EGUsphere

Copernicus Publications

Göttingen, Germany

10.5194/egusphere-2023-1233

Conservation agriculture increases soil organic carbon stocks but not soil CO2 efflux in two 8-year-old experiments in Zimbabwe

Shumba

Armwell

https://orcid.org/0000-0002-7842-1492

¹ ² ³ Chikowo

Regis

¹ ⁴ Thierfelder

Christian

⁵ Corbeels

Marc

⁶ ⁷ Six

Johan

https://orcid.org/0000-0001-9336-4185

⁸ Cardinael

Rémi

https://orcid.org/0000-0002-9924-3269

¹ ² ⁶

Department of Plant Production Sciences and Technologies, University of Zimbabwe, Harare, Zimbabwe

CIRAD, UPR AIDA, Harare, Zimbabwe

Fertilizer, Farm Feeds and Remedies Institute, Department of Research and Specialist Services, Ministry of Lands, Agriculture, Fisheries, Water and Rural Development, Harare, Zimbabwe

Plant, Soil and Microbial Sciences Department, Michigan State University, East Lansing, MI 48824, USA

International Maize and Wheat Improvement Center (CIMMYT), P.O. Box MP 163, Mount Pleasant, Harare, Zimbabwe

AIDA, Univ Montpellier, CIRAD, Montpellier, France

IITA, International Institute of Tropical Agriculture, PO Box 30772, Nairobi, 00100, Kenya

Department of Environmental Systems Science, ETH Zurich, 8092 Zürich, Switzerland

Agropolis Fondation

AF 1802-001

Total Foundation

C002181

20 07 2023

2023 1 40

2023

This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/

This article is available from https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1233/

The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1233/egusphere-2023-1233.pdf

Conservation agriculture (CA), combining reduced or no tillage, permanent soil cover and improved rotations, is often promoted as a climate-smart practice. However, our understanding about the impact of CA and its respective three principles on top and sub-soil organic carbon (SOC) stocks and on soil CO2 efflux in low input cropping systems of sub-Saharan Africa is rather limited. The study was conducted at two long-term experimental sites established in 2013 in Zimbabwe. The soil types were abruptic Lixisols at Domboshava Training Centre (DTC) and xanthic Ferralsol at the University of Zimbabwe farm (UZF). Six treatments, replicated four times were investigated: conventional tillage (CT), conventional tillage with rotation (CTR), NT, no-tillage with mulch (NTM), no-tillage with rotation (NTR), no-tillage with mulch and rotation (NTMR). Maize (Zea mays L.) was the main crop and treatments with rotation included cowpea (Vigna unguiculata L. Walp.). SOC concentration and bulk density were determined for samples taken from the 0–5, 5–10, 10–15, 15–20, 20–30, 30–40, 40–50, 50–75 and 75–100 cm depths. Gas samples were regularly collected using the static chamber method during the 2019/20 and 2020/21 cropping seasons and during the 2020/21 dry season. SOC stocks were significantly (p < 0.05) higher under NTM, NTR and NTMR compared to NT and CT in top 5 and 10 cm layers at UZF, while SOC stocks were only significantly higher under NTM and NTMR compared to NT and CT in top 5 cm at DTC. NT alone had a slightly negative impact on top SOC stock. Cumulative SOC stocks were not significantly different between treatments when considering the whole 100 cm soil profile. Regardless of larger organic carbon inputs in mulch treatments, there were no significant differences in CO2 efflux between treatments, but it was higher in maize rows than in inter-rows as a result of autotrophic respiration from maize roots. Our results show the overarching role of crop residue mulching in CA cropping systems in enhancing SOC storage but that this effect is limited to the topsoil.