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Soil-specific inventories of landscape carbon and nitrogen stocks under no-till and native vegetation to estimate carbon offset in a subtropical ecosystem

De Moraes Sa J.C., Bürkner dos Santos J., Lal R., De Moraes A., Tivet F., Machado Sá M.F., Briedis C., De Oliveira Ferreira A., Eurich G., Farias A., Friedrich T.. 2013. Soil Science Society of America Journal, 77 (6) : p. 2094-2110.

DOI: 10.2136/sssaj2013.01.0007

Inventories of C and N footprints on a landscape scale are essential tools for estimating C offsets from agricultural emissions. Therefore, the aims of this study conducted in the subtropical humid ecosystem in southern Brazil were to: (i) conduct a soil-specific inventory of landscape soil C and N stocks with reference to soil order, soil texture, and land use/management type; (ii) estimate accretion rates for soil organic C (SOC) and total N (TN) for areas managed under no-till (NT) practices management with reference to native vegetation (NV) based on this inventory; (iii) generate a map of C stocks for each land use system; and (iv) calculate estimated C offset for the region through the use of NT compared to conventional tillage (CT). Soil samples were collected at 324 points to a 1-m depth from the entire region. Soil texture and duration of NT had a strong influence on C and N stocks. The average soil C stock across all types of soils for depths of 0-40 and 40-100 cm was 57.0 and 43.0%, respectively. The extrapolation of C stored in the 0- to 40-cm depth based on the NT management for 11 and 20 yr for 1.52 million hectare (Mha) was 9.08 ± 0.62 Tg (1 Tg = 1012 g) representing 11.9% of the C stored in all soil orders. The long-term of C sink capacity by conversion of arable land from CT to NT in this region is 33.2 Tg of CO2, with the C offset of 22.5% of all anthropogenic emissions.

Mots-clés : matière organique du sol; teneur en azote; propriété physicochimique du sol; mesure; cartographie; paysage; non-travail du sol; végétation; Écosystème; utilisation des terres; zone tropicale; stockage; carbone; séquestration du carbone; brésil

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