耕作方式对旱地麦田土壤团聚体及其碳氮组分分布的影响

为明确蓄水保墒耕作方式下旱地麦田土壤团聚体稳定性、有机碳及碳组分和全氮及氮组分在不同粒径团聚体组分中的分布特征，深入了解不同耕作方式下土壤碳氮固持机制，以连续3 a(2017—2020年)实施不同耕作方式(免耕、深松、深翻)后冬小麦收获期0～20 cm土壤为研究对象，采用湿筛法测算土壤团聚体的构成与稳定性(R_0.25,>0.25 mm团聚体含量；MWD,平均重量直径；GMD,几何平均直径),并测定各粒径团聚体有机碳(SOC)和碳组分(重组有机碳，HFOC;轻组有机碳，LFOC;易氧化有机碳，EOC;可溶性有机碳，DOC;颗粒有机碳，POC)含量、全氮(TN)和氮组分(硝态氮，NO^-₃-N;铵态氮，NH⁺₄-N;可溶性有机氮，SON)含量，分析了碳氮组分的相关关系。结果显示：(1)免耕和深松处理>2 mm团聚体土壤比例较深翻处理分别提高8.8%和22.1%,免耕有利于增加<0.053 mm粉黏粒比例，较深松和深翻处理分别提高46.4%和27.7%。深松处理较深翻...

Effects of tillage methods on soil aggregation and aggregate\|associated carbon and nitrogen fractions in dryland wheat fields

The study aimed to investigate the soil aggregate stability, distribution characteristics of soil organic carbon (SOC) and its components, and total nitrogen (TN) and its fractions in water\|stable aggregates of dryland wheat field under different tillage methods and further understand the mechanism of soil carbon and nitrogen sequestration under different tillage methods. Topsoil samples (0~20 cm) for 3 consecutive years (2017-2020) were collected under three tillage methods (no tillage, subsoiling and deep tillage) after harvest in the third experimental season. A wet sieve method was used to analyze fractions of particle size, and distribution of carbon components (SOC, HFOC, LFOC, EOC, DOC, POC) and nitrogen components (TN, NO^-₃-N, NH⁺₄-N, SON). The relationship between carbon\|nitrogen components was examined. The results showed that, (1) >2 mm aggregates under no tillage and subsoiling treatments were 8.8% and 22.1% higher than that under deep tillage treatment. No tillage was conducive to increasing <0.053 mm silt and clay, and 46.4% higher than subsoiling and 27.7% higher than deep tillage. R_0.25, MWD and GMD under subsoiling treatment increased by 2.8%, 6.3% and 9.0% compared with deep tillage treatment. (2) The contents of SOC, LFOC, EOC, DOC and POC of soil aggregates in no tillage and subsoiling treatments were higher than those in deep tillage treatment. The content of HFOC in subsoiling treatment was higher than that in deep tillage, and the content of HFOC in no tillage was higher than that in deep tillage only in <0.053 mm. (3) The contents of TN, NO^-₃-N and NH⁺₄-N in >2 mm, 0.25~2 mm and 0.053~0.25 mm aggregates under no tillage treatment were higher than deep tillage, and the contents of <0.053 aggregates were lower than deep tillage. Compared with deep tillage treatment, subsoiling treatment increased TN contents of soil aggregates and NO^-₃-N contents of >2 mm and 0.25~2 mm aggregates, while NH⁺₄-N content was lower than that under deep tillage. The content of SON in no tillage and subsoiling was higher than that in deep tillage. The C/N ratio of aggregates under different particle sizes showed the fallow of subsoiling>no tillage>deep tillage. (4) The stocks of soil carbon under no\|tillage and subsoiling in 0~20 cm soil layer were 85.4% and 86.3% higher than that under deep tillage, soil nitrogen stocks were 48.1% and 32.5% higher than that under deep tillage, while the straw carbon return was higher under deep tillage. (5) Based on the structural equation model analysis, DOC and POC were the main factors affecting SOC change through synergistic EOC change. SON was the dominant factor affecting TN. In dryland wheat field of Loess Plateau, subsoiling improved soil aggregate structure, and increased soil organic carbon and total nitrogen contents.