Beneath our feet, a world of microbial life powers the health and productivity of crops. But when that microbial life is disrupted especially in high-value growing systems like high tunnels it often takes time to recover. A Penn State research team led by Laura Kaminsky, who at the time was a doctoral candidate, and supported by former Penn State faculty member Terrence Bell, helped farmers understand how to rebuild this critical underground ecosystem more effectively.
Their findings, first published in Environmental Microbiology in 2021, laid the foundation for future guidelines that could improve soil health, crop yield, and long-term sustainability in high tunnel agricultural systems.
High Tunnels: Productive but Problematic
High tunnels plastic, greenhouse-like structures that extend the growing season were widely used to grow tomatoes and other high-value crops. But these structures, while increasing productivity, created long-term challenges underground.
“Over time, soil quality in high tunnels tends to degrade,” said Kaminsky in a Penn State news story. “If the same crop is grown year after year, soil pathogens build up and cause increasing disease.”
To address that, farmers often relied on soil-clearing practices like fumigation, anaerobic soil disinfestation, or solarization. While these methods reduced harmful pathogens, they also wiped out the beneficial microbes that supported nutrient cycling and plant health.
How Soil Recovered—And What Slowed It Down
Kaminsky and Bell aimed to understand how soil microbial communities recovered after being cleared and how certain soil conditions might have slowed that process.
Their experiment, conducted at Penn State’s Buckhout Laboratory in 2018 and 2019, involved introducing unsterilized “source” soil into sterilized “recipient” soil, simulating natural recolonization. They then tested how two common high tunnel issues salt buildup and high nitrogen affect microbial regrowth.
The results were telling. Soils amended with salt or nitrogen showed a significantly delayed and less diverse microbiome compared to untreated soils. In other words, high salt and nitrogen conditions often found in high tunnel systems made it harder for beneficial soil microbes to return.
“It was not surprising that high salinity slowed things down,” said Kaminsky in a Penn State news story. “Salt is a major stressor for many microbes. But we were surprised that nitrogen something we think of as a nutrient also led to less microbial diversity. It seems to encourage only a narrow group of fast-growing microbes.”
Meet the “Universal Colonizers”
Despite the challenges, the team identified some hardy microbial survivors. After one week, the dominant microbes were members of the Bacillus and Paenibacillus genera both fast-growing, resilient groups known to thrive in a variety of environments.
By week seven, microbial diversity had increased, but these “universal colonizers” remained present across all conditions. Understanding which microbes bounced back first could eventually help researchers design soil additives or inoculants that support recovery.
Building Knowledge, Building Solutions
This research was more than just a scientific study it was a stepping stone to practical solutions for growers. With support from the U.S. Department of Agriculture and the National Science Foundation, Kaminsky translated her findings into educational resources for Penn State Extension to help farmers make informed decisions about soil management.
“Laura has worked hard to develop both leading-edge research skills and communication skills that allow her to relay the state of knowledge in our field to farmers and other stakeholders,” said Bell in a Penn State news story.
Long-Term Impact: Healthier Soil, Healthier Farms
The work conducted at Penn State helped pave the way for a new era of precision soil recovery one that could allow farmers to rebuild healthy microbiomes more efficiently after soil-clearing events. As high tunnels continue to play a role in meeting food production demands, this research offers a roadmap for maintaining fertile, productive soils for years to come.
By understanding not just what works, but why, Penn State researchers helped growers protect the long-term vitality of their land one microbe at a time.
Where Are They Now?
Laura Kaminsky is currently a research scientist at Pasa Sustainable Agriculture. Terrence Bell is now a faculty member at the University of Toronto – Scarborough. His group is currently focused on developing microbial probiotics for agriculture than can survive predictably under a wide range of conditions, as well as understanding the potential for enhancing microbial contributions to crops in urban agriculture settings.
While at Penn State, Kaminsky developed Penn State Extension programs to share the study’s results with growers. Paul Esker, assistant professor of epidemiology and field crop pathology, was also involved in this project.
The research was funded by the U.S. Department of Agriculture Organic Transitions Program, the USDA-National Institute of Food and Agriculture, and the National Science Foundation Graduate Research Fellowship Program.
Source : psu.edu