Topsoil dilution, soil erosion and fertilization: Important findings on soil carbon storage

A recent study by the Leibniz Centre for Agricultural Landscape Research (ZALF) shows that the use of organic nitrate fertilizers, such as liquid manure or fermentation residues, in combination with topsoil dilution increases carbon storage in the soil and can thus contribute to climate protection. According to the study, the method of topsoil dilution, in which low-carbon subsoil is mixed into the topsoil, has less influence on the soil's ability to store carbon than the type of fertilization and the erosion status of the soil. The research results were published in the journal Science of the Total Environment.

The method of topsoil dilution is intended to contribute to climate protection in agriculture. The abrupt addition of subsoil to the topsoil, for example through partial deep plowing, creates a carbon deficit in the topsoil, which is to be compensated for with carbon from the atmosphere. However, depending on how much the topsoil has already been diluted by erosion, this technique does not always achieve the desired effect. It can also have various disadvantages, such as a lower water retention capacity of the soil.

Although dilution of the topsoil by mixing it with subsoil material reduced the loss of carbon from the soil in some cases in the study, it was less effective than the other factors of organic fertilization and protection of the soil from erosion. Shrijana Vaidya, research associate in the Isotope Biogeochemistry group at ZALF and one of the lead authors of the study, explains: “Our results show that it is crucial to consider the form of fertilizer and the erosion status of the soil in order to optimize carbon storage. Particularly in eroded soils, the combination of organic fertilizer, for example from liquid manure or fermentation residues, and topsoil protection can lead to effective carbon storage.”

These findings are of particular importance as agricultural soils worldwide can play an important role in storing carbon and thus potentially reducing CO₂ emissions in the atmosphere. Understanding how different agricultural practices influence carbon dynamics can help to develop targeted measures for farms that both maintain soil fertility in the long term and promote climate protection.

As part of this study, the researchers used a carbon flux measurement system to measure the influence of various factors on carbon storage in soils. The core of the Sensor Platform AgroFlux measuring platform is the FluxCrane, consisting of a gantry crane bridge and gas exchange hoods. The FluxCrane is an automated measuring system with which it is possible to measure gas exchange processes on agricultural land, as well as temporal and spatial dynamics of CO₂, water and greenhouse gas cycles in agricultural landscapes.

Note to the text:

This is a summary of the original text created with the help of artificial intelligence: Vaidya, S., Hoffmann, M., Dubbert, M., Kramp, K., Schmidt, M., Verch, G., Sommer, M., Augustin, J. (2024) Topsoil dilution by subsoil admixture had less impact on soil organic carbon stock development than fertilizer form and erosion state. Science of the Total Environment 946, Article 174243. https://doi.org/10.1016/j.scitotenv.2024.174243, published under license CC BY 4.0 https://creativecommons.org/licenses/by/4.0/.

The text has been carefully reviewed and revised in the light of the AI regulations at ZALF.

Funding reference

This study was funded by the Federal Ministry of Food and Agriculture (FNR Grant: 22404117).

Further information:

Study: Topsoil dilution by subsoil admixture had less impact on soil organic carbon stock development than fertilizer form and erosion state. https://doi.org/10.1016/j.scitotenv.2024.174243

Further articles on AgroFlux:

Benefits of a robotic chamber system to determine evapotranspiration in an erosion-affected heterogeneous cropland. https://hess.copernicus.org/articles/27/3851/2023/

A novel robotic chamber system for the accurate and precise determination of spatio-temporal CO 2 flux dynamics in heterogeneous cropland. https://www.sciencedirect.com/science/article/pii/S0168192320303087?via%3Dihub

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ZALF's AgroFlux Sensor Platform measuring station | Quelle: © Marten Schmidt / ZALF.

A ZALF study shows that organic fertilization in combination with the technique of topsoil dilution helps to store carbon in the soil. As part of the study, researchers used ZALF's AgroFlux Sensor Platform measuring station to record carbon emissions from agricultural soils. | Quelle: © Marten Schmidt / ZALF.