Aggregate C depletion by plowing and its restoration by diverse biomass-C inputs under no-till in sub-tropical and tropical regions of Brazil

• Published in: Soil & tillage research Vol. 126; pp. 203 - 218
• Main Authors: Tivet, Florent, de Moraes Sá, João Carlos, Lal, Rattan, Briedis, Clever, Borszowskei, Paulo Rogério, dos Santos, Josiane Bürkner, Farias, Anderson, Eurich, Guilherme, Hartman, Daiani da Cruz, Nadolny Junior, Mario, Bouzinac, Serge, Séguy, Lucien
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.2013; Elsevier
• Subjects: Aggregate hierarchy; Aggregate-C pathway; Agronomy. Soil science and plant productions; Biological and medical sciences; Biomass-C input; Chemical, physicochemical, biochemical and biological properties; Cropping systems. Cultivation. Soil tillage; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Labile fractions; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil organic carbon; Soil science; Soil tillage; Tillage. Tending. Growth control; South America; Brazil; America; Brazil, Mato Grosso; Brazil, Parana; HLIF; WSA; POC; NT; SOC; Aggregate-C pathway; MT; NV; LIFS; MGD; Biomass-C input; CT; LRV; HWEOC; TPS; ASI; PG; RI; Aggregate hierarchy; MWD; Labile fractions; Soil organic carbon; OM; Organic carbon; Subtropical zone; Tropical zone; Zero tillage; Biomass; Plowing; Soils; Decrease; Restoration; Instability; Soil science; Aggregate
• ISSN: 0167-1987; 1879-3444
• DOI: 10.1016/j.still.2012.09.004

► An aggregate hierarchy was evident at the sub-tropical and tropical sites. ► Continuous plow tillage negatively affected aggregation indices and aggregate-C concentrations. ► The 8–19mm aggregate size dominated the distribution under NV and NT. ► Diverse biomass-C inputs under NT restore macroaggregation and SOC stock. ► Difference between CT and NT is attributed to SOC storage in the 8–19mm fraction. Encapsulation of soil organic carbon (SOC) within aggregates is one of the principal mechanisms for long-term C sequestration, macroaggregate formation and stabilization. Our objectives were to quantify the changes in aggregate size distribution, aggregate-C concentrations and stocks upon conversion of native vegetation (NV) to conventional plow-based tillage (CT), and to assess the rate of aggregation and SOC recovery with no-till (NT) under diverse biomass-C inputs. The study was conducted at both sub-tropical (Ponta Grossa – PG, State of Paraná) and tropical (Lucas do Rio Verde – LRV, State of Mato Grosso) sites in Brazil. The SOC content under NV was used as a baseline to evaluate the depletion rate under CT and the restoration rate under NT. A specific emphasis was given to the largest macroaggregate size class (8–19mm) because of its importance to protecting the recently deposited labile SOC. A discriminant analysis of principal components (DAPC) indicated that NV soil is modified by conversion to an arable land use and that, mechanical tillage, biomass input, and their interactions drastically influence the distribution of aggregate-size classes, aggregation indices, and SOC distribution within aggregates. At both sites, soil aggregation indices were positively impacted by NT and associated with SOC concentration in the labile fractions (e.g., total polysaccharides (TPS), hot water extractable organic C (HWEOC), particulate organic C (POC)). At the PG site, the 8–19mm aggregate size fraction was significantly affected by land use and tillage treatments and represented 54%, 43%, and 72%, under NV, CT, and NT in 0–20cm depth, respectively. Furthermore, the 8–19mm size fraction stored 55%, 45%, and 71% of the total SOC stock under NV (53.8MgCha−1), CT (28.5MgCha−1) and NT (51.2MgCha−1), respectively. At the LRV site, the 8–19mm aggregate size fraction decreased from 50% under Cerrado NV to 35% under CT, and ranged from 33% to 51% under diverse biomass-C input under NT in 0–20cm depth. The 8–19mm size fraction stored 52%, 37%, and 41% of the total SOC stock across all aggregate sizes under NV (25.4MgCha−1), CT (11.7MgCha−1), and NT (9.9–18.1MgCha−1), respectively. The difference in SOC stock among land uses is largely attributed to storage in the 8–19mm aggregate size class, indicating that NT cropping systems rebuilt the largest macroaggregates, which are crucial for stabilization of SOC.