Key Laboratory of Land Resources Evaluation and Monitoring in Southwest China, Ministry of Education, Sichuan Normal University, Chengdu, Sichuan Province 610066, PR China; College of Natural Resources and Environment, Northwest A & F University, Yangling, Shaanxi Province 712100, PR China.
College of Natural Resources and Environment, Northwest A & F University, Yangling, Shaanxi Province 712100, PR China.
Sci Total Environ. 2020 Jun 10;720:137633. doi: 10.1016/j.scitotenv.2020.137633. Epub 2020 Feb 28.
In flooded paddy soils, some metal reducers are also capable of nitrogen (N) fixation, which is essential in ensuring a reliable N-supply for rice growth. Microbial iron [Fe(III)] reduction is an important biogeochemical process that can be stimulated by ferrihydrite amendment to paddy soil. Therefore, this study aimed to investigate the abundance and succession of the N-fixing bacterial community in ferrihydrite enriched paddy soils collected from Hunan (HN) and Sichuan (SC) provinces, China. The relationship between the N-fixing bacterial community and Fe(III) reduction was also assessed. When compared with the control treatment, ferrihydrite enrichment significantly enhanced nitrogenase (nifH) gene abundance by 8.05 × 10 to 4.45 × 10 copies g soil during the 40-day flooding of HN soil, while nifH gene abundance in SC soil was remarkably increased by 5.90 × 10 to 9.56 × 10 copies g soil during day 1 to 5 in response to ferrihydrite amendment. The relative abundance of N-fixing bacteria peaked on day 5 (21.5% in HN soil and 5.4% in SC soil) and gradually decreased to a stable abundance after day 20. Remarkable increases in relative abundance of N-fixing bacteria during the first 10 days of flooding were detected in both soils with ferrihydrite enrichment, whereas little difference was found after day 10 of flooding. During the early stage of flooding, the Shannon and Simpson indexes of N-fixing bacteria with ferrihydrite enrichment were significantly decreased, and the community structure changed greatly. Most N-fixing bacteria in ferrihydrite enriched paddy soils were phylogenetically related to the order Clostridiales, with some of those potentially capable of Fe(III) reduction. The community succession of N-fixing bacteria closely correlated with Fe(III) reduction. Thus, improving N-fixation via stimulation of Fe(III) reduction might aid in the reduction of N-fertilizer application to paddy field.
在水淹稻田中，一些金属还原剂也能够进行氮（N）固定，这对于确保水稻生长的可靠 N 供应至关重要。微生物铁[Fe(III)]还原是一种重要的生物地球化学过程，可以通过向稻田土壤添加水铁矿来刺激。因此，本研究旨在调查中国湖南（HN）和四川（SC）两省水铁矿富集稻田中固氮细菌群落的丰度和演替。还评估了固氮细菌群落与 Fe(III)还原之间的关系。与对照处理相比，水铁矿富集在 HN 土壤的 40 天淹水期间将固氮酶（nifH）基因丰度显著提高了 8.05×10 至 4.45×10 拷贝 g 土壤，而 SC 土壤中的 nifH 基因丰度在水铁矿添加后的第 1 至 5 天内显著增加了 5.90×10 至 9.56×10 拷贝 g 土壤。固氮细菌的相对丰度在第 5 天达到峰值（HN 土壤为 21.5%，SC 土壤为 5.4%），并在 20 天后逐渐稳定。在水铁矿富集的两种土壤中，淹水的前 10 天固氮细菌的相对丰度均显著增加，而淹水 10 天后则差异不大。在淹水的早期阶段，水铁矿富集的固氮细菌的 Shannon 和 Simpson 指数显著降低，群落结构发生了很大变化。水铁矿富集稻田中的大多数固氮细菌与梭菌目（Clostridiales）密切相关，其中一些可能具有 Fe(III)还原能力。固氮细菌群落的演替与 Fe(III)还原密切相关。因此，通过刺激 Fe(III)还原来提高固氮作用可能有助于减少稻田对氮肥的应用。
