Articles | Volume 22, issue 12
https://doi.org/10.5194/bg-22-2733-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-22-2733-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
17 Jun 2025
Research article |
| 17 Jun 2025
| 17 Jun 2025
Depth effects of long-term organic residue application on soil organic carbon stocks in central Kenya
Claude Raoul Müller
CORRESPONDING AUTHOR
Department of Environmental Systems Science, ETH Zurich, 8092 Zurich, Switzerland
Johan Six
Department of Environmental Systems Science, ETH Zurich, 8092 Zurich, Switzerland
Daniel Mugendi Njiru
Department of Land and Water Management, University of Embu, P.O. Box 6-60100, Embu, Kenya
Bernard Vanlauwe
International Institute of Tropical Agriculture (IITA), c/o ICIPE Compound, P.O. Box 30772–00100, Nairobi, Kenya
Marijn Van de Broek
Department of Environmental Systems Science, ETH Zurich, 8092 Zurich, Switzerland
Related authors
Claude Raoul Müller, Johan Six, Liesa Brosens, Philipp Baumann, Jean Paolo Gomes Minella, Gerard Govers, and Marijn Van de Broek
SOIL, 10, 349–365, https://doi.org/10.5194/soil-10-349-2024, https://doi.org/10.5194/soil-10-349-2024, 2024
Short summary
Short summary
Subsoils in the tropics are not as extensively studied as those in temperate regions. In this study, the conversion of forest to agriculture in a subtropical region affected the concentration of stabilized organic carbon (OC) down to 90 cm depth, while no significant differences between 90 cm and 300 cm were detected. Our results suggest that subsoils below 90 cm are unlikely to accumulate additional stabilized OC through reforestation over decadal periods due to declining OC input with depth.
Johan Six, Sebastian Doetterl, Moritz Laub, Claude R. Müller, and Marijn Van de Broek
SOIL, 10, 275–279, https://doi.org/10.5194/soil-10-275-2024, https://doi.org/10.5194/soil-10-275-2024, 2024
Short summary
Short summary
Soil C saturation has been tested in several recent studies and led to a debate about its existence. We argue that, to test C saturation, one should pay attention to six fundamental principles: the right measures, the right units, the right dispersive energy and application, the right soil type, the right clay type, and the right saturation level. Once we take care of those six rights across studies, we find support for a maximum of C stabilized by minerals and thus soil C saturation.
Antoine de Clippele, Astrid C. H. Jaeger, Simon Baumgartner, Marijn Bauters, Pascal Boeckx, Clement Botefa, Glenn Bush, Jessica Carilli, Travis W. Drake, Christian Ekamba, Gode Lompoko, Nivens Bey Mukwiele, Kristof Van Oost, Roland A. Werner, Joseph Zambo, Johan Six, and Matti Barthel
Biogeosciences, 22, 3011–3027, https://doi.org/10.5194/bg-22-3011-2025, https://doi.org/10.5194/bg-22-3011-2025, 2025
Short summary
Short summary
Tropical forest soils as a large terrestrial source of carbon dioxide (CO2) contribute to the global greenhouse gas budget. Despite this, carbon flux data from forested wetlands are scarce in tropical Africa. The study presents 3 years of semi-continuous measurements of surface CO2 fluxes within the Congo Basin. Although no seasonal patterns were evident, our results show a positive effect of soil temperature and moisture, while a quadratic relationship was observed with the water table.
Marijn Van de Broek, Fiona Stewart-Smith, Moritz Laub, Marc Corbeels, Monicah Wanjiku Mucheru-Muna, Daniel Mugendi, Wycliffe Waswa, Bernard Vanlauwe, and Johan Six
EGUsphere, https://doi.org/10.5194/egusphere-2025-2287, https://doi.org/10.5194/egusphere-2025-2287, 2025
This preprint is open for discussion and under review for SOIL (SOIL).
Short summary
Short summary
To improve soil health and increase crop yields, organic matter is commenly added to arable soils. Studying the effect of different organic amenmends on soil organic carbon sequestration in four long-term field trials in Kenya, we found that only a small portion (< 7 %) of added carbon was stabilised. Moreover, this was only observed in the top 15 cm of the soil. These results underline the challenges associated with increasing the organic carbon content of tropical arable soils.
Roxanne Daelman, Marijn Bauters, Matti Barthel, Emmanuel Bulonza, Lodewijk Lefevre, José Mbifo, Johan Six, Klaus Butterbach-Bahl, Benjamin Wolf, Ralf Kiese, and Pascal Boeckx
Biogeosciences, 22, 1529–1542, https://doi.org/10.5194/bg-22-1529-2025, https://doi.org/10.5194/bg-22-1529-2025, 2025
Short summary
Short summary
The increase in atmospheric concentrations of several greenhouse gases (GHGs) since 1750 is attributed to human activity. However, natural ecosystems, such as tropical forests, also contribute to GHG budgets. The Congo Basin hosts the second largest tropical forest and is understudied. In this study, measurements of soil GHG exchange were carried out during 16 months in a tropical forest in the Congo Basin. Overall, the soil acted as a major source of CO2 and N2O and a minor sink of CH4.
Marijn Van de Broek, Gerard Govers, Marion Schrumpf, and Johan Six
Biogeosciences, 22, 1427–1446, https://doi.org/10.5194/bg-22-1427-2025, https://doi.org/10.5194/bg-22-1427-2025, 2025
Short summary
Short summary
Soil organic carbon models are used to predict how soils affect the concentration of CO2 in the atmosphere. We show that equifinality – the phenomenon that different parameter values lead to correct overall model outputs, albeit with a different model behaviour – is an important source of model uncertainty. Our results imply that adding more complexity to soil organic carbon models is unlikely to lead to better predictions as long as more data to constrain model parameters are not available.
