Carbon Sequestration in Clay Mineral Fractions from 14C‐Labeled Plant Residues

An understanding of organic C dynamics in soils is necessary to develop management options to enhance soil organic C sequestration. The objective of this research was to study the distribution of newly formed humic materials into mineralogically distinct clay-size fractions of a silt loam soil. Oats (Avena sativa L. cv. Ogle), grown under simulated no-tillage conditions, were pulse labeled with 14 CO 2 . After senescence, the labeled surface residue was removed and replaced with unlabeled residue and the labeled roots were allowed to decompose in the soil for 360 d. The soil clay fraction (<2 μm) was separated into coarse, medium, and fine clay size-fractions (0.2-2.0, 0.02-0.2, and <0.02 μm, respectively) by centrifugation. X-ray diffraction indicated that quartz, illite, and kaolinite were the dominant mineral phases in the coarse clay fraction while smectite was the dominant mineral phase in the fine clay fraction. The organic C content in the coarse and fine clay fractions (3.70 and 3.93%, respectively) was similar. Scintillation analysis indicated an increase in 14 C specific activity in all fractions after 360 d of incubation. For both sampling times, 0 and 360 d, the highest 14 C specific activity occurred in the fine clay fraction (847.2 and 1529 Bq g -1 C, respectively), whereas the lowest 14 C specific activity occurred in the coarse clay fraction (565.8 and 770.9 Bq g -1 C, respectively). The results suggest that new humic materials are preferentially forming or accumulating on smectite surfaces.

[1]  L. Mayer,et al.  Mesodensity organo–clay associations in a near-shore sediment , 2000 .

[2]  M. Kleber,et al.  Carbon storage in loess derived surface soils from Central Germany: Influence of mineral phase variables , 2002 .

[3]  Y. Furukawa.  Energy-filtering transmission electron microscopy (EFTEM) and electron energy-loss spectroscopy (EELS) investigation of clay–organic matter aggregates in aquatic sediments , 2000 .

[4]  D. Laird,et al.  Sorption of atrazine on Soil Clay Components. , 1994, Environmental science & technology.

[5]  L. H. Sørensen,et al.  The distribution of native and labelled carbon between soil particle size fractions isolated from long‐term incubation experiments , 1985 .

[6]  D. Laird.  Nature of Clay–Humic Complexes in an Agricultural Soil , 2001 .

[7]  D. Laird,et al.  Suspension Nebulization Analysis of Clays by Inductively Coupled Plasma-Atomic Emission Spectroscopy , 1991 .

[8]  D. Laird,et al.  Nature of the Illitic Phase Associated with Randomly Interstratified Smectite/Illite in Soils , 1993 .

[9]  S. Saggar,et al.  Particle Size Fractions and Their Use in Studies of Soil Organic Matter: I. The Nature and Distribution of Forms of Carbon, Nitrogen, and Sulfur1 , 1981 .

[10]  J. Baldock,et al.  Role of the soil matrix and minerals in protecting natural organic materials against biological attack , 2000 .

[11]  L. H. Sørensen,et al.  Carbon-nitrogen relationships during the humification of cellulose in soils containing different amounts of clay , 1981 .

[12]  S. Saggar,et al.  14C-labelled glucose turnover in New Zealand soils , 1999 .

[13]  Paul van Genuchten,et al.  Amount and composition of clay-associated soil organic matter in a range of kaolinitic and smectitic soils , 2001 .

[14]  G. Catroux,et al.  Chemical, spectroscopic, and biological characteristics of the organic matter in particle size fractions separated from an Aquoll , 1987 .

[15]  L. Lavkulich,et al.  ORGANIC MATTER DISTRIBUTION WITH PARTICLE-SIZE IN SURFACE HORIZONS OF SOME SOMBRIC SOILS IN VANCOUVER ISLAND , 1980 .

[16]  B. Christensen.  Decomposability of organic matter in particle size fractions from field soils with straw incorporation , 1987 .

[17]  J. Oades,et al.  Fractionation of organo-mineral complexes by sedimentation and density techniques , 1979 .

[18]  M. Kastner,et al.  ORGANIC MATTER PRESERVATION ON CONTINENTAL SLOPES: IMPORTANCE OF MINERALOGY AND SURFACE AREA , 1998 .

[19]  C. Cambardella,et al.  Carbon Dynamics of Surface Residue– and Root‐derived Organic Matter under Simulated No‐till , 2000 .

[20]  N. Scott,et al.  Factors Controlling Soil Carbon Levels in New Zealand Grasslands Is Clay Content Important , 2000 .

[21]  D. Anderson,et al.  Organo-Mineral Complexes and Their Study by Radiocarbon Dating1 , 1984 .

[22]  B. Christensen.  Straw incorporation and soil organic matter in macro-aggregates and particle size separates , 1986 .

[23]  A. Parshotam,et al.  14C-labelled ryegrass turnover and residence times in soils varying in clay content and mineralogy , 1996 .

[24]  D. Laird,et al.  Chemistry of smectitic and illitic phases in interstratified soil smectite , 1991 .