops were cultivated in 11% of site * years and contributed on average 3% of the mean annual total NPP. Across arable crops, total NPP drove Corg input (R2 = 0.47) stronger than organic fertilization (R2 = 0.11). Thus, maximizing plant growth enhances Corg input to soil. Our results are reliable estimates of management related Corg fluxes on agricultural soils in Germany. Keywords Carbon sequestration  Manure  Net primary productivity  Carbon balance  Net biome productivity

Present Address: C. Weiser Fachagentur Nachwachsende Rohstoffe e. V, Hofplatz 1, 18276 Gu¨lzow-Pru¨zen, Germany

Introduction Present Address: A. Fahrion-Nitschke Niedersa¨chsische Landesforsten, Forstplanungsamt, Forstweg 1A, 38302 Wolfenbu¨ttel, Germany

The content or stock of soil organic carbon (SOC) in agricultural soils is regarded as the key parameter

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Nutr Cycl Agroecosyst

sustaining soil fertility and health. Moreover, the carbon (C) cycle of agricultural systems plays a role in climate change mitigation: since the more C is stored as organic C (Corg) in the soil and the longer it is stored for, the l