Mosisa Tujuba Wakjira, Nadav Peleg, Johan Six, and Peter Molnar
Hydrol. Earth Syst. Sci., 29, 863–886, https://doi.org/10.5194/hess-29-863-2025, https://doi.org/10.5194/hess-29-863-2025, 2025
Short summary
Short summary
In this study, we implement a climate, water, and crop interaction model to evaluate current conditions and project future changes in rainwater availability and its yield potential, with the goal of informing adaptation policies and strategies in Ethiopia. Although climate change is likely to increase rainfall in Ethiopia, our findings suggest that water-scarce croplands in Ethiopia are expected to face reduced crop yields during the main growing season due to increases in temperature.
Vira Leng, Rémi Cardinael, Florent Tivet, Vang Seng, Phearum Mark, Pascal Lienhard, Titouan Filloux, Johan Six, Lyda Hok, Stéphane Boulakia, Clever Briedis, João Carlos de Moraes Sá, and Laurent Thuriès
SOIL, 10, 699–725, https://doi.org/10.5194/soil-10-699-2024, https://doi.org/10.5194/soil-10-699-2024, 2024
Short summary
Short summary
We assessed the long-term impacts of no-till cropping systems on soil organic carbon and nitrogen dynamics down to 1 m depth under the annual upland crop productions (cassava, maize, and soybean) in the tropical climate of Cambodia. We showed that no-till systems combined with rotations and cover crops could store large amounts of carbon in the top and subsoil in both the mineral organic matter and particulate organic matter fractions. We also question nitrogen management in these systems.
Moritz Laub, Magdalena Necpalova, Marijn Van de Broek, Marc Corbeels, Samuel Mathu Ndungu, Monicah Wanjiku Mucheru-Muna, Daniel Mugendi, Rebecca Yegon, Wycliffe Waswa, Bernard Vanlauwe, and Johan Six
Biogeosciences, 21, 3691–3716, https://doi.org/10.5194/bg-21-3691-2024, https://doi.org/10.5194/bg-21-3691-2024, 2024
Short summary
Short summary
We used the DayCent model to assess the potential impact of integrated soil fertility management (ISFM) on maize production, soil fertility, and greenhouse gas emission in Kenya. After adjustments, DayCent represented measured mean yields and soil carbon stock changes well and N2O emissions acceptably. Our results showed that soil fertility losses could be reduced but not completely eliminated with ISFM and that, while N2O emissions increased with ISFM, emissions per kilogram yield decreased.
Claude Raoul Müller, Johan Six, Liesa Brosens, Philipp Baumann, Jean Paolo Gomes Minella, Gerard Govers, and Marijn Van de Broek
SOIL, 10, 349–365, https://doi.org/10.5194/soil-10-349-2024, https://doi.org/10.5194/soil-10-349-2024, 2024
Short summary
Short summary
Subsoils in the tropics are not as extensively studied as those in temperate regions. In this study, the conversion of forest to agriculture in a subtropical region affected the concentration of stabilized organic carbon (OC) down to 90 cm depth, while no significant differences between 90 cm and 300 cm were detected. Our results suggest that subsoils below 90 cm are unlikely to accumulate additional stabilized OC through reforestation over decadal periods due to declining OC input with depth.
Johan Six, Sebastian Doetterl, Moritz Laub, Claude R. Müller, and Marijn Van de Broek
SOIL, 10, 275–279, https://doi.org/10.5194/soil-10-275-2024, https://doi.org/10.5194/soil-10-275-2024, 2024
Short summary
Short summary
Soil C saturation has been tested in several recent studies and led to a debate about its existence. We argue that, to test C saturation, one should pay attention to six fundamental principles: the right measures, the right units, the right dispersive energy and application, the right soil type, the right clay type, and the right saturation level. Once we take care of those six rights across studies, we find support for a maximum of C stabilized by minerals and thus soil C saturation.
Armwell Shumba, Regis Chikowo, Christian Thierfelder, Marc Corbeels, Johan Six, and Rémi Cardinael
SOIL, 10, 151–165, https://doi.org/10.5194/soil-10-151-2024, https://doi.org/10.5194/soil-10-151-2024, 2024
Short summary
Short summary
Conservation agriculture (CA), combining reduced or no tillage, permanent soil cover, and improved rotations, is often promoted as a climate-smart practice. However, our knowledge of the impact of CA on top- and subsoil soil organic carbon (SOC) stocks in the low-input cropping systems of sub-Saharan Africa is rather limited. Using two long-term experimental sites with different soil types, we found that mulch could increase top SOC stocks, but no tillage alone had a slightly negative impact.
Moritz Laub, Sergey Blagodatsky, Marijn Van de Broek, Samuel Schlichenmaier, Benjapon Kunlanit, Johan Six, Patma Vityakon, and Georg Cadisch
Geosci. Model Dev., 17, 931–956, https://doi.org/10.5194/gmd-17-931-2024, https://doi.org/10.5194/gmd-17-931-2024, 2024
Short summary
Short summary
To manage soil organic matter (SOM) sustainably, we need a better understanding of the role that soil microbes play in aggregate protection. Here, we propose the SAMM model, which connects soil aggregate formation to microbial growth. We tested it against data from a tropical long-term experiment and show that SAMM effectively represents the microbial growth, SOM, and aggregate dynamics and that it can be used to explore the importance of aggregate formation in SOM stabilization.
Moritz Laub, Marc Corbeels, Antoine Couëdel, Samuel Mathu Ndungu, Monicah Wanjiku Mucheru-Muna, Daniel Mugendi, Magdalena Necpalova, Wycliffe Waswa, Marijn Van de Broek, Bernard Vanlauwe, and Johan Six
SOIL, 9, 301–323, https://doi.org/10.5194/soil-9-301-2023, https://doi.org/10.5194/soil-9-301-2023, 2023
Short summary
Short summary
In sub-Saharan Africa, long-term low-input maize cropping threatens soil fertility. We studied how different quality organic inputs combined with mineral N fertilizer could counteract this. Farmyard manure was the best input to counteract soil carbon loss; mineral N fertilizer had no effect on carbon. Yet, the rates needed to offset soil carbon losses are unrealistic for farmers (>10 t of dry matter per hectare and year). Additional agronomic measures may be needed.
