摘要
为揭示不同秸秆还田量对华北小麦-玉米轮作系统土壤有机碳官能团结构及稳定性的影响,研究了秸秆还田5 a后土壤有机碳官能团结构、团聚体组成及有机碳含量、活性有机碳含量、土壤铁离子的变化。田间实验设置4个处理:秸秆不还田作为对照(CK)、秸秆1/3还田(S1)、秸秆2/3还田(S2)、秸秆全部还田(S3)。采用常规方法测定土壤理化性质、粒径、铁离子及土壤微生物量碳含量,13C核磁共振波谱技术(NMR)检测分析土壤有机碳官能团结构。结果表明:秸秆还田5 a后,土壤总有机碳(TOC)、>2mm与2.00~0.25 mm团聚体有机碳、可溶性有机碳(DOC)、易氧化态碳(EOC)和微生物量碳(MBC)含量,均随还田量增加而逐渐增加,且不同处理增加量不同,与CK相比,S3处理显著增加了这些有机碳的含量(P<0.05)。各处理土壤有机碳以烷基碳与烷氧基碳为主,其次是芳香碳与羰基碳,秸秆还田增加了烷氧基碳、羰基碳(易分解碳组分)含量,降低了烷基碳和芳香碳(难分解碳组分)含量,与CK相比,S3处理显著增加烷氧基碳含量(P<0.05)而显著降低了芳香碳含量(P<0.05)。与CK相比,S2、S3处理也显著降低了有机碳的芳香度、疏水碳/亲水碳、烷基碳/烷氧基碳比值(P<0.05),而对脂族碳/芳香碳影响不明显。与CK相比,S3处理显著增加了>2.00 mm团聚体组分,增加了2.00~0.25 mm组分,而降低了0.25~0.053 mm组分和显著降低了<0.053 mm组分(P<0.05)。秸秆还田对土壤游离铁、活性铁、螯合铁含量的影响不明显。有机碳官能团组成与土壤因子间的冗余分析表明土壤TOC、MBC含量、团聚体组分、铁离子的改变是导致不同处理间有机碳官能团结构存在差异的重要原因。综上所述,由于短期秸秆还田增加了活性有机碳含量、易分解有机碳组分,减少了难分解有机碳组分,降低了微团聚体物理保护作用,改变了微生物活性和铁离子络合作用,在一定程度上降低了土壤有机碳稳定性,可能导致麦玉复种系统土壤碳排放水平的增加。
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 by13 C nuclear magnetic resonance. Our results indicated that the total organic carbon(TOC)content, organic carbon content of >2.00 mm and2.00~0.25 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 and2.00~0.25 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.
作者
王学霞
张磊
梁丽娜
宋宁宁
刘东生
王甲辰
WANG Xue-xia;ZHANG Lei;LIANG Li-na;SONG Ning-ning;LIU Dong-sheng;WANG Jia-chen(Institute of Plant Nutrition and Resources,Beijing Agricultural Forestry Academy Sciences,Beijing 100097,China;College of Resource and Environmental Sciences,Hebei Agricultural University,Baoding 071000,China;School of Resources and Environment,Qingdao Agricultural University,Qingdao 266109,China)
出处
《农业环境科学学报》
CAS
CSCD
北大核心
2020年第8期1774-1782,共9页
Journal of Agro-Environment Science
基金
国家重点研发计划项目(2016YFD0200602,2018YFD0200603)
北京市农林科学院院创新计划项目(KJCX20200419)。
