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CaCO3 in agroecosystems as a source of atmospheric CO2 by nitrogen fertilization

Subject Area Soil Sciences
Term from 2020 to 2024
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 441739623
 
Final Report Year 2024

Final Report Abstract

Carbonate-containing minerals comprise an additional form of soil carbon known as soil inorganic carbon (SIC). Although SIC stocks are large, they have been neglected in most studies of carbon sequestration. In this project, we demonstrate the importance of SIC in the global C cycle and ecosystem functions. We have shown how pH regulation by SIC provides a unidirectional, significant source of CO2 in agroecosystems. In particular, we have studied the mechanisms of soil acidification, mainly through the application of nitrogen (N) fertilizers, but we have also shown the propagation of the acidification front down into the soil profile over time, leading to the contribution of subsoil SIC stocks to soil CO2 emissions. We also tested the acidification potential of common fertilizer types at different temperatures (10 and 25 °C), analyzed the effects of plant traits, i.e. N-use efficiency and N-fixation capacity, and studied the dynamics of SIC under anaerobic conditions. In addition, we assessed future SIC losses under anticipated global change processes such as increased N deposition and fertilization, elevated CO2, invasive plant distribution, and climate change. Finally, we discussed how SIC losses may destroy various soil functions and ecosystem services, but also impose significant economic and social costs that have not been properly considered. In summary, it is critical to consider that unlike organic carbon, SIC losses are irretrievable and that when SIC stocks are depleted, soils are vulnerable to a wide range of degradation factors, including erosion, surface and subsurface compaction, acidification, and nutrient depletion.

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