Kristof Van Oost and Johan Six
Biogeosciences, 20, 635–646, https://doi.org/10.5194/bg-20-635-2023, https://doi.org/10.5194/bg-20-635-2023, 2023
Short summary
Short summary
The direction and magnitude of the net erosion-induced land–atmosphere C exchange have been the topic of a big scientific debate for more than a decade now. Many have assumed that erosion leads to a loss of soil carbon to the atmosphere, whereas others have shown that erosion ultimately leads to a carbon sink. Here, we show that the soil carbon erosion source–sink paradox is reconciled when the broad range of temporal and spatial scales at which the underlying processes operate are considered.
Charlotte Decock, Juhwan Lee, Matti Barthel, Elizabeth Verhoeven, Franz Conen, and Johan Six
Biogeosciences Discuss., https://doi.org/10.5194/bg-2022-221, https://doi.org/10.5194/bg-2022-221, 2022
Preprint withdrawn
Short summary
Short summary
One of the least well understood processes in the nitrogen (N) cycle is the loss of nitrogen gas (N2), referred to as total denitrification. This is mainly due to the difficulty of quantifying total denitrification in situ. In this study, we developed and tested a novel modeling approach to estimate total denitrification over the depth profile, based on concentrations and isotope values of N2O. Our method will help close N budgets and identify management strategies that reduce N pollution.
Tegawende Léa Jeanne Ilboudo, Lucien NGuessan Diby, Delwendé Innocent Kiba, Tor Gunnar Vågen, Leigh Ann Winowiecki, Hassan Bismarck Nacro, Johan Six, and Emmanuel Frossard
EGUsphere, https://doi.org/10.5194/egusphere-2022-209, https://doi.org/10.5194/egusphere-2022-209, 2022
Preprint withdrawn
Short summary
Short summary
Our results showed that at landscape level SOC stock variability was mainly explained by clay content. We found significant linear positive relationships between VC and SOC stocks for the land uses annual croplands, perennial croplands, grasslands and bushlands without soil depth restrictions until 110 cm. We concluded that in the forest-savanna transition zone, soil properties and topography determine land use, which in turn affects the stocks of SOC and TN and to some extent the VC stocks.
Rey Harvey Suello, Simon Lucas Hernandez, Steven Bouillon, Jean-Philippe Belliard, Luis Dominguez-Granda, Marijn Van de Broek, Andrea Mishell Rosado Moncayo, John Ramos Veliz, Karem Pollette Ramirez, Gerard Govers, and Stijn Temmerman
Biogeosciences, 19, 1571–1585, https://doi.org/10.5194/bg-19-1571-2022, https://doi.org/10.5194/bg-19-1571-2022, 2022
Short summary
Short summary
This research shows indications that the age of the mangrove forest and its position along a deltaic gradient (upstream–downstream) play a vital role in the amount and sources of carbon stored in the mangrove sediments. Our findings also imply that carbon capture by the mangrove ecosystem itself contributes partly but relatively little to long-term sediment organic carbon storage. This finding is particularly relevant for budgeting the potential of mangrove ecosystems to mitigate climate change.
Florian Lauryssen, Philippe Crombé, Tom Maris, Elliot Van Maldegem, Marijn Van de Broek, Stijn Temmerman, and Erik Smolders
Biogeosciences, 19, 763–776, https://doi.org/10.5194/bg-19-763-2022, https://doi.org/10.5194/bg-19-763-2022, 2022
Short summary
Short summary
Surface waters in lowland regions have a poor surface water quality, mainly due to excess nutrients like phosphate. Therefore, we wanted to know the phosphate levels without humans, also called the pre-industrial background. Phosphate binds strongly to sediment particles, suspended in the river water. In this research we used sediments deposited by a river as an archive for surface water phosphate back to 1800 CE. Pre-industrial phosphate levels were estimated at one-third of the modern levels.
Philipp Baumann, Juhwan Lee, Emmanuel Frossard, Laurie Paule Schönholzer, Lucien Diby, Valérie Kouamé Hgaza, Delwende Innocent Kiba, Andrew Sila, Keith Sheperd, and Johan Six
SOIL, 7, 717–731, https://doi.org/10.5194/soil-7-717-2021, https://doi.org/10.5194/soil-7-717-2021, 2021
Short summary
Short summary
This work delivers openly accessible and validated calibrations for diagnosing 26 soil properties based on mid-infrared spectroscopy. These were developed for four regions in Burkina Faso and Côte d'Ivoire, including 80 fields of smallholder farmers. The models can help to site-specifically and cost-efficiently monitor soil quality and fertility constraints to ameliorate soils and yields of yam or other staple crops in the four regions between the humid forest and the northern Guinean savanna.
Laura Summerauer, Philipp Baumann, Leonardo Ramirez-Lopez, Matti Barthel, Marijn Bauters, Benjamin Bukombe, Mario Reichenbach, Pascal Boeckx, Elizabeth Kearsley, Kristof Van Oost, Bernard Vanlauwe, Dieudonné Chiragaga, Aimé Bisimwa Heri-Kazi, Pieter Moonen, Andrew Sila, Keith Shepherd, Basile Bazirake Mujinya, Eric Van Ranst, Geert Baert, Sebastian Doetterl, and Johan Six
SOIL, 7, 693–715, https://doi.org/10.5194/soil-7-693-2021, https://doi.org/10.5194/soil-7-693-2021, 2021
Short summary
Short summary
We present a soil mid-infrared library with over 1800 samples from central Africa in order to facilitate soil analyses of this highly understudied yet critical area. Together with an existing continental library, we demonstrate a regional analysis and geographical extrapolation to predict total carbon and nitrogen. Our results show accurate predictions and highlight the value that the data contribute to existing libraries. Our library is openly available for public use and for expansion.
