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Title: Similarities in chemical composition of soil organic matter across a millennia-old paddy soil chronosequence as revealed by advanced solid-state NMR spectroscopy

Author
item ZHOU, ZHIGAO - Old Dominion University
item CAO, XIAOYAN - Old Dominion University
item SCHMIDT-ROHR, KLAUS - Iowa State University
item Olk, Daniel - Dan
item ZHUANG, SHUNYAO - Chinese Academy Of Sciences
item ZHOU, JING - Chinese Academy Of Sciences
item CAO, ZHIHONG - Chinese Academy Of Sciences
item MAO, JINGDONG - Old Dominion University

Submitted to: Biology and Fertility of Soils
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2013
Publication Date: 5/1/2014
Publication URL: http://handle.nal.usda/gov/10113/58907
Citation: Zhou, Z., Cao, X., Schmidt-Rohr, K., Olk, D.C., Zhuang, S., Zhou, J., Cao, Z., Mao, J. 2014. Similarities in chemical composition of soil organic matter across a millenia-old paddy soil chronosequence as revealed by advanced solid-state NMR spectroscopy. Biology and Fertility of Soils. 50:571-581.

Interpretive Summary: Carbon contributes to several favorable soil processes, including nutrient availability, water infiltration, and biological activity. Crop production can affect the amount and composition of carbon in soil, which might change soil properties. Paddy rice has been produced for thousands of years in Asia, but very little is known about how the amount and composition of soil carbon have changed under such long-term rice cropping. We found that the composition of soil carbon changed very little from 50 years to 2000 years after a rotation of rice and wheat cropping was begun on soils in China. These results suggest that soil properties that are affected by carbon composition are unlikely to change noticeably after the first 50 years of rice and wheat rotation. This work is useful to researchers who study the effects of long-term crop production on soil carbon composition and to agronomists who are interested in maintaining the long-term sustainability of rice and wheat production.

Technical Abstract: Soil organic matter (SOM) accumulation in paddy soils has aroused considerable attention due to its vital significance in global food, energy, climate, and environmental issues. Considerable progress has been made toward the understanding of changes in the quantity of SOM in paddy soils over a millennial timescale, but changes in SOM quality over the same time are much less known. This study examined the changes in chemical composition of SOM along a 2000-year paddy soil chronosequence in eastern China by use of advanced solid-state nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy (FTIR), aiming to identify changes in the chemical nature of SOM over a millennium timescale. The results show that soil organic carbon (SOC) concentration in the surface soil on coastal tidal flats reached a steady stage after 100 years of rice (Oryza sativa L.)-wheat (Triticum sp.) cropping. The FTIR spectral pattern of whole SOM was similar along the soil chronosequence. Some differences in peak intensities were associated with carbon concentrations in SOM samples. The 13C nuclear magnetic resonance (NMR) spectra of the whole SOM samples also differed little along the chronosequence, suggesting a similar chemical composition in SOM samples, regardless of the rice cultivation duration. The similarities in chemical composition of SOM can be attributable to the rice-wheat cropping system, in which SOM has undergone ongoing turnover under periodical input of fresh plant material and wet-dry cropping alternation, leading to similar chemical composition in bulk SOM.