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ARS Home » Plains Area » Lincoln, Nebraska » Agroecosystem Management Research » Research » Publications at this Location » Publication #300118
Title: Abundance of ammonia oxidizing bacteria and archaea under long-term maize cropping systems.

Author
item SEGAL, LAUREN - University Of Nebraska
item DRIJBER, RHAE - University Of Nebraska
item Miller, Daniel
item LOECKE, TERRY - University Of Nebraska

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/26/2013
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sustainable corn production depends upon the efficient use of nitrogen fertilizer. Ammonia-oxidizing (AO) microorganisms play an important role in determining the forms of nitrogen (either as nitrate or ammonium) in the soil. These microbes belong to one of two groups, archaea or bacteria, and understanding the environmental factors determining which group is dominant will be an important factor controlling nitrogen for efficient crop production. In this study, the effect of tillage and nitrogen fertilizer rates were investigated using long-term (25+ years) continuous corn plots. We found that AO archaea greatly outnumber AO bacteria, but the abundance of AO bacteria was much more responsive to tillage compared to the AO archaea. This research contributes to our understanding of efficient crop production and to the controls on carbon storage and greenhouse gas emissions from corn production systems.

Technical Abstract: Nitrification involves the oxidation of ammonium and is an important component of the overall N cycle. Nitrification occurs in two steps; first by oxidizing ammonium to nitrite, and then to nitrate. The first step is often the rate limiting step. Until recently ammonia-oxidizing bacteria were thought to be the sole contributors to this process; however, the discovery of crenarchaeota, ammonia-oxidizing archaea, in marine environments has led to further study of their role in nitrification. Current literature supports the dominance of archael over bacterial ammonia oxidizers in terrestrial ecosystems; however, little is known about what drives their abundance. To investigate the role of cropping system management on nitrifier abundance we sampled long-term continuous maize (25+ years) under two tillage treatments (tillage and no tillage) and five N fertilizer rates (0, 40, 80, 120, 160 kg ha-1 yr-1). Samples were collected four times during 2012; before fertilization, 2 weeks after fertilization and pre- and post- harvest. Quantitative PCR was used to determine the abundance of ammonia-oxidizing bacteria and archaea. In agreement with current literature, it was found that ammonia oxidizing archaea greatly outnumber bacteria. The low abundance of ammonia oxidizing bacteria in this long-term fertilized plot may be attributed to niche differentiation between archaea and bacteria, as it was found that bacterial abundance rather than archaeal abundance respond to fertilizer rates and tillage treatments in a monoculture system. This may have repercussions for N transformation important to plant N acquisition, carbon storage and greenhouse gas emissions.