Soil organic carbon stocks and greenhouse gas emissions in two long-term conservation agriculture experiments in sub-humid Zimbabwe

Shumba Armwell, Chikowo Régis, Thierfelder Christian, Corbeels Marc, Six Johan, Cardinael Rémi. 2023. Soil organic carbon stocks and greenhouse gas emissions in two long-term conservation agriculture experiments in sub-humid Zimbabwe. . AAB. Rothamsted : AAB, 2 p. Long Term Experiments: Meeting Future Challenges, Rothamsted, Royaume-Uni, 20 Juin 2023/22 Juin 2023.

Résumé : Soils store significant amounts of carbon (C) and play a critical role in mitigating climate change through C sequestration. This study evaluated the potential contribution of each conservation agriculture (CA) principle or their different combinations to soil C stock and greenhouse gas emissions. A CA component emission experiment was established in 2013 in Zimbabwe on an abruptic Lixisol (DTC site) and a xanthic Ferralsol (UZF site). The main crop was maize (Zea mays L.) and treatments with rotation included cowpea (Vigna unguiculate L. Walp.). Gas samples were regularly collected using the static chamber method in the maize rows and inter-rows during the 2019/20 and 2020/21 seasons. In 2021, soil samples for SOC were taken down to 1 m soil depth and SOC stocks were calculated using the equivalent soil mass approach. In the 2019/20 cropping season, cumulative N2O-N emissions were significantly higher in mulch and cowpea rotation treatments at DTC and UZF, respectively and ranged from 215 to 496 g and 226 to 395 g N2O-N ha−1 yr−1. There were no significant differences in yield-scaled N2O emissions between treatments at both sites for the two seasons. Cumulative CO2-C efflux was not significantly different between treatments, but it was significantly higher in the rows than in the inter-rows. Significantly higher cumulative SOC stocks were found within the top 20 cm at DTC and UZF in the no-tillage plus mulch (NTM) treatment compared to no tillage (NT) and conventional tillage (CT). SOC accumulation rate was highest in NTM (0.30 and 0.26 Mg C ha-1 year-1 at DTC and UZF, respectively) compared to CT. Overall, the study showed generally low greenhouse gas emissions but a potential trade-off between additional SOC storage and N2O emissions in the mulch and rotation treatments.

Mots-clés libres : Conservation agriculture, Greenhouse Gases, Soilr organic carbon, Climate change mitigation

Auteurs et affiliations

• Shumba Armwell, University of Zimbabwe (ZWE)
• Chikowo Régis, University of Zimbabwe (ZWE)
• Thierfelder Christian, CIMMYT (ZWE)
• Corbeels Marc, CIRAD-PERSYST-UPR AIDA (KEN) ORCID: 0000-0002-8084-9287
• Six Johan, ETH (CHE)
• Cardinael Rémi, CIRAD-PERSYST-UPR AIDA (ZWE) ORCID: 0000-0002-9924-3269

Source : Cirad-Agritrop (https://agritrop.cirad.fr/605169/)

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