Soil organic carbon distribution drives microbial activity and functional diversity in particle and aggregate-size fractions

Protection of soil organic carbon and acid-hydrolyzable carbohydrates in aggregate-size fractions is important for appraising soil degradation and aggregation under land use types. Aggregate-associated soil organic carbon (SOC) and acid-hydrolyzable carbohydrates (R-CHO) in bulk soils and aggregate-size fractions of a sandy loam soil under Alchornea bush, Rubber, Oil palm and Teak plantations in southern Nigeria were studied. Results revealed significant differences in aggregate-associated SOC and R-CHO, bulk densities, total porosity, soil organic carbon stock and aggregate stability among the land use types. Greater SOC was stored in macro-aggregates >0.25 mm, while greater R-CHO was occluded in micro-aggregates <0.25 mm (p<0.05). The highest mean weight diameter (MWD) was 1.01 mm in Alchornea soils and 0.92 mm in Oil palm plantation at 0-15 cm topsoil. Soil organic carbon stock in 0-15 cm topsoil was 77.7, 81.8, 92.2, and 67.5 kg C ha-1 in Alchornea, Rubber, Oil palm, and Teak soils, respectively. Relationships showed a positive linear correlations between MWD and SOC (r = 0.793, p < 0.05) and R-CHO (r = 0.789. p < 0.05). Alchornea bush and Oil palm plantation increased macro-aggregate formation and macro-pores >5 µm, therefore they have greater potentials to boost protection of SOC in soil macro-aggregates.

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Distribution of soil organic carbon within aggregate size fractions following the conversion of cropland to black locust forest on the southern Loess Plateau, China

Journal of Soil and Water Conservation ◽

10.2489/jswc.74.1.59 ◽

2018 ◽

Vol 74 (1) ◽

pp. 59-66 ◽

Cited By ~ 1

Author(s):

B.Q. Li ◽

G.L. Li ◽

Y. Fu ◽

K. Wang

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Loess Plateau ◽

Black Locust ◽

Aggregate Size ◽

Size Fractions

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Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. III. Distribution and kinetics of soil organic carbon in particle size fractions

Soil Research ◽

10.1071/sr9860293 ◽

1986 ◽

Vol 24 (2) ◽

pp. 293 ◽

Cited By ~ 67

Author(s):

RC Dalal ◽

RJ Mayer

Keyword(s):

Particle Size ◽

Organic Matter ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Size Fraction ◽

Organic C ◽

Size Fractions ◽

Particle Size Fractions ◽

Clay Size Fraction ◽

Sand Size

Distribution of soil organic carbon in sand-, silt- and clay-size fractions during cultivation for periods ranging from 20 to 70 years was studied in six major soils used for cereal cropping in southern Queensland. Particle-size fractions were obtained by dispersion in water using cation exchange resin, sieving and sedimentation. In the soils' virgin state no single particle-size fraction was found to be consistently enriched as compared to the whole soil in organic C in all six soils, although the largest proportion (48%) of organic C was in the clay-size fraction; silt and sand-size fractions contained remaining organic C in equal amounts. Upon cultivation, the amounts of organic C declined from all particle-size fractions in most soils, although the loss rates differed considerably among different fractions and from the whole soil. The proportion of the sand-size fraction declined rapidly (from 26% to 12% overall), whereas that of the clay-size fraction increased from 48% to 61% overall. The proportion of silt-size organic C was least affected by cultivation in most soils. It was inferred, therefore, that the sand-size organic matter is rapidly lost from soil, through mineralization as well as disintegration into silt-size and clay-size fractions, and that the clay fraction provides protection for the soil organic matter against microbial and enzymic degradation.

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