College of Resources and Environment, Academy of Agricultural Sciences, Southwest University, Chongqing 400716, China; Interdisciplinary Research Center for Agriculture Green Development in Yangtze River Basin, Southwest University, Chongqing 400716, China.
Center for Resources, Environment and Food Security, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
Sci Total Environ. 2022 Mar 10;811:151402. doi: 10.1016/j.scitotenv.2021.151402. Epub 2021 Nov 3.
Microbe-driven nitrification is a key process that affects nitrogen (N) utilization by plants and N loss to the environment in agro-ecosystems. Ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) are important microorganisms that dominate the ammonia oxidation process (the first and rate-limiting step of nitrification). Calcareous soils are widely distributed, accounting for more than 30% of the Earth's land. However, the effects of long-term N fertilization on the potential nitrification rate (PNR) and on AOA and AOB in calcareous soils are poorly understood. In this study, we comprehensively assessed the effects of N application (applied at five rates as urea with 0, 73.5, 105, 136.5 and 250 kg N ha for 12 years) on soil chemical characteristics, PNR, N use efficiency (NUE) and the community characteristics of AOB and AOA in a calcareous soil. N application rate affected AOB beta diversity more than that of AOA. Compared to no N control, N application significantly decreased the relative abundance of Group I.1b clade A of AOA and Nitrosospira cluster 3a.2 of AOB, but increased Nitrosomonas cluster 7 of AOB. The relative abundance of Nitrosospira cluster 3a.2 of AOB was negatively correlated with PNR. A structural equation model showed a direct effect of N application rate on the content of soil organic matter and nitrate, the alpha and beta diversity of AOA and AOB. Nitrate and AOB beta diversity were the key factors affecting PNR. Overall, the alpha, beta diversity and community composition of AOB contribute more to PNR than AOA in calcareous soils with high organic matter content. Understanding the relationship between the characteristics of AOA and AOB in calcareous soils and PNR will help to improve NUE.
微生物驱动的硝化作用是影响植物氮素利用和农业生态系统氮素向环境损失的关键过程。氨氧化细菌（AOB）和氨氧化古菌（AOA）是主导氨氧化过程（硝化作用的第一步和限速步骤）的重要微生物。石灰性土壤分布广泛，占地球陆地面积的 30%以上。然而，长期氮施肥对石灰性土壤中潜在硝化速率（PNR）以及 AOA 和 AOB 的影响还知之甚少。本研究全面评估了氮施用量（12 年期间以尿素的形式施用量为 0、73.5、105、136.5 和 250 kg N ha-1 的 5 个水平）对石灰性土壤化学特性、PNR、氮利用效率（NUE）和 AOB 和 AOA 群落特征的影响。氮施用量对 AOB 的 beta 多样性影响大于 AOA。与不施氮对照相比，氮施用量显著降低了 AOA 的 I.1b 群和 AOB 的 3a.2 群的相对丰度，但增加了 AOB 的 Nitrosomonas 群 7。AOB 的 3a.2 群的相对丰度与 PNR 呈负相关。结构方程模型表明，氮施用量直接影响土壤有机质和硝酸盐含量、AOA 和 AOB 的 alpha 和 beta 多样性。硝酸盐和 AOB 的 beta 多样性是影响 PNR 的关键因素。总的来说，在高有机质含量的石灰性土壤中，AOB 的 alpha、beta 多样性和群落组成对 PNR 的贡献大于 AOA。了解石灰性土壤中 AOA 和 AOB 的特征与 PNR 之间的关系将有助于提高 NUE。
