title: Effects of chlorimuron-ethyl application with or without urea fertilization on soil ammonia-oxidizing bacteria and archaea.
abstract: Chlorimuron-ethyl (CE) has been widely used in modern agriculture, but little is known regarding the influence of CE on ammonia-oxidizing bacteria (AOB) and archaea (AOA) populations in soils. In this study, microcosm incubation of aquic brown soil was conducted for 60 d. Associated changes in the population sizes of AOB and AOA in response to CE application with or without urea fertilization were examined via quantitative real-time PCR (qPCR) assays of the ammonia monooxygenase gene (amoA). The half-life of CE ranged from 11.80 d to 14.54 d in the tested soil. Compared to the untreated control, the application of CE alone had no strong effects on soil pH, and urea fertilization temporarily increased soil pH in the first 7 days. The abundance of the AOA amoA gene was greater than the abundance of the AOB amoA gene in all treatments, but both were significantly suppressed by CE application in a dose-dependent manner. Urea fertilization generally increased AOB and AOA amoA gene abundances, except that the AOA amoA gene level was slightly reduced at the early stage of the incubation period. AOB and AOA preferred different N levels for growth, with AOB only growing significantly at high NH4(+) levels and AOA growing substantially at low NH₄(+) levels. The stimulation effects of urea fertilization on AOA and AOB amoA gene abundances were strongly suppressed by the CE application. This study indicated that the CE application substantially suppressed soil nitrification via inhibiting the AOB and AOA population regardless of urea fertilization, which resulted in significant changes in the soil NH₄(+)-N and NO₃(-)-N levels. Furthermore, AOB and AOA inhabiting separate ecological niches with different NH₄(+) levels played various roles in N cycling.
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China.
authors.forename: Huanbo
authors.initials: H
authors.lastname: Tan
authors.forename: Mingkai
authors.initials: M
authors.lastname: Xu
authors.forename: Xinyu
authors.initials: X
authors.lastname: Li
authors.forename: Huiwen
authors.initials: H
authors.lastname: Zhang
authors.forename: Chenggang
authors.initials: C
authors.lastname: Zhang
mesh_terms: D000641:Ammonia / Q000737:chemistry; D001105:Archaea / Q000187:drug effects*; D001419:Bacteria / Q000187:drug effects*; D005308:Fertilizers; D006540:Herbicides; D006863:Hydrogen-Ion Concentration; D058465:Nitrification; D009584:Nitrogen / Q000737:chemistry; D010088:Oxidoreductases / Q000235:genetics; D011743:Pyrimidines / Q000737:chemistry*; D060888:Real-Time Polymerase Chain Reaction; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis*; D013453:Sulfonylurea Compounds / Q000737:chemistry*; D013696:Temperature; D014508:Urea / Q000737:chemistry*
chemical_list: D005308:Fertilizers; D006540:Herbicides; D011743:Pyrimidines; D012987:Soil; D012989:Soil Pollutants; D013453:Sulfonylurea Compounds; D000641:Ammonia; D014508:Urea; C112343:chlorimuron ethyl; D010088:Oxidoreductases; C045582:ammonia monooxygenase; D009584:Nitrogen
keywords: Ammonia-oxidizing archaea; Ammonia-oxidizing bacteria; Chlorimuron-ethyl; Real-time PCR