Exports and inputs of organic carbon on agricultural soils in Germany

Anna Jacobs,Christopher Poeplau,Christian Weiser,Axel Don,Andrea Fahrion-Nitschke

doi:10.1007/s10705-020-10087-5

Anna Jacobs, Christopher Poeplau + Show 3 more

Open Access

https://doi.org/10.1007/s10705-020-10087-5

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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 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.

Highlights

The content or stock of soil organic carbon (SOC) in agricultural soils is regarded as the key parameter sustaining soil fertility and health
There are five main pathways of Corg input to agricultural soils, governed by: (1) type and amount of aboveground harvest residues if left in the field, stubbles always remaining in the field or mulch if left in the field, (2) type and amount of organic fertilizers applied, (3) type and amount of excreta produced by grazing animals, (4) cover crops used for green manure, and (5) belowground biomass as dead roots and rhizodeposition
Net primary production on and export of organic carbon from arable and grassland sites The majority of crops cultivated on German arable soils between 2001 and 2015 were winter wheat, silage maize, oil seed rape, and winter barley which were cultivated in 65% of all arable site * years evaluated (Table 2)

Summary

Introduction

The content or stock of soil organic carbon (SOC) in agricultural soils is regarded as the key parameter sustaining soil fertility and health. There are five main pathways of Corg input to agricultural soils, governed by: (1) type and amount of aboveground harvest residues if left in the field, stubbles always remaining in the field or mulch if left in the field, (2) type and amount of organic fertilizers applied, (3) type and amount of excreta produced by grazing animals, (4) cover crops used for green manure, and (5) belowground biomass as dead roots and rhizodeposition This implies that agricultural soils have C-sink potential and that implementation of certain management practices could help mitigate climate change (Minasny et al 2017)

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