Sebastian Doetterl, Rodrigue K. Asifiwe, Geert Baert, Fernando Bamba, Marijn Bauters, Pascal Boeckx, Benjamin Bukombe, Georg Cadisch, Matthew Cooper, Landry N. Cizungu, Alison Hoyt, Clovis Kabaseke, Karsten Kalbitz, Laurent Kidinda, Annina Maier, Moritz Mainka, Julia Mayrock, Daniel Muhindo, Basile B. Mujinya, Serge M. Mukotanyi, Leon Nabahungu, Mario Reichenbach, Boris Rewald, Johan Six, Anna Stegmann, Laura Summerauer, Robin Unseld, Bernard Vanlauwe, Kristof Van Oost, Kris Verheyen, Cordula Vogel, Florian Wilken, and Peter Fiener
Earth Syst. Sci. Data, 13, 4133–4153, https://doi.org/10.5194/essd-13-4133-2021, https://doi.org/10.5194/essd-13-4133-2021, 2021
Short summary
Short summary
The African Tropics are hotspots of modern-day land use change and are of great relevance for the global carbon cycle. Here, we present data collected as part of the DFG-funded project TropSOC along topographic, land use, and geochemical gradients in the eastern Congo Basin and the Albertine Rift. Our database contains spatial and temporal data on soil, vegetation, environmental properties, and land management collected from 136 pristine tropical forest and cropland plots between 2017 and 2020.
Philipp Baumann, Anatol Helfenstein, Andreas Gubler, Armin Keller, Reto Giulio Meuli, Daniel Wächter, Juhwan Lee, Raphael Viscarra Rossel, and Johan Six
SOIL, 7, 525–546, https://doi.org/10.5194/soil-7-525-2021, https://doi.org/10.5194/soil-7-525-2021, 2021
Short summary
Short summary
We developed the Swiss mid-infrared spectral library and a statistical model collection across 4374 soil samples with reference measurements of 16 properties. Our library incorporates soil from 1094 grid locations and 71 long-term monitoring sites. This work confirms once again that nationwide spectral libraries with diverse soils can reliably feed information to a fast chemical diagnosis. Our data-driven reduction of the library has the potential to accurately monitor carbon at the plot scale.
Mario Reichenbach, Peter Fiener, Gina Garland, Marco Griepentrog, Johan Six, and Sebastian Doetterl
SOIL, 7, 453–475, https://doi.org/10.5194/soil-7-453-2021, https://doi.org/10.5194/soil-7-453-2021, 2021
Short summary
Short summary
In deeply weathered tropical rainforest soils of Africa, we found that patterns of soil organic carbon stocks differ between soils developed from geochemically contrasting parent material due to differences in the abundance of organo-mineral complexes, the presence/absence of chemical stabilization mechanisms of carbon with minerals and the presence of fossil organic carbon from sedimentary rocks. Physical stabilization mechanisms by aggregation provide additional protection of soil carbon.
Sophie F. von Fromm, Alison M. Hoyt, Markus Lange, Gifty E. Acquah, Ermias Aynekulu, Asmeret Asefaw Berhe, Stephan M. Haefele, Steve P. McGrath, Keith D. Shepherd, Andrew M. Sila, Johan Six, Erick K. Towett, Susan E. Trumbore, Tor-G. Vågen, Elvis Weullow, Leigh A. Winowiecki, and Sebastian Doetterl
SOIL, 7, 305–332, https://doi.org/10.5194/soil-7-305-2021, https://doi.org/10.5194/soil-7-305-2021, 2021
Short summary
Short summary
We investigated various soil and climate properties that influence soil organic carbon (SOC) concentrations in sub-Saharan Africa. Our findings indicate that climate and geochemistry are equally important for explaining SOC variations. The key SOC-controlling factors are broadly similar to those for temperate regions, despite differences in soil development history between the two regions.
Anatol Helfenstein, Philipp Baumann, Raphael Viscarra Rossel, Andreas Gubler, Stefan Oechslin, and Johan Six
SOIL, 7, 193–215, https://doi.org/10.5194/soil-7-193-2021, https://doi.org/10.5194/soil-7-193-2021, 2021
Short summary
Short summary
In this study, we show that a soil spectral library (SSL) can be used to predict soil carbon at new and very different locations. The importance of this finding is that it requires less time-consuming lab work than calibrating a new model for every local application, while still remaining similar to or more accurate than local models. Furthermore, we show that this method even works for predicting (drained) peat soils, using a SSL with mostly mineral soils containing much less soil carbon.
Simon Baumgartner, Marijn Bauters, Matti Barthel, Travis W. Drake, Landry C. Ntaboba, Basile M. Bazirake, Johan Six, Pascal Boeckx, and Kristof Van Oost
SOIL, 7, 83–94, https://doi.org/10.5194/soil-7-83-2021, https://doi.org/10.5194/soil-7-83-2021, 2021
Short summary
Short summary
We compared stable isotope signatures of soil profiles in different forest ecosystems within the Congo Basin to assess ecosystem-level differences in N cycling, and we examined the local effect of topography on the isotopic signature of soil N. Soil δ15N profiles indicated that the N cycling in in the montane forest is more closed, whereas the lowland forest and Miombo woodland experienced a more open N cycle. Topography only alters soil δ15N values in forests with high erosional forces.
Simon Baumgartner, Matti Barthel, Travis William Drake, Marijn Bauters, Isaac Ahanamungu Makelele, John Kalume Mugula, Laura Summerauer, Nora Gallarotti, Landry Cizungu Ntaboba, Kristof Van Oost, Pascal Boeckx, Sebastian Doetterl, Roland Anton Werner, and Johan Six
Biogeosciences, 17, 6207–6218, https://doi.org/10.5194/bg-17-6207-2020, https://doi.org/10.5194/bg-17-6207-2020, 2020
Short summary
Short summary
Soil respiration is an important carbon flux and key process determining the net ecosystem production of terrestrial ecosystems. The Congo Basin lacks studies quantifying carbon fluxes. We measured soil CO2 fluxes from different forest types in the Congo Basin and were able to show that, even though soil CO2 fluxes are similarly high in lowland and montane forests, the drivers were different: soil moisture in montane forests and C availability in the lowland forests.
