Exploring rhizosphere nitrogen dynamics and losses: A comparative study of NUE in maize
Date
2024-08
Authors
Sterinbach, Samuel
Major Professor
Advisor
Castellano, Michael
Halverson, Larry
Emmett, Bryan
Howe, Adina
Committee Member
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Abstract
Excessive agricultural nitrogen application contributes significantly to environmental degradation through the release of nitrous oxide and the transport of nitrogen to major bodies of water. Methods to reduce the nitrogen lost to the environment include better synchronizing the plant's needs with the application and increasing the plant's ability to access nitrogen. This project examined high Nitrogen Use Efficiency (NUE) maize lines, which had significantly greater yields under low nitrogen applications than retired industry standards. We hypothesized that high NUE lines would have higher gross rates of nitrogen transformations than non-high NUE lines while minimizing the net nitrate (highly mobile) in the rhizosphere that could be lost to the environment. To investigate the high NUE plants at different historical fertilization levels, we collected data of nitrogen pools and fluxes and the rhizosphere recruitment of the plants with a focus on ammonifiers, ammonia oxidizers (the rate-limiting step in nitrification), and nitrifiers. Our research found that at higher fertilization levels, some of the high NUE lines trended to a lower estimated ammonia oxidizer abundance than the non-high NUE line. Additionally, at higher fertilization levels, high NUE lines had greater nitrate and ammonia concentrations in the rhizosphere than the non-high NUE line while maintaining similar shoot biomasses. Overall, these results provide strong evidence that NUE could be related to the preservation of NH¬4+ through selection against ammonia oxidizer. These results bring us one step closer to understanding the complex interactions between plants, soil, and the microbes present to reduce nitrogen loss from the system for a more sustainable future.
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