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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Soil, Water & Air Resources Research » Research » Publications at this Location » Publication #343312
Research Project: Managing Carbon and Nutrients in Midwestern U.S. Agroecosystems for Enhanced Soil Health and Environmental Quality

Location: Soil, Water & Air Resources Research

Title: Distinct changes in composition of soil organic matter with length of cropping time in subsoils of a Phaeozem and Chernozem

Author
item ZHANG, YUELING - Chinese Academy Of Agricultural Sciences
item LI, LUJUN - Chinese Academy Of Sciences
item MAO, JINGDONG - Old Dominion University
item YAO, SHUI-HONG - Chinese Academy Of Agricultural Sciences
item SCHMIDT-ROHR, KLAUS - Brandeis University
item Olk, Daniel - Dan
item CAO, XIAO-YAN - Brandeis University
item CUI, JIN-FANG - Iowa State University
item ZHANG, BIN - Chinese Academy Of Agricultural Sciences

Submitted to: European Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2018
Publication Date: 7/12/2018
Publication URL: http://handle.nal.usda.gov/10113/6117413
Citation: Zhang, Y., Li, L., Mao, J., Yao, S., Schmidt-Rohr, K., Olk, D.C., Cao, X., Cui, J., Zhang, B. 2018. Distinct changes in composition of soil organic matter with length of cropping time in subsoils of a Phaeozem and Chernozem. European Journal of Soil Science. https://onlinelibrary.wiley.com/doi/pdf/10.1111/ejss.12688.
DOI: https://doi.org/10.1111/ejss.12688

Interpretive Summary: Natural organic matter plays important roles in soil performance and water quality. Its performance can be affected by its composition, but knowledge is incomplete regarding how its composition changes by soil depth and whether these changes are consistent for different types of soil. We identified the components of natural organic matter at several depths in two types of soils and at locations that differed in the years of crop production that had been practiced since these soils were converted from grasslands. We found that the components of natural organic matter changed by depth, but in different manners for the soil types. The duration of agriculture affected the composition of natural organic matter in deeper depths but not near the soil surface. These results indicate that the composition of natural organic matter depends on multiple factors, which complicates the prediction of natural organic matter behavior. These results are of interest to researchers who study soil processes or components of natural organic matter.

Technical Abstract: Soil organic matter (SOM) contributes to soil processes and is found both in shallow and deep soil layers. Its activity can be affected by its chemical composition, yet knowledge is incomplete of how land use alters the structural composition of SOM throughout the profiles of different soil types. The objective of this study was to determine the effects of cropping time after conversion of grassland on the chemical structures of SOM and its structural composition in Phaeozems and Chernozems in Northeast China by using quantitative multiple cross polarization (multiCP) 13C nuclear magnetic resonance (NMR) spectroscopy and principal component analysis. Eleven carbon functional groups were identified and the structural compositions were statistically separated by soil types and soil layers. The separations by soil types were driven in the Phaeozem profiles more by fused-ring aromatic C-C groups from plant-derived chars and in the Chernozem profiles more by crystalized (CH2)n groups from microbial- or plant-derived residues. The separations by soil layers were driven more by protonated C groups in the topsoils and by mobile and non-protonated C groups in the subsoils, indicating the varying effects of organic amendments by soil depth. The structural composition of SOM from the topsoils did not significantly change with cropping time, indicating no clear effect of crop straw additions. However, the structural composition of SOM from the subsoils changed over time, indicating the accumulation of more oxidized aromatics and loss of (CH2)n in the Phaeozems and accumulation of more crystalized (CH2)n in the Chernozems. Our findings demonstrated that the conversion of grassland into cropland in Northeast China altered the structural composition of SOM more in the subsoils than in the topsoils. The manner of alteration was associated with recalcitrant structures in the subsoils that differed by soil type, which might have been caused by precipitation-controlled soil processes.