Shi Yichao, Gahagan Alison Claire, Morrison Malcolm J, Gregorich Edward, Lapen David R, Chen Wen
Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, 960 Carling Ave., Ottawa, ON K1A 0C6, Canada.
Department of Biology, University of Ottawa, 60 Marie Curie Prv., Ottawa, ON K1N 6N5, Canada.
Microorganisms. 2024 Aug 10;12(8):1635. doi: 10.3390/microorganisms12081635.
Understanding the soil bacterial communities involved in carbon (C) and nitrogen (N) cycling can inform beneficial tillage and crop rotation practices for sustainability and crop production. This study evaluated soil bacterial diversity, compositional structure, and functions associated with C-N cycling at two soil depths (0-15 cm and 15-30 cm) under long-term tillage (conventional tillage [CT] and no-till [NT]) and crop rotation (monocultures of corn, soybean, and wheat and corn-soybean-wheat rotation) systems. The soil microbial communities were characterized by metabarcoding the 16S rRNA gene V4-V5 regions using Illumina MiSeq. The results showed that long-term NT reduced the soil bacterial diversity at 15-30 cm compared to CT, while no significant differences were found at 0-15 cm. The bacterial communities differed significantly at the two soil depths under NT but not under CT. Notably, over 70% of the tillage-responding KEGG orthologs (KOs) associated with C fixation (primarily in the reductive citric acid cycle) were more abundant under NT than under CT at both depths. The tillage practices significantly affected bacteria involved in biological nitrogen (N) fixation at the 0-15 cm soil depth, as well as bacteria involved in denitrification at both soil depths. The crop type and rotation regimes had limited effects on bacterial diversity and structure but significantly affected specific C-N-cycling genes. For instance, three KOs associated with the Calvin-Benson cycle for C fixation and four KOs related to various N-cycling processes were more abundant in the soil of wheat than in that of corn or soybean. These findings indicate that the long-term tillage practices had a greater influence than crop rotation on the soil bacterial communities, particularly in the C- and N-cycling processes. Integrated management practices that consider the combined effects of tillage, crop rotation, and crop types on soil bacterial functional groups are essential for sustainable agriculture.
了解参与碳（C）和氮（N）循环的土壤细菌群落，可为可持续性和作物生产的有益耕作及作物轮作实践提供参考。本研究评估了长期耕作（传统耕作[CT]和免耕[NT]）及作物轮作（玉米、大豆和小麦单作以及玉米-大豆-小麦轮作）系统下，两个土壤深度（0-15厘米和15-30厘米）处与碳氮循环相关的土壤细菌多样性、组成结构和功能。利用Illumina MiSeq对16S rRNA基因V4-V5区域进行元条形码分析，对土壤微生物群落进行了表征。结果表明，与CT相比，长期NT降低了15-30厘米深度处的土壤细菌多样性，而在0-15厘米深度处未发现显著差异。NT条件下，两个土壤深度的细菌群落差异显著，而CT条件下则不显著。值得注意的是，在两个深度处，与碳固定（主要在还原性柠檬酸循环中）相关的超过70%的对耕作有响应的京都基因和基因组百科全书直系同源基因（KEGs）在NT条件下比在CT条件下更为丰富。耕作方式显著影响了0-15厘米土壤深度处参与生物固氮的细菌，以及两个土壤深度处参与反硝化作用的细菌。作物类型和轮作制度对细菌多样性和结构的影响有限，但显著影响了特定的碳氮循环基因。例如，与卡尔文-本森循环中碳固定相关的三个KEGs以及与各种氮循环过程相关的四个KEGs在小麦土壤中比在玉米或大豆土壤中更为丰富。这些发现表明，长期耕作方式对土壤细菌群落的影响大于作物轮作，特别是在碳氮循环过程中。考虑耕作、作物轮作和作物类型对土壤细菌功能群综合影响的综合管理实践对可持续农业至关重要。
