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| Effects of straw returning on the stability of soil organic carbon in wheat-maize rotation systems |
| Received:January 03, 2020 |
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| KeyWord:straw returning;functional group;wheat-maize rotation;soil organic carbon stability |
| Author Name | Affiliation | E-mail | | WANG Xue-xia | Institute of Plant Nutrition and Resources, Beijing Agricultural Forestry Academy Sciences, Beijing 100097, China | | | ZHANG Lei | College of Resource and Environmental Sciences, Hebei Agricultural University, Baoding 071000, China | | | LIANG Li-na | Institute of Plant Nutrition and Resources, Beijing Agricultural Forestry Academy Sciences, Beijing 100097, China | | | SONG Ning-ning | School of Resources and Environment, Qingdao Agricultural University, Qingdao 266109, China | | | LIU Dong-sheng | Institute of Plant Nutrition and Resources, Beijing Agricultural Forestry Academy Sciences, Beijing 100097, China | | | WANG Jia-chen | Institute of Plant Nutrition and Resources, Beijing Agricultural Forestry Academy Sciences, Beijing 100097, China | 13021121195@163.com |
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| Abstract: |
| To explore the effects of different amounts of straw returning on the molecular composition and stability of soil organic carbon (SOC)in wheat-maize systems of North China, the functional group structure of SOC, proportions of aggregates and their organic carbon contents, active organic carbon contents, and iron ion contents were studied by a field experiment after 5 years of straw return. The field experiment included four treatments, namely no straw returning(CK), 1/3 straw returning(S1), 2/3 straw returning(S2), and total straw returning(S3), which were investigated in 2013. The soil physical and chemical properties, particle size, iron ion content, and microbial biomass carbon(MBC)content were determined by conventional methods, and the functional group structure of SOC was analyzed by 13C nuclear magnetic resonance. Our results indicated that the total organic carbon(TOC)content, organic carbon content of >2.00 mm and 2.00~0.25 mm aggregates, dissolved organic carbon content, easily oxidizable carbon content, and MBC content were increased gradually following the pattern of S3 > S2 > S1 > CK, and different increases were found in different treatments. Compared with those of CK, the organic carbon contents were significantly increased by S3(P<0.05). The functional groups of SOC in all the treatments were mainly alkyl carbon (alkyl-C)and alkoxy carbon(O-alkyl-C), followed by aromatic carbon(aromatic-C)and carbonyl carbon(carbonyl-C). O-alkyl-C and carbonyl-C(labile carbon component)showed an increasing trend with the increasing amount of straw returning; however, alkyl-C and aromatic-C(recalcitrant carbon component)showed different patterns. Compared with those of CK, the O-alkyl-C and alkyl-C contents were significantly increased(P<0.05) and significantly decreased(P<0.05) by S3, respectively. Compared with those of CK, the aromaticity, hydrophobic/hydrophilic C, and alkyl-C/O-alkyl-C were significantly decreased(P<0.05)by S2 and S3; however, the value of aliphatic/aromatic-C was not significantly affected by returning straw. Compared with those of CK, the components of >2.00 mm and 2.00~0.25 mm were significantly increased(P<0.05)and increased by S3, respectively. However, the components of 0.25~0.053 mm and <0.053 mm were decreased and significantly decreased(P<0.05)by S3, respectively. The contents of free iron, active iron, and chelated iron were not significantly influenced by straw returning. The relationship between the functional group structure of SOC and environmental factors determined by redundancy analysis showed that the changes in TOC, MBC content, aggregate composition, and iron ion content were important factors for revealing the differences in the SOC molecular structure among different treatments. In summary, the contents of active organic carbon, labile carbon, and the relatively simple molecular structure of SOC were increased, the recalcitrant carbon component and physical protection of microaggregates were decreased, and the microbial activity and iron ion complexation were changed by straw returning. This is not beneficial to the stability of SOC and may lead to the increase in the soil carbon emission level under wheat-maize cropping systems. |
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