Cited articles
Adams, A. M., Gillespie, A. W., Dhillon, G. S., Kar, G., Minielly, C., Koala, S., Ouattara, B., Kimaro, A. A., Bationo, A., Schoenau, J. J., and Peak, D.: Long-term effects of integrated soil fertility management practices on soil chemical properties in the Sahel, Geoderma, 366, 114207, https://doi.org/10.1016/j.geoderma.2020.114207, 2020.
Anandakumar, S., Bakhoum, N., Chinnadurai, C., Malarkodi, M., Arulmozhiselvan, K., Karthikeyan, S., and Balachandar, D.: Impact of long-term nutrient management on sequestration and dynamics of soil organic carbon in a semi-arid tropical Alfisol of India, Appl. Soil Ecol., 177, 104549, https://doi.org/10.1016/j.apsoil.2022.104549, 2022.
Balesdent, J., Mariotti, A., and Guillet, B.: Natural 13C abundance as a tracer for studies of soil organic matter dynamics, Soil Biol. Biochem., 19, 25–30, https://doi.org/10.1016/0038-0717(87)90120-9, 1987.
Balesdent, J., Basile-Doelsch, I., Chadoeuf, J., Cornu, S., Derrien, D., Fekiacova, Z., and Hatté, C.: Atmosphere–soil carbon transfer as a function of soil depth, Nature, 559, 599–602, https://doi.org/10.1038/s41586-018-0328-3, 2018.
Bossio, D. A., Cook-Patton, S. C., Ellis, P. W., Fargione, J., Sanderman, J., Smith, P., Wood, S., Zomer, R. J., Von Unger, M., Emmer, I. M., and Griscom, B. W.: The role of soil carbon in natural climate solutions, Nat. Sustain., 3, 391–398, https://doi.org/10.1038/s41893-020-0491-z, 2020.
Bullock, E. L., Healey, S. P., Yang, Z., Oduor, P., Gorelick, N., Omondi, S., Ouko, E., and Cohen, W. B.: Three Decades of Land Cover Change in East Africa, Land, 10, 150, https://doi.org/10.3390/land10020150, 2021.
Cardinael, R., Guibert, H., Brédoumy, S. T. K., Gigou, J., N'Goran, K. E., and Corbeels, M.: Sustaining maize yields and soil carbon following land clearing in the forest–savannah transition zone of West Africa: Results from a 20-year experiment, Field Crops Res., 275, 108335, https://doi.org/10.1016/j.fcr.2021.108335, 2022.
Champely, S.: pwr: Basic Functions for Power Analysis, https://doi.org/10.32614/CRAN.package.pwr, 2006.
Chen, R., Senbayram, M., Blagodatsky, S., Myachina, O., Dittert, K., Lin, X., Blagodatskaya, E., and Kuzyakov, Y.: Soil C and N availability determine the priming effect: microbial N mining and stoichiometric decomposition theories, Glob. Change Biol., 20, 2356–2367, https://doi.org/10.1111/gcb.12475, 2014.
Chen, Y. and Aviad, T.: Effects of Humic Substances on Plant Growth, in: Humic Substances in Soil and Crop Sciences: Selected Readings, edited by: MacCarthy, P., Clapp, C. E., Malcolm, R. L., and Bloom, P. R., Soil Science Society of America, Madison, WI, USA, 161–186, https://doi.org/10.2136/1990.humicsubstances.c7, 1990.
Chivenge, P., Vanlauwe, B., Gentile, R., Wangechi, H., Mugendi, D., van Kessel, C., and Six, J.: Organic and Mineral Input Management to Enhance Crop Productivity in Central Kenya, Agron. J., 101, 1266–1275, https://doi.org/10.2134/agronj2008.0188x, 2009.
Chivenge, P., Vanlauwe, B., Gentile, R., and Six, J.: Comparison of organic versus mineral resource effects on short-term aggregate carbon and nitrogen dynamics in a sandy soil versus a fine textured soil, Agr. Ecosyst. Environ., 140, 361–371, https://doi.org/10.1016/j.agee.2010.12.004, 2011a.
Chivenge, P., Vanlauwe, B., and Six, J.: Does the combined application of organic and mineral nutrient sources influence maize productivity? A meta-analysis, Plant Soil, 342, 1–30, https://doi.org/10.1007/s11104-010-0626-5, 2011b.
Corbeels, M., Cardinael, R., Naudin, K., Guibert, H., and Torquebiau, E.: The 4 per 1000 goal and soil carbon storage under agroforestry and conservation agriculture systems in sub-Saharan Africa, Soil Till. Res., 188, 16–26, https://doi.org/10.1016/j.still.2018.02.015, 2019.
Córdova, S. C., Olk, D. C., Dietzel, R. N., Mueller, K. E., Archontouilis, S. V., and Castellano, M. J.: Plant litter quality affects the accumulation rate, composition, and stability of mineral-associated soil organic matter, Soil Biol. Biochem., 125, 115–124, https://doi.org/10.1016/j.soilbio.2018.07.010, 2018.
Ehleringer, J. R., Buchmann, N., and Flanagan, L. B.: Carbon Isotope Ratios in belowground carbon cycle processes, Ecol. Appl., 10, 412–422, https://doi.org/10.1890/1051-0761(2000)010[0412:CIRIBC]2.0.CO;2, 2000.
Farquhar, G. D., Ehleringer, J. R., and Hubick, K. T.: Carbon isotope discrimination and photosynthesis, Annu. Rev. Plant Phys., 40, 503–537, https://doi.org/10.1146/annurev.arplant.40.1.503, 1989.
Feller, C. and Beare, M. H.: Physical control of soil organic matter dynamics in the tropics, Geoderma, 79, 69–116, https://doi.org/10.1016/S0016-7061(97)00039-6, 1997.
