European Journal of Soil Science · 2009
Land use, tillage, texture and organic matter stock and composition in tropical and subtropical Brazilian soils
Dieckow, J., Bayer, C., Conceição, P. C., Zanatta, J. A., Martin Neto, L., Milori, D. B. M., Salton, J. C., Macedo, M. M., Mielniczuk, J., Hernani, L. C.
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Land use, tillage, texture and organic matter stock and comp…
Abstract
Summary We examined the influence of land use change, tillage system and soil texture on organic carbon (C) stocks and on organic matter composition of tropical and subtropical soils from Brazil at four long‐term experiments (11–25 years) based on fine‐ and coarse‐textured soils. Soil samples were collected from the 0–5, 5–10 and 10–20 cm layers of conventional tillage (CT) and no‐till (NT) plots, and of the adjoining soil under native vegetation (NV) of Cerrado (tropical) or grassland (subtropical). Conversion of NV to CT resulted in losses of 7–29% of the original C stock of 0–20 cm; conversion to NT increased this C stock by 0–12% compared with CT. Organic matter composition of the 0–5 cm layer, assessed by solid state CPMAS‐ 13 C‐NMR, ESR and laser induced fluorescence spectroscopies, was affected by land use and tillage systems. Conversion of NV to CT decreased O‐alkyl and increased aromatic, carbonyl, aromatic/O‐alkyl ratio, free radicals concentration and fluorescence signal. The opposite trend was observed when NT replaced CT. The relative losses and gains of C and qualitative changes resulting from land use and tillage were less evident in fine‐ than in coarse‐textured soils, suggesting a greater resistance and a smaller resilience of fine‐ compared with coarse‐textured soils. The direct relation between increase in C stock and increase in potentially labile moieties (e.g. O‐alkyl) and the decrease in more recalcitrant moieties (e.g. aromatics) in NT soils suggests that spatial inaccessibility by aggregates is playing a major role, compared with selective preservation, in promoting C accumulation in NT soils.
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Summary We examined the influence of land use change, tillage system and soil texture on organic carbon (C) stocks and on organic matter composition of tropical and subtropical soils from Brazil at four long‐term experiments (11–25 years) based on fine‐ and coarse‐textured soils. Soil samples were collected from the 0–5, 5–10 and 10–20 cm layers of conventional tillage (CT) and no‐till (NT) plots, and of the adjoining soil under native vegetation (NV) of Cerrado (tropical) or grassland (subtropical). Conversion of NV to CT resulted in losses of 7–29% of the original C stock of 0–20 cm; conversion to NT increased this C stock by 0–12% compared with CT. Organic matter composition of the 0–5 cm layer, assessed by solid state CPMAS‐ 13 C‐NMR, ESR and laser induced fluorescence spectroscopies, was affected by land use and tillage systems. Conversion of NV to CT decreased O‐alkyl and increased aromatic, carbonyl, aromatic/O‐alkyl ratio, free radicals concentration and fluorescence signal. The opposite trend was observed when NT replaced CT. The relative losses and gains of C and qualitative changes resulting from land use and tillage were less evident in fine‐ than in coarse‐textured soils, suggesting a greater resistance and a smaller resilience of fine‐ compared with coarse‐textured soils. The direct relation between increase in C stock and increase in potentially labile moieties (e.g. O‐alkyl) and the decrease in more recalcitrant moieties (e.g. aromatics) in NT soils suggests that spatial inaccessibility by aggregates is playing a major role, compared with selective preservation, in promoting C accumulation in NT soils.
Summary We examined the influence of land use change, tillage system and soil texture on organic carbon (C) stocks and on organic matter composition of tropical and subtropical soils from Brazil at four long‐term experiments (11–25 years) based on fine‐ and coarse‐textured soils. Soil samples were collected from the 0–5, 5–10 and 10–20 cm layers of conventional tillage (CT) and no‐till (NT) plots, and of the adjoining soil under native vegetation (NV) of Cerrado (tropical) or grassland (subtropical). Conversion of NV to CT resulted in losses of 7–29% of the original C stock of 0–20 cm; conversion to NT increased this C stock by 0–12% compared with CT. Organic matter composition of the 0–5 cm layer, assessed by solid state CPMAS‐ 13 C‐NMR, ESR and laser induced fluorescence spectroscopies, was affected by land use and tillage systems. Conversion of NV to CT decreased O‐alkyl and increased aromatic, carbonyl, aromatic/O‐alkyl ratio, free radicals concentration and fluorescence signal. The opposite trend was observed when NT replaced CT. The relative losses and gains of C and qualitative changes resulting from land use and tillage were less evident in fine‐ than in coarse‐textured soils, suggesting a greater resistance and a smaller resilience of fine‐ compared with coarse‐textured soils. The direct relation between increase in C stock and increase in potentially labile moieties (e.g. O‐alkyl) and the decrease in more recalcitrant moieties (e.g. aromatics) in NT soils suggests that spatial inaccessibility by aggregates is playing a major role, compared with selective preservation, in promoting C accumulation in NT soils.
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