Urea fertilization and grass species alter microbial nitrogen cycling capacity and activity in a C 4 native grassland

PeerJ

article

Jialin Hu¹  Jonathan D. Richwine²  Patrick D. Keyser²  Fei Yao¹  Sindhu Jagadamma¹  Jennifer M. DeBruyn¹ 

[1] Department of Biosystems Engineering and Soil Science, University of Tennessee;Department of Forestry, Wildlife, and Fisheries, University of Tennessee

关键词: Soil nitrogen cycling;    Diazotrophs;    Nitrifiers;    Denitrifiers;    Fertilization;    C4 grasslands;    Switchgrass (Panicum virgatum);    Big bluestem (Andropogon gerardii);    Ammonia oxidizing bacteria (AOB);   

DOI  :  10.7717/peerj.13874

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Soil microbial transformation of nitrogen (N) in nutrient-limited native C4 grasslands can be affected by N fertilization rate and C4 grass species. Here, we report in situ dynamics of the population size (gene copy abundances) and activity (transcript copy abundances) of five functional genes involved in soil N cycling (nifH, bacterial amoA, nirK, nirS, and nosZ) in a field experiment with two C4 grass species (switchgrass (Panicum virgatum) and big bluestem (Andropogon gerardii)) under three N fertilization rates (0, 67, and 202 kg N ha−1). Diazotroph (nifH) abundance and activity were not affected by N fertilization rate nor grass species. However, moderate and high N fertilization promoted population size and activity of ammonia oxidizing bacteria (AOB, quantified via amoA genes and transcripts) and nitrification potential. Moderate N fertilization increased abundances of nitrite-reducing bacterial genes (nirK and nirS) under switchgrass but decreased these genes under big bluestem. The activity of nitrous oxide reducing bacteria (nosZ transcripts) was also promoted by moderate N fertilization. In general, high N fertilization had a negative effect on N-cycling populations compared to moderate N addition. Compared to big bluestem, the soils planted with switchgrass had a greater population size of AOB and nitrite reducers. The significant interaction effects of sampling season, grass species, and N fertilization rate on N-cycling microbial community at genetic-level rather than transcriptional-level suggested the activity of N-cycling microbial communities may be driven by more complex environmental factors in native C4 grass systems, such as climatic and edaphic factors.

【 授权许可】

CC BY