Soil organic carbon and nitrogen dynamics under long-term conservation agriculture systems in Cambodia

Leng Vira, Cardinael Rémi, Seng Vang, Tivet Florent, Lienhard Pascal, Mark Phearum, Six Johan, Hok Lyda, Boulakia Stéphane, Thuriès Laurent. 2023. Soil organic carbon and nitrogen dynamics under long-term conservation agriculture systems in Cambodia. In : Long Term Experiments: meeting future challenges. AAB. Rothamsted : AAB, Résumé, 1 p. Long Term Experiments: Meeting Future Challenges, Rothamsted, Royaume-Uni, 20 Juin 2023/22 Juin 2023.

Résumé : This study quantified soil organic carbon (SOC) and soil total nitrogen (STN) changes in three long-term (14 years) experiments comparing conventional tillage (CT) and different no-till (NT) cropping systems using a diachronic approach and an equivalent soil mass approach. The three experiments were established in 2009 in a randomized complete block design with three replicates and comprise maize (MaiEx)-, soybean (SoyEx)-, and cassava (CasEx)-based cropping systems. Soil samples were collected in 2021, 10 years after the first sampling (2011), at 7 depths: 0–5, 5–10, 10–20, 20–40, 40–60, 60–80, and 80–100 cm. At 0–10 cm depth, NTs significantly increased SOC stock at a rate of 0.35, 0.51 and 0.73 Mg C ha-1 y-1 for CasEx, SoyEx and MaiEx, respectively. CT exhibited a positive trend only on CasEx with an accumulation rate of 0.14 Mg C ha-1 y-1 (0-10 cm). A significant SOC accumulation was observed under NT cropping systems for CasEX and MaiEx up to 60-80 and 80-100 cm depth, respectively. By contrast, STN stock significantly increased under NT cropping systems only at 0–5 cm depth with an accumulation rate of 13.9, 22.9 and 34.0 kg N ha-1 y-1 under CasEx, SoyEx and MaiEx, respectively. A depletion of N stocks was observed under CT and NT cropping systems at deeper soil layers. Over 10 years of time, SOC accumulation rate of NT, at 0-100 cm depth, reached 1.08 and 1.73 Mg C ha-1 yr-1 for CasEx and MaiEx, respectively while non-significant change was observed under NT SoyEx and CT of the three experiments. The findings suggest that long-term NT cropping systems with high amount of biomass-C inputs and crop rotation enhance SOC sequestration even at deeper soil layers. However, these results raise questions about the dynamics of N under NT cropping systems.

Mots-clés libres : Conservation agriculture, Soil organic carbon, Cassava, Climate change mitigation, No till

Auteurs et affiliations

• Leng Vira
• Cardinael Rémi, CIRAD-PERSYST-UPR AIDA (ZWE) ORCID: 0000-0002-9924-3269
• Seng Vang, Ministry of Agriculture, Forestry and Fisheries (Cambodge) (KHM)
• Tivet Florent, CIRAD-PERSYST-UPR AIDA (KHM)
• Lienhard Pascal, CIRAD-PERSYST-UPR AIDA (VNM)
• Mark Phearum, Ministry of Agriculture, Forestry and Fisheries (Cambodge) (KHM)
• Six Johan, ETH (CHE)
• Hok Lyda, Royal University of Agriculture (KHM)
• Boulakia Stéphane, CIRAD-PERSYST-UPR AIDA (FRA) ORCID: 0000-0003-4331-1207
• Thuriès Laurent, CIRAD-PERSYST-UPR Recyclage et risque (FRA) ORCID: 0000-0002-1365-7891

Source : Cirad-Agritrop (https://agritrop.cirad.fr/605171/)

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