长期秸秆还田对稻麦轮作区土壤有机碳组分构成的影响

为研究长期秸秆还田对太湖地区稻麦轮作土壤有机碳（soil organic carbon， SOC）含量的影响，依托10 a田间定位试验，以无秸秆还田为对照（CK），设置稻秸秆不还田+麦秸秆全量还田（W）、稻秸秆全量还田+麦秸秆不还田（R）、稻麦秸秆均半量还田（HRW）、稻麦秸秆均全量还田（ARW）4个秸秆还田处理，分析5种处理下SOC含量及其组分构成。结果表明，秸秆类型和还田量对SOC含量及其组分有显著影响。与2007年相比，2017年各处理SOC、重组分有机碳（heavy fraction organic carbon，HFOC）和轻组分有机碳（light fraction organic carbon，LFOC）含量的增速分别为0.18~0.46、0.15~0.42和-0.03~0.02 g·kg^-1·a^-1；R、HRW和ARW处理下SOC和HFOC含量显著增加；所有处理轻组分有机质中的碳含量均显著下降，其中，ARW处理的降幅最大；HFOC占比均大于80%，是SOC的主要组分，其中，W和HRW处理HFOC占比增加，其他处理HFOC占比下降；秸秆还田降低了SOC及其组分含量与水稻产量的相关性，LFOC对水稻产量影响更大。综上所述，稻麦秸秆均全量还田可增加SOC含量及稳定性，是太湖地区较为理想的秸秆还田模式。

Effect of Long-term Straw Returning on Soil Organic Carbon Fractions Composition in Rice-Wheat Rotation Ecosystem

In order to study the effect of long-term straw returning on content of soil organic carbon （SOC） in Taihu Lake rice-wheat rotation region， based on 10 years field positioning experiments， 4 treatments were set including no rice straw+all wheat straw returning （W）， all rice straw+no wheat straw returning （R）， half of rice straw and wheat straw returning （HRW） and all rice straw and wheat straw returning （ARW）， and no straw returning was control （CK）. The contents and components of SOC in different treatments were determined. The results showed that straw types and returning amounts significantly influenced the contents and compositions of SOC in rice-wheat rotation system. Compared with 2007， the growth rates of SOC， heavy fraction organic carbon （HFOC） and light fraction organic carbon （LFOC） were 0.18~0.46， 0.15~0.42 and -0.03~0.02 g·kg^-1·a^-1， respectively； the content of SOC and HFOC significantly increased in R， HRW and ARW treatments， and the carbon contents in light fraction organic matter （LFOM-C） decreased significantly in all treatments， which the decreased range of ARW treatment was more than other treatments. HFOC was the main component and accounted for more than 80% of SOC in all treatments， which the proportions of HFOC increased in W and HRW and decreased in CK， R and ARW treatments. Straw returning reduced the relationship between rice yield and the contents of SOC or components， and LFOC had more influence on rice yield than HFOC. In conclusion， all amount of rice and wheat straw returning could increase the content and stability of SOC， which could be considered as an ideal straw returning model in Taihu Lake region.