RESEARCHER: Dr. Elizabeth Maga, UC Davis, 2020

KEY TAKE-A-WAYS

• Understanding the nitrogen-fixing capacity of microbes in manure can lead to the development of strategies that either enhance or reduce bacteria related to the nitrogen cycle. This will allow dairy producers to improve the management and fertilization potential of manure. 

• Researchers from UC Davis identified a microbe found in commercial dairy cow manure, Prevotella bryantii (P. bryantii), that was able to grow in a nitrogen-limited media, suggesting it may be able to fix nitrogen.

• More research is needed to understand the nitrogen-fixing capabilities of P. bryantii and to identify other potential nitrogen-fixing bacteria in dairy cow manure. 

BACKGROUND, OBJECTIVES, FINDINGS AND OUTCOMES

Nitrogen-fixing bacteria can transform nitrogen gas from the atmosphere into fixed nitrogen compounds, such as ammonia. Specific microbes involved in the nitrogen cycle could be present in dairy cow manure and play an important role in controlling the concentration and form of nitrogen in manure. Understanding the nitrogen-fixing capacity of microbes in manure can lead to the development of strategies, such as dietary manipulation or manure treatment plans, to either enhance or reduce bacteria related to the nitrogen cycle. This will allow dairy producers to be better stewards of the environment and improve the fertilization potential of manure.

Previous CDRF-funded research performed at UC Davis identified potential nitrogen-fixing microbes in dairy cow manure. The goal of the current study was to test the nitrogen-fixing capabilities of one of these hypothesized strains, the bacteria P. bryantii. 

To further test the nitrogen-fixing capabilities of P. bryantii, researchers planned to conduct additional tests including chemical assays and gene expression techniques. Unfortunately, COVID-19 restrictions on research and staffing made some aspects of testing impossible to complete. The initial findings from this discovery process are promising, but require follow-up to capture conclusive results.

There are indications that P. bryantii is capable of fixing nitrogen, but the specific actions of this microbe need to be definitively demonstrated. Such a discovery could enable the development of strategies such as dietary manipulation or post-excretion treatment technology to increase or decrease the presence of microbes related to the nitrogen cycle. 

Further study is required to determine how nitrogen-fixing microbes can be enriched in manure, or manipulated to increase their nitrogenase activity, with the goal of improving the fertilization potential of manure.