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| Changes of organic structures of crop residues during decomposition |
| Received:January 16, 2016 |
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| KeyWord:crop residue decomposition;infrared spectroscopy;structure |
| Author Name | Affiliation | E-mail | | CAO Ying-fei | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China
State Key Lab of Soil Erosion and Dryland Farming on Loess Plateau, Yangling 712100, China | | | ZHANG Hong | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China
State Key Lab of Soil Erosion and Dryland Farming on Loess Plateau, Yangling 712100, China | | | ZHAO Cong | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China | | | LIU Ke | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China | | | LÜ Jia-long | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China
State Key Lab of Soil Erosion and Dryland Farming on Loess Plateau, Yangling 712100, China | ljlll@nwsuaf.edu.cn |
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| Abstract: |
| In this study, field experiments were conducted in vineyard, peach orchard, and farmland to examine structural characteristics of organic substances in crop residues(corn stover and soybean stem) during decomposition, using nylon mesh bag method and fourier transform infrared(FTIR) spectroscopy. Results showed that corn and soybean residues had similar functional groups. However, FTIR absorption peaks and intensities were different at 3400, 1640, 1400~1460, 1310 and 1000~1100 cm-1 because of differences in content of amide compounds and silicon stable matters. The FTIR absorption peaks and intensities in crop residues changed after decomposition. With decomposition, hydroxyl, amide group, methyl, and methylene content in the residues reduced, but carboxyl increased, along with the formation of organic acids and the decomposition of carbohydrates, amide compounds and sugars. Those easily decomposable compounds such as aliphatic structure, amide compounds and sugars were directly decomposed, while aromatic substances with difficult decomposition first broke down to intermediates such as carboxylic acid esters(1725~1735 cm-1) and aliphatic structure(1450~1460 cm-1). The shoulder peak at 1560~1732 cm-1 was associated with organic acids in crop residues. Urea had a promoting effect on decomposition of corn residues, and influenced the absorption peak at 1310 cm-1. The residues mainly formed humic acid after decomposition. There were no obvious differences in organic structures among different land uses and between fresh and dry treatments(P >0.05). However, crop residue type and residue N content impacted structural changes. |
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