连续秸秆还田和免耕对土壤团聚体及有机碳的影响

选取湖北省武穴市8年田间定位试验中的传统耕作(CT)、秸秆还田配合传统耕作(CTS)、免耕(NT)和秸秆还田配合免耕(NTS)4种处理,研究连续秸秆还田和免耕措施对表层(0—20cm)和亚表层(20—40cm)土壤团聚体稳定性及有机碳(SOC)的影响。结果表明:CTS、NT和NTS均显著增加了表层5mm水稳性团聚体的含量和团聚体平均重量直径(MWD),秸秆还田显著增加了亚表层土壤水稳性团聚体的MWD。与CT比较,CTS、NT、NTS处理的SOC含量分别增加20.83%,21.98%,32.76%。CTS和NTS处理显著提高了表层5,5~2,0.25mm团聚体中SOC含量,NT则显著提高了5,5~2mm团聚体中SOC含量;CTS显著增加了亚表层0.25 mm团聚体中SOC的含量。秸秆还田增加了表层土壤的碳(C)、氢(H)、氮(N)和氧(O)的含量,免耕降低了H的含量,增加了其他3种元素的含量,但是免耕处理增加了亚表层土壤中H的含量。NT和NTS处理较CT和CTS处理降低了土壤的H/C值,表明土壤的脂肪族成分在不断增加。秸秆还田主要增加了土壤中醇、酚类,芳香类,脂肪族化合物和碳水化合物的含量,而免耕主要增加脂肪族化合物的含量。这些有机组分的增加有助于团聚体稳定性的增强。

Effects of Continuous Straw Returning and No-tillage on Soil Aggregates and Organic Carbon

The effects of continuous straw returning and no-tillage on soil aggregate stability and contents of soil organic carbon (SOC) in topsoil (0 - 20 cm) and sub-surface soil (20 - 40 cm) were studied in paddy fields of subtropical China. Soil samples were collected from 8-year experimental field located in Wuxue city, Hubei province. Four treatments including conventional tillage (CT), straw returning with conventional tillage (CTS), no-tillage (NT) and straw returning with no-tillage (NTS), were designed. The results showed that CTS, NT and NTS treatments significantly increased the contents of water-stable aggregates greater than 5 mm and the mean weight diameters (MWD) of water-stable aggregates in the 0 - 20 cm soil layer, and straw returning significantly increased MWD of water-stable aggregates in the 20 - 40 cm layer. Compared with CT, the treatments of CTS, NT and NTS significantly increased the contents of SOC by 20.83%, 21.98% and 32.76%, respectively. In addition, CTS and NTS significantly increased the SOC contents in aggregates those > 5, 5 ~ 2 and <0.25 mm in diameter, and NT treatment significantly increased the SOC contents in the aggregates with diameter of >5 and 5 ~ 2 mm in the 0 - 20 cm soil layer. Meanwhile, the CTS treatment significantly increased the SOC contents of the aggregates greater than 0.25 mm in the 20 - 40 cm soil layers. Straw returning increased contents of carbon (C), hydrogen (H), nitrogen (N) and oxygen (O) in topsoil. In topsoil, no-tillage reduced the content of H, increased the contents of other three elements, but this treatment increased H content in sub-surface soil. Compared with the treatments of CT and CTS, the H/C ratios were reduced under NT and NTS treatments, indicating that the aliphatic components of soil were increasing. The contents of alcohol, phenol, aromatic, aliphatic compounds and carbohydrates in soil increased under straw returning treatment, while the no-tillage mainly increased the contents of aliphatic compounds. The increase of these organic components contributed to enhancement of aggregate stability.