Many models have been constructed in an attempt to describe the dynamics of soil organic‐matter (SOM) turnover, most of which include 2 to 3 kinetically defined organic‐matter pools. Physical and chemical definition of these conceptualized SOM pools has been difficult. We describe a simple method for dispersion of soil to isolate a particulate organic‐matter (POM) fraction that may represent an important SOM pool in grassland soils. The POM fraction was isolated by dispersing the soil in 5 g L−1hexametaphosphate and passing the dispersed soil samples through a 53‐µm sieve. We compared POM and mineral‐associated C among three tillage treatments (20 yr under cultivation) and an undisturbed grassland at Sidney, NE. The POM C in the native sod represented 39% of the total soil organic C. Twenty years of bare‐fallow, stubble‐mulch, and no‐till management reduced the C content in this fraction to 18, 19, and 25%, respectively, of the total organic C. The mineral‐associated organic‐matter fraction showed no reduction in C content in the bare‐fallow treatment compared with the grassland soil but increased in the no‐till and stubble‐mulch treatments. Nitrogen dynamics generally mirrored those observed for C. Analysis of the POM fraction for lignin and cellulose content indicated that this fraction was 47% lignin and had a lignocellulose index of 0.7. The stable C‐isotope composition of the POM fraction suggests that wheat‐derived POM turns over faster than grass‐derived POM. We suggest the POM fraction closely matches the characteristics of a SOM pool variously described as slow, decomposable, or stabilized organic matter.

C. A. Cambardella

E. T. Elliott

Soil Science Society of America Journal

SSSA JOURNAL 发表土壤物理学内容；水文学；土壤化学；土壤生物学；土壤生物化学；土壤肥力；植物营养；土壤学；水土保持与管理；森林、山脉和荒地土壤；土壤和植物分析；土壤矿物学，湿地土壤。观众是研究人员、学生、土壤科学家、水文学家、土壤学家、地质学家、农学家、树木学家、生态学家、工程师、认证从业者、土壤微生物学家和环保主义者。该杂志发表原创研究、问题论文、评论、注释、评论和致编辑的信以及书评。如果被编委接受，邀请论文可以在期刊上发表。

The Soil Science Society of America Journal publishes research related to soil science, including soil physics, hydrology, soil chemistry, soil biology, soil biochemistry, soil fertility, plant nutrition, soil science, soil conservation and management, soils of forests, mountains, and wastelands, soil and plant analysis, soil mineralogy, and wetland soils. The journal's audience includes researchers, students, soil scientists, hydrologists, soil scientists, geologists, agronomists, foresters, ecologists, engineers, certified practitioners, soil microbiologists, and environmentalists. The journal accepts original research, issue papers, reviews, comments, letters to the editor, and book reviews. Invited papers may also be published in the journal if accepted by the editorial board.

《Soil Science Society of America Journal》发表与土壤科学相关的研究，包括土壤物理学、水文学、土壤化学、土壤生物学、土壤生物化学、土壤肥力、植物营养、土壤学、水土保持与管理、森林、山脉和荒地土壤、土壤和植物分析、土壤矿物学以及湿地土壤等领域。该期刊的读者群体包括研究人员、学生、土壤科学家、水文学家、土壤学家、地质学家、农学家、树木学家、生态学家、工程师、认证从业者、土壤微生物学家和环保主义者。期刊接受原创研究、问题论文、评论、注释、致编辑的信件以及书评。如果被编委接受，邀请论文也可以在期刊上发表。

Category	Quartile
农林科学	3
农林科学, 土壤科学	4

Particulate Soil Organic‐Matter Changes across a Grassland Cultivation Sequence

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Journal Info

Category	Quartile
SOIL SCIENCE	2