Long-term field trials are ideal for characterising soil microbial communities because lasting communities in a given cropping system evolve over a long time. However, the soil microbiome has not been characterized in most long-term trials. We used a field trial established in 1911 to identify the core soil bacteria and their functioning in century-old wheat rotations, and how soil moisture deficit affected them. We collected soil samples from three wheat rotations: continuous wheat (W), fallow-wheat (FW) and fallow-wheat-wheat (FWW), all with or without N + P fertilizer, and incubated them with or without soil moisture deficit. The crop rotation effects on microbial biomass C (MBC) were in the order: W > FWW = FW. Fertilizer increased soil MBC by 21%. The activities of β-glucosidase (C cycling), N-acetyl-β-glucosaminidase (C and N cycling), and acid phosphomonoesterase (P cycling) followed similar trends, as did soil N supply measured in the field. The α-diversity of the soil bacteria was lower in continuous wheat than in the other rotations, and decreased with fertilizer application. Actinobacteria and Bacteroidetes were more abundant in continuous wheat than other rotations, and the relative abundance of Bacteroidetes increased with fertilizer application. By contrast, Acidobacteria were less abundant in continuous wheat than in other rotations. Soil moisture deficit during incubation had no effects on the soil microbiome. The core bacterial genera present in 90% of the soil samples were Bradyrhizobium, Rubrobacter, Friedmanniela and Marmoricola. β-diversity analysis revealed that the bacterial community structure in continuous wheat with fertilizer application was different from the structures in the other treatments. These and previously-published soil organic C, N and wheat yield results suggest that microbe-mediated nutrient cycling enabled sustainable continuous wheat cropping when fertilizer was applied.

长期田间试验是表征土壤微生物群落的理想选择，因为给定种植系统中的持久群落经过很长时间的演变。然而，大多数长期试验并未对土壤微生物组进行表征。我们使用 1911 年建立的田间试验来确定核心土壤细菌及其在百年小麦轮作中的功能，以及土壤水分亏缺如何影响它们。我们从三个小麦轮作中收集土壤样品：连续小麦 (W)、休耕小麦 (FW) 和休耕小麦 (FWW)，均使用或不使用 N + P 肥料，并在有或没有土壤水分亏缺的情况下进行培养。轮作对微生物生物量 C (MBC) 的影响顺序为：W > FWW = FW。肥料使土壤 MBC 增加了 21%。β的活动-葡萄糖苷酶（碳循环），N -乙酰- β-氨基葡萄糖苷酶（C 和 N 循环）和酸性磷酸单酯酶（P 循环）遵循类似的趋势，在田间测量的土壤 N 供应也是如此。连麦中土壤细菌的 α 多样性低于其他轮作，并且随着施肥的增加而降低。连续小麦中放线菌和拟杆菌比其他轮作更丰富，拟杆菌的相对丰度随着施肥的增加而增加。相比之下，酸杆菌连续小麦的含量低于其他轮作。孵化期间土壤水分亏缺对土壤微生物组没有影响。90% 的土壤样品中存在的核心细菌属是慢生根瘤菌属、红杆菌属、弗里德曼尼拉菌属和Marmoricola 属。β-多样性分析表明，连续施肥小麦的细菌群落结构与其他处理不同。这些以及之前发表的土壤有机碳、氮和小麦产量结果表明，当施肥时，微生物介导的养分循环使小麦可持续连续种植成为可能。