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The influence of alfalfa-switchgrass intercropping on microbial community structure and function
Gyuhyon Cha1, Kelley A Meinhardt2, Luis H Orellana1
1School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
Environmental Microbiology
|September 23, 2021
Summary
Intercropping switchgrass with alfalfa, a nitrogen-fixing cover crop, offers a sustainable alternative to synthetic nitrogen fertilizer. This practice promotes soil microbial community changes beneficial for nitrogen preservation.
Area of Science:
- Agricultural Science
- Soil Microbiology
- Environmental Science
Background:
- Nitrogen fertilizer use in bioenergy crops like switchgrass incurs costs and environmental risks, including nitrogen leaching and nitrous oxide (N2O) emissions.
- Intercropping with nitrogen-fixing plants, such as alfalfa, is a potential sustainable alternative, but its impact on soil microbial communities is not well understood.
Purpose of the Study:
- To investigate the effects of synthetic nitrogen fertilization versus intercropping with alfalfa on the soil microbial community functionality in switchgrass agricultural systems.
- To compare the soil microbial responses to fertilization and intercropping over two growing seasons.
Main Methods:
- Analysis of 24 metagenomes from the upper soil layer of agricultural fields under three treatments: unfertilized switchgrass (control), fertilized switchgrass, and switchgrass intercropped with alfalfa.
- Utilized quantitative polymerase chain reaction (qPCR) data for specific microbial groups.
Main Results:
- Neither synthetic fertilization nor intercropping caused major shifts in overall microbial community taxonomic or functional composition.
- Both intercropping and fertilization led to increased abundance of mycorrhizal fungi and ammonia-oxidizing archaea and bacteria.
- A significant correlation was observed between the abundance of betaproteobacterial ammonia-oxidizing bacteria in fertilized plots and N2O emissions.
Conclusions:
- Short-term intercropping with alfalfa induces minor but significant shifts in soil microbial communities, favoring nitrogen preservation.
- Intercropping emerges as a potentially viable and environmentally sustainable alternative to synthetic nitrogen fertilization in switchgrass cultivation.
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