Fujisaki, K., Chevallier, T., Chapuis-Lardy, L., Albrecht, A., Razafimbelo, T., Masse, D., Ndour, Y. B., and Chotte, J.-L.: Soil carbon stock changes in tropical croplands are mainly driven by carbon inputs: A synthesis, Agr. Ecosyst. Environ., 259, 147–158, https://doi.org/10.1016/j.agee.2017.12.008, 2018.
Geisseler, D. and Scow, K. M.: Long-term effects of mineral fertilizers on soil microorganisms – A review, Soil Biol. Biochem., 75, 54–63, https://doi.org/10.1016/j.soilbio.2014.03.023, 2014.
Gentile, R., Vanlauwe, B., Chivenge, P., and Six, J.: Interactive effects from combining fertilizer and organic residue inputs on nitrogen transformations, Soil Biol. Biochem., 40, 2375–2384, https://doi.org/10.1016/j.soilbio.2008.05.018, 2008.
Gentile, R., Vanlauwe, B., and Six, J.: Litter quality impacts short- but not long-term soil carbon dynamics in soil aggregate fractions, Ecol. Appl., 21, 695–703, https://doi.org/10.1890/09-2325.1, 2011.
Gram, G., Roobroeck, D., Pypers, P., Six, J., Merckx, R., and Vanlauwe, B.: Combining organic and mineral fertilizers as a climate-smart integrated soil fertility management practice in sub-Saharan Africa: A meta-analysis, PLoS ONE, 15, e0239552, https://doi.org/10.1371/journal.pone.0239552, 2020.
Greenwood, D. J., Gerwitz, A., Stone, D. A., and Barnes, A.: Root development of vegetable crops, Plant and Soil, 68, 75–96, https://www.jstor.org/stable/42934072 (last access: 5 August 2024), 1982.
Gross, A. and Glaser, B.: Meta-analysis on how manure application changes soil organic carbon storage, Sci. Rep., 11, 5516, https://doi.org/10.1038/s41598-021-82739-7, 2021.
Hansen, M. C., Potapov, P. V., Moore, R., Hancher, M., Turubanova, S. A., Tyukavina, A., Thau, D., Stehman, S. V., Goetz, S. J., Loveland, T. R., Kommareddy, A., Egorov, A., Chini, L., Justice, C. O., and Townshend, J. R. G.: High-Resolution Global Maps of 21st-Century Forest Cover Change, Science, 342, 850–853, https://doi.org/10.1126/science.1244693, 2013.
Hendershot, W. H. and Duquette, M.: A Simple Barium Chloride Method for Determining Cation Exchange Capacity and Exchangeable Cations, Soil Sci. Soc. Am. J., 50, 605–608, https://doi.org/10.2136/sssaj1986.03615995005000030013x, 1986.
Hofmann, A., Heim, A., Gioacchini, P., Miltner, A., Gehre, M., and Schmidt, M. W. I.: Mineral fertilization did not affect decay of old lignin and SOC in a 13C-labeled arable soil over 36 years, Biogeosciences, 6, 1139–1148, https://doi.org/10.5194/bg-6-1139-2009, 2009.
Kaiser, K. and Kalbitz, K.: Cycling downwards – dissolved organic matter in soils, Soil Biol. Biochem., 52, 29–32, https://doi.org/10.1016/j.soilbio.2012.04.002, 2012a.
Kaiser, K. and Kalbitz, K.: Cycling downwards – dissolved organic matter in soils, Soil Biol. Biochem., 52, 29–32, https://doi.org/10.1016/j.soilbio.2012.04.002, 2012b.
Kassambara, A.: rstatix: Pipe-Friendly Framework for Basic Statistical Tests, R package version 0.7.1, https://CRAN.R-project.org/package=rstatix (last access: 5 August 2024), 2022.
Kihara, J., Bolo, P., Kinyua, M., Nyawira, S. S., and Sommer, R.: Soil health and ecosystem services: Lessons from sub-Sahara Africa (SSA), Geoderma, 370, 114342, https://doi.org/10.1016/j.geoderma.2020.114342, 2020.
Komada, T., Anderson, M. R., and Dorfmeier, C. L.: Carbonate removal from coastal sediments for the determination of organic carbon and its isotopic signatures, δ13C and Δ14C: comparison of fumigation and direct acidification by hydrochloric acid, Limnol. Ocean Method., 6, 254–262, https://doi.org/10.4319/lom.2008.6.254, 2008.
Kuznetsova, A., Brockhoff, P. B., and Christensen, R. H. B.: lmerTes Package: Tests in Linear Mixed Effects Models, J. Stat. Soft., 82, 1–26, https://doi.org/10.18637/jss.v082.i13, 2017.
Ladha, J. K., Reddy, C. K., Padre, A. T., and Van Kessel, C.: Role of Nitrogen Fertilization in Sustaining Organic Matter in Cultivated Soils, J. Environ. Qual., 40, 1756–1766, https://doi.org/10.2134/jeq2011.0064, 2011.
Lal, R.: Soils and sustainable agriculture, A review, Agron. Sustain. Dev., 28, 57–64, https://doi.org/10.1051/agro:2007025, 2008.
Lal, R.: Digging deeper: A holistic perspective of factors affecting soil organic carbon sequestration in agroecosystems, Glob. Change Biol., 24, 3285–3301, https://doi.org/10.1111/gcb.14054, 2018.
Laub, M., Schlichenmeier, S., Vityakon, P., and Cadisch, G.: Litter Quality and Microbes Explain Aggregation Differences in a Tropical Sandy Soil, J. Soil Sci. Plant Nutr., 22, 848–860, https://doi.org/10.1007/s42729-021-00696-6, 2022.
