Macroaggregation and soil organic carbon restoration in a highly weathered Brazilian Oxisol after two decades under no-till

De Oliveira Ferreira Ademir, De Moraes Sa Joao Carlos, Lal Rattan, Tivet Florent, Briedis Clever, Massao Inagaki Thiago, Potma Gonçalves Daniel Ruiz, Romaniw Jucimare. 2018. Macroaggregation and soil organic carbon restoration in a highly weathered Brazilian Oxisol after two decades under no-till. Science of the Total Environment, 621 : 1559-1567.

https://doi.org/10.1016/j.scitotenv.2017.10.072

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Quartile : Q1, Sujet : ENVIRONMENTAL SCIENCES

Résumé : Conclusions based on studies of the impacts of soil organic carbon (SOC) fractions and soil texture on macroaggregation and SOC stabilization in long-term (> 20 years) no-till (NT) fields remain debatable. This study was based on the hypothesis that the amount and frequency of biomass-C input associated with NT can be a pathway to formation of macroaggregates and to SOC buildup. The objectives were to: 1) assess the macroaggregate distribution (proportional mass, class mass) and the SOC and particulate organic carbon (POC) stocks of extra-large (8–19 mm), large (2–8 mm) and small (0.25–2 mm) macroaggregate size classes managed for two decades by NT, and 2) assess the recovery of SOC stocks in extra-large macroaggregates compared to adjacent native vegetation (Andropogon sp., Aristida sp., Paspalum sp., and Panicum sp.). The crop rotation systems were: soybean (Glycine max L.), maize (Zea mays L.) and beans (Phaseolus vulgaris L.) in summer; and black oat (Avena strigosa Schreb), white oat (Avena sativa), vetch (Vicia sativa L.), black oat. + vetch (Avena strigosa Schreb + vetch) and wheat (Triticum aestivum L.) in winter. The experimental was laid out as 2 × 2 randomized block factorial with 12 replicates of a NT experiment established in 1997 on two highly weathered Oxisols. The factors comprised of: (a) two soil textural types: clay loam and sandy clay, and (b) two sampling depths: 0–5 and 5–20 cm. The three classes of macroaggregates were obtained by wet sieving, and the SOC content was determined by the dry combustion method. The extra-large macroaggregate classes in 0–20 cm depth for sandy clay (SdC) and clay loam (CL) Oxisol represented 75.2 and 72.4% of proportional mass, respectively. The SOC and POC stocks among macroaggregate classes in 0–5 and 5–20 cm depths decreased in the order: 8–19 mm > 2–8 mm ≈ 0.25–2 mm. The SdC plots under soybean/maize at 3:1 ratio recovered 58.3%, while those at 1:1 ratio (high maize frequency) in CL recovered 73.1% of SOC stock in the extra-large macroaggregates compared with the same under native vegetation for 0–20 cm depth. Thus, partial restoration of the SOC stock in original extra-large macroaggregate confirms the hypothesis that NT through higher maize cultivation frequency can be a pathway to fomation of macroaggregates and SOC buildup.

Mots-clés Agrovoc : sol tropical, texture du sol, récupération des sols, matière organique du sol, teneur en matière organique, travail du sol, non-travail du sol, séquestration du carbone, modèle mathématique

Mots-clés géographiques Agrovoc : Brésil, Parana

Classification Agris : P33 - Chimie et physique du sol
P36 - Érosion, conservation et récupération des sols
F07 - Façons culturales
F08 - Systèmes et modes de culture
U10 - Informatique, mathématiques et statistiques

Champ stratégique Cirad : Axe 1 (2014-2018) - Agriculture écologiquement intensive

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