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ARS Home » Midwest Area » Lexington, Kentucky » Forage-animal Production Research » Research » Publications at this Location » Publication #329894
Title: Tillage, not fertilization, dominantly influences the ammonia-oxidizing archaea in long-term maize

Author
item LIU, SHUANG - University Of Kentucky
item COYNE, MARK - University Of Kentucky
item GROVE, JOHN - University Of Kentucky
item Flythe, Michael

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: An abundance of nitrogen fertilizer is applied to agricultural lands all over the world. A major form of nitrogen, ammonium (NH4+), is converted to nitrate (NO3-) by nitrifying soil microorganisms (nitrifiers). Both nitrate and ammonium are available nutrients for plants, but nitrate can contaminate groundwater more easily. Nitric oxide (NO) and nitrous oxide (N2O) are also byproducts of nitrification and cause environmental problems. The nitrifiers can be either ammonia-oxidizing bacteria (AOB) or ammonia-oxidizing archaea (AOA). Archaea are a type of microorganisms that are not bacteria. AOA are more abundant than the very biologically active AOB in many soil systems, including croplands, and the AOA dominate in unfavorable environmental conditions, such as soils with low ammonium. However, the AOA are very difficult to grow in the laboratory, and their ecological roles are unclear. Consequently, we examined how long-term soil management such as tillage and fertilizer rate influenced AOA community structure in continuous maize plots. Unlike AOB, we discovered that tillage rather than nitrogen fertilizer most influenced the AOA community. Fertilizer rate did not significantly influence AOA diversity. Instead, tillage and the interaction of tillage and sampling season had significant influence on AOA diversity. In winter, AOA were more diverse in no-tillage than plow tillage plots. Unique groups were discovered in different treatments, demonstrating the selectivity of tillage, fertilization, season, and their interactions. The impact of the work is that significant tillage regulation of AOA provides a new clue to discover which environmental factors influence the AOA community and to explore its ecological significance in agricultural land management.

Technical Abstract: Ammonia-oxidizing archaea (AOA) catalyze the rate-limiting step in nitrification: ammonia (NH3) oxidation. AOA are more abundant than AOB in many soil systems, including cropland, and dominate in unfavorable environmental conditions, such as soils with low NH4-N. The ecological role of the ubiquitously distributed AOA is unclear and we do not know what factors regulate AOA community dynamics. This study investigated how long-term N fertilization and tillage management influenced the AOA community in cropland. The study site was a long-term (>40 years) field experiment with either no-tillage (NT) or plow tillage (NT) at three N fertilizer rates (0, 168, and 336 kg ha-1) and continuous maize (Zea mays L.). We used PCR-denaturing gradient gel electrophoresis (DGGE) to analyze the archaeal amoA gene, as a measure of the changing AOA community. Tillage rather than N fertilizer played a dominant role affecting the AOA community. Tillage and the interaction of tillage and sampling season had significant influence on AOA diversity. In winter, AOA were more diverse in NT than PT. Fertilizer rate did not significantly influence AOA diversity. However, sample season and N fertilization had selection function on AOA composition. Unique groups were discovered in different treatments, demonstrating the selection from tillage, fertilization, season, and/or their interactions. The significant tillage regulation of AOA provides a new clue to discover which environmental factors influence the AOA community and to explore its ecological significance in agricultural land.