Laub, M., Corbeels, M., Mathu Ndungu, S., Mucheru-Muna, M. W., Mugendi, D., Necpalova, M., Van De Broek, M., Waswa, W., Vanlauwe, B., and Six, J.: Combining manure with mineral N fertilizer maintains maize yields: Evidence from four long-term experiments in Kenya, Field Crops Res., 291, 108788, https://doi.org/10.1016/j.fcr.2022.108788, 2023a.
Laub, M., Corbeels, M., Couëdel, A., Ndungu, S. M., Mucheru-Muna, M. W., Mugendi, D., Necpalova, M., Waswa, W., Van de Broek, M., Vanlauwe, B., and Six, J.: Managing soil organic carbon in tropical agroecosystems: evidence from four long-term experiments in Kenya, SOIL, 9, 301–323, https://doi.org/10.5194/soil-9-301-2023, 2023b.
Leuther, F., Wolff, M., Kaiser, K., Schumann, L., Merbach, I., Mikutta, R., and Schlüter, S.: Response of subsoil organic matter contents and physical properties to long-term, high-rate farmyard manure application, Europ. J. Soil Sci., 73, e13233, https://doi.org/10.1111/ejss.13233, 2022.
Liu, E., Yan, C., Mei, X., Zhang, Y., and Fan, T.: Long-Term Effect of Manure and Fertilizer on Soil Organic Carbon Pools in Dryland Farming in Northwest China, PLoS ONE, 8, e56536, https://doi.org/10.1371/journal.pone.0056536, 2013.
Liu, N., Li, Y., Cong, P., Wang, J., Guo, W., Pang, H., and Zhang, L.: Depth of straw incorporation significantly alters crop yield, soil organic carbon and total nitrogen in the North China Plain, Soil Till. Res., 205, 104772, https://doi.org/10.1016/j.still.2020.104772, 2021.
Liu, Y., Li, C., Cai, G., Sauheitl, L., Xiao, M., Shibistova, O., Ge, T., and Guggenberger, G.: Meta-analysis on the effects of types and levels of N, P, and K fertilization on organic carbon in cropland soils, Geoderma, 437, 116580, https://doi.org/10.1016/j.geoderma.2023.116580, 2023.
Ma, Q., Bell, R. W., and Mattiello, E. M.: Nutrient Acquisition with Particular Reference to Subsoil Constraints, in: Subsoil Constraints for Crop Production, edited by: Oliveira, T. S. D. and Bell, R. W., Springer International Publishing, Cham, 289–321, https://doi.org/10.1007/978-3-031-00317-2_12, 2022.
Mathieu, J. A., Hatté, C., Balesdent, J., and Parent, É.: Deep soil carbon dynamics are driven more by soil type than by climate: a worldwide meta-analysis of radiocarbon profiles, Glob. Change Biol., 21, 4278–4292, https://doi.org/10.1111/gcb.13012, 2015.
Minasny, B., Malone, B. P., McBratney, A. B., Angers, D. A., Arrouays, D., Chambers, A., Chaplot, V., Chen, Z.-S., Cheng, K., Das, B. S., Field, D. J., Gimona, A., Hedley, C. B., Hong, S. Y., Mandal, B., Marchant, B. P., Martin, M., McConkey, B. G., Mulder, V. L., O'Rourke, S., Richer-de-Forges, A. C., Odeh, I., Padarian, J., Paustian, K., Pan, G., Poggio, L., Savin, I., Stolbovoy, V., Stockmann, U., Sulaeman, Y., Tsui, C.-C., Vågen, T.-G., Van Wesemael, B., and Winowiecki, L.: Soil carbon 4 per mille, Geoderma, 292, 59–86, https://doi.org/10.1016/j.geoderma.2017.01.002, 2017.
Müller, C. R.: EmbuPub_SOC, Figshare [date set], https://figshare.com/s/c2f2787b7a56ef7ad656, last access: 20 April 2025.
Ndung'u, M., Ngatia, L. W., Onwonga, R. N., Mucheru-Muna, M. W., Fu, R., Moriasi, D. N., and Ngetich, K. F.: The influence of organic and inorganic nutrient inputs on soil organic carbon functional groups content and maize yields, Heliyon, 7, e07881, https://doi.org/10.1016/j.heliyon.2021.e07881, 2021.
Pretty, J.: Sustainable intensification in Africa, Int. J. Agr. Sustain., 9, 3–4, https://doi.org/10.3763/ijas.2011.91ED, 2011.
Reimer, P., Brown, T., and Reimer, R.: Discussion: Reporting and Calibration of Post-Bomb 14C Data, Radiocarbon, 46, 1299–1304, https://doi.org/10.1017/S0033822200033154, 2004.
Rumpel, C. and Kögel-Knabner, I.: Deep soil organic matter—a key but poorly understood component of terrestrial C cycle, Plant Soil, 338, 143–158, https://doi.org/10.1007/s11104-010-0391-5, 2011.
Shumba, A., Chikowo, R., Thierfelder, C., Corbeels, M., Six, J., and Cardinael, R.: Mulch application as the overarching factor explaining increase in soil organic carbon stocks under conservation agriculture in two 8-year-old experiments in Zimbabwe, SOIL, 10, 151–165, https://doi.org/10.5194/soil-10-151-2024, 2024.
Sierra, C. A., Ahrens, B., Bolinder, M. A., Braakhekke, M. C., Von Fromm, S., Kätterer, T., Luo, Z., Parvin, N., and Wang, G.: Carbon sequestration in the subsoil and the time required to stabilize carbon for climate change mitigation, Glob. Change Biol., 30, e17153, https://doi.org/10.1111/gcb.17153, 2024.
Six, J., Feller, C., Denef, K., Ogle, S. M., de Moraes, J. C., and Albrecht, A.: Soil organic matter, biota and aggregation in temperateand tropical soils - Effects of no-tillage, Agronomie, 22, 755–775, https://doi.org/10.1051/agro:2002043, 2002.
