摘要:自生固氮是陆地生态系统氮素的重要来源。本研究以位于西藏拉萨的肥料长期定位试验站为平台, 选取不施肥(CK)、单施化肥(F)、单施羊粪(M)、化肥配施羊粪(FM)和化肥配施秸秆(FS)5个处理, 于青稞收获期采集土样, 采用15N同位素标记、定量PCR和高通量测序技术, 分析不同施肥模式下土壤理化性质、固氮微生物丰度、群落结构和潜在固氮速率的变化规律, 以期为西藏高原青稞田制定科学合理的施肥策略, 保障西藏高原农业绿色发展提供科学依据。结果表明: 1)相比于CK和F处理, M、FM和FS处理可显著(P<0.05)提高土壤有机碳和全氮含量。FM处理下土壤铵态氮含量最高, 且显著高于其他施肥处理(P<0.05), 而M处理下土壤有机碳、全氮、硝态氮、有效磷和速效钾含量最高, 且显著高于其他施肥处理(P<0.05)。2)不同施肥处理下青稞田土壤潜在固氮速率为2.63~4.07 μg?kg?1?d?1。施肥会降低土壤潜在固氮速率, 增施有机肥(羊粪或秸秆)则加剧了抑制效应, 但羊粪的抑制效应小于秸秆, 土壤铵态氮含量是影响土壤潜在固氮速率的主要因子。3) M或FM处理可显著(P<0.05)提高nifH基因丰度, 而F或FS处理则相反, 土壤全氮含量是影响nifH基因丰度的关键因子。4)不同施肥模式显著改变了固氮微生物群落结构, 其群落结构相似性大致可以分为3类, 分别为CK、M以及施用化肥处理(F、FM和FS), 有效磷、pH和C/N是调控固氮微生物群落结构的关键因子。综上所述, 单施羊粪(M)处理是提高青稞田土壤肥力、增加固氮微生物丰度, 减少固氮速率下降幅度的最佳施肥模式。
关键词:施肥模式/
青稞农田/
自生固氮/
潜在固氮速率/
西藏高原
Abstract:Free-living nitrogen fixation (FLNF) by diazotrophs is an important nitrogen (N) source in terrestrial ecosystems and may reprensent a viable solution to environmental pollution caused by N over-fertilization. Studying the impact of different fertilizer regimes in highland barley fields on the diazotrophic community profiles and potential N fixation rates (PNFR) may provide scientific fertilization strategies and a theoretical basis for agricultural green development in the Tibetan Plateau. Here, quantitative PCR, high-throughput sequencing and 15N labeling methods were used to better understand the impact of different fertilizer regimes on the abundance and composition of diazotrophs as well as the potential N fixation rates in highland barley fields on the Tibetan Plateau. The experiment included five treatments: a control without fertilizer (CK); N, phosphorus (P) and potassium (K) mineral fertilzers (F); manure fertilizer (M); mineral NPK fertilizers plus manure (FM); and mineral NPK fertilizer plus straw (FS). The results showed that: 1) compared with the CK and F treatments, the M, FM and FS treatments significantly (P<0.05) increased the contents of soil organic carbon (C) and total N. Moreover, the ammonium nitrogen (NH4+-N) content was significantly (P<0.05) higher in the FM treatment than in the other treatments. The highest contents of organic C, total N, nitrate N (NO3?-N), available P and available K were observed in the M treatment, and their contents were significantly (P<0.05) higher than those in the other treatments. 2) The PNFR ranged from 2.63 to 4.07 μg?kg?1?d?1 under different fertilizer treatments. Fertilization, especially the application of organic fertilizers (sheep manure or straw), reduced the PNFR, and the inhibitory effect of straw on PNFR was higher than that of sheep manure. The soil NH4+-N content was the main factor affecting PNFR. 3) The M and FM treatments significantly (P<0.05) increased diazotrophic abundance, while the opposite was observed for the F and FS treatments. The total N content was the key factor affecting diazotrophic abundance. 4) Different fertilizer patterns significantly changed the diazotrophic composition, and the similarities in the diazotrophic compositions among different fertilizer regimes fell into three major categories: no fertilization (CK), organic fertilization (M), and chemical fertilization (F, FM, FS). Available P was the key factor regulating diazotrophic composition, followed by pH and C/N. In conclusion, the M treatment was the optimal fertilizer practice to improve soil fertility, increase diazotrophic abundance and reduce PNFR decline in highland barley fields on the Tibetan Plateau.
Key words:Fertilizer pattern/
Highland barley field/
Free-living N fixation/
Potential N fixation rate/
Tibetan Plateau
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