Soil Carbon Sequestration in Sorghum Cropping Systems: Evidence From Stable Isotopes and Aggregate-Size Fractionation
Soil Science(2014)
摘要
Management practices can influence both the quantity of soil organic carbon (SOC) and its distribution into different fractions or pools. We investigated SOC sequestration potentials of cropping systems in near-surface (0-5 cm) samples through soil size and density fractionation coupled with acid hydrolysis and natural abundance of stable isotopes (delta C-13) in a 20-year field study in the southern Great Plains in 2002. Treatments included two tillage regimens, conventional and no tillage (NT), in combination with two cropping systems: continuous grain sorghum [Sorghum bicolor (L.) Moench.] (CS) and a sorghum-wheat (Triticum aestivum L.)-soybean [Glycine max (L.) Merr.] (SWSoy) rotation, and with or without N fertilization. Tillage and cropping sequence significantly affected SOC distribution and the natural abundance of delta C-13 in different fractions. Samples from CS exhibited delta C-13 values ranging from -15% to -20%, suggesting most SOC was derived from this C-4 crop species. The delta C-13 values for soils from SWSoy varied from -20% to -22%, reflecting amixed input from C-3-derived and C-4-derived residue input. For whole soil and all aggregate-size fractions, SOC concentrations were significantly higher for NT than conventional tillage. However, the effects of cropping system and N fertilization on SOC interacted with tillage. Greater SOC for enhanced cropping (SWSoy) or N fertilization was observed only under NT. The fraction of <53 mu m represented a greater proportion of soil than other aggregate-size fractions. Our long-term study indicated that SOC and its various fractions, including more resistant, can be increased by NT with enhanced cropping and N fertilization.
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关键词
Tillage,cropping,carbon,natural abundance,stable isotopes,aggregate-size fractionation
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