Sommer, R., Paul, B. K., Mukalama, J., and Kihara, J.: Reducing losses but failing to sequester carbon in soils – the case of Conservation Agriculture and Integrated Soil Fertility Management in the humid tropical agro-ecosystem of Western Kenya, Agr. Ecosyst. Environ., 254, 82–91, https://doi.org/10.1016/j.agee.2017.11.004, 2018.
Stuiver, M. and Polach, H. A.: Discussion reporting of 14C data, Radiocarbon, 19, 355–363, 1977.
Tardieu, F.: Analysis of the spatial variability of maize root density, Plant and Soil, 107, 259–266, https://doi.org/10.1007/BF02370555, 1988.
Tieszen, L. L.: Natural variations in the carbon isotope values of plants: Implications for archaeology, ecology, and paleoecology, J. Archaeol. Sci., 18, 227–248, https://doi.org/10.1016/0305-4403(91)90063-U, 1991.
Tittonell, P., Corbeels, M., Van Wijk, M. T., Vanlauwe, B., and Giller, K. E.: Combining Organic and Mineral Fertilizers for Integrated Soil Fertility Management in Smallholder Farming Systems of Kenya: Explorations Using the Crop-Soil Model FIELD, Agron. J., 100, 1511–1526, https://doi.org/10.2134/agronj2007.0355, 2008.
Trevisan, S., Francioso, O., Quaggiotti, S., and Nardi, S.: Humic substances biological activity at the plant-soil interface: From environmental aspects to molecular factors, Plant Signal. Behav., 5, 635–643, https://doi.org/10.4161/psb.5.6.11211, 2010.
Trumbore, S. E., Vogel, J. S., and Southon, J. R.: AMS 14C Measurements of Fractionated Soil Organic Matter: An Approach to Deciphering the Soil Carbon Cycle, Radiocarbon, 31, 644–654, https://doi.org/10.1017/S0033822200012248, 1989.
Uselman, S. M., Qualls, R. G., and Lilienfein, J.: Contribution of Root vs. Leaf Litter to Dissolved Organic Carbon Leaching through Soil, Soil Sci. Soc. Am. J., 71, 1555–1563, https://doi.org/10.2136/sssaj2006.0386, 2007.
Van de Broek, M., Ghiasi, S., Decock, C., Hund, A., Abiven, S., Friedli, C., Werner, R. A., and Six, J.: The soil organic carbon stabilization potential of old and new wheat cultivars: a 13CO2-labeling study, Biogeosciences, 17, 2971–2986, https://doi.org/10.5194/bg-17-2971-2020, 2020.
Vanlauwe, B. and Giller, K.: Popular myths around soil fertility management in sub-Saharan Africa, Agr. Ecosyst. Environ., 116, 34–46, https://doi.org/10.1016/j.agee.2006.03.016, 2006.
Vanlauwe, B., Gachengo, C., Shepherd, K., Barrios, E., Cadisch, G., and Palm, C. A.: Laboratory Validation of a Resource Quality-Based Conceptual Framework for Organic Matter Management, Soil Sci. Soc. Am. j., 69, 1135–1145, https://doi.org/10.2136/sssaj2004.0089, 2005.
Vanlauwe, B., Chianu, J., Giller, K. E., Merckx, R., Mokwunye, U., Pypers, P., Shepherd, K., Woomer, P. L., and Sanginga, N.: Integrated soil fertility management: operational definition and consequences for implementation and dissemination, Outlook Agr., 39, 17–24, https://doi.org/10.5367/000000010791169998, 2010.
Vanlauwe, B., Descheemaeker, K., Giller, K. E., Huising, J., Merckx, R., Nziguheba, G., Wendt, J., and Zingore, S.: Integrated soil fertility management in sub-Saharan Africa: unravelling local adaptation, SOIL, 1, 491–508, https://doi.org/10.5194/soil-1-491-2015, 2015.
Veldkamp, E., Schmidt, M., Powers, J. S., and Corre, M. D.: Deforestation and reforestation impacts on soils in the tropics, Nat. Rev. Earth Environ., 1, 590–605, https://doi.org/10.1038/s43017-020-0091-5, 2020.
Wang, J., Sun, J., Xia, J., He, N., Li, M., and Niu, S.: Soil and vegetation carbon turnover times from tropical to boreal forests, Funct. Ecol., 32, 71–82, https://doi.org/10.1111/1365-2435.12914, 2018.
Wiesmeier, M., Urbanski, L., Hobley, E., Lang, B., von Lützow, M., Marin-Spiotta, E., van Wesemael, B., Rabot, E., Ließ, M., Garcia-Franco, N., Wollschläger, U., Vogel, H.-J., and Kögel-Knabner, I.: Soil organic carbon storage as a key function of soils – A review of drivers and indicators at various scales, Geoderma, 333, 149–162, https://doi.org/10.1016/j.geoderma.2018.07.026, 2019.
Yang, X., Xiong, J., Du, T., Ju, X., Gan, Y., Li, S., Xia, L., Shen, Y., Pacenka, S., Steenhuis, T. S., Siddique, K. H. M., Kang, S., and Butterbach-Bahl, K.: Diversifying crop rotation increases food production, reduces net greenhouse gas emissions and improves soil health, Nat. Commun., 15, 198, https://doi.org/10.1038/s41467-023-44464-9, 2024.
Yost, J. L. and Hartemink, A. E.: How deep is the soil studied – an analysis of four soil science journals, Plant Soil, 452, 5–18, https://doi.org/10.1007/s11104-020-04550-z, 2020.
Short summary
We studied how different organic and inorganic nutrient inputs affect soil organic carbon (SOC) down to 70 cm in Kenya. After 19 years, all organic treatments increased SOC stocks compared with the control, but mineral nitrogen had no significant effect. Manure was the organic treatment that significantly increased SOC at the deepest soil depths, as its effect could be observed down to 60 cm. Manure was the best strategy to limit SOC loss in croplands and maintain soil quality after deforestation.
We studied how different organic and inorganic nutrient inputs affect soil organic carbon (SOC)...
Altmetrics
Final-revised paper
Preprint