What is the soil microbiome?

Have you heard of the gut microbiome? Or do you take probiotics? And did you know that the common antibiotic, Streptomycin, was discovered in the soil?

The soil is home to the world’s greatest biodiversity. That biodiversity includes insects that live in the soil–like ants and nematodes. It includes the world’s largest terrestrial organism–a fungi (for more on that, read this Soils Matter blog post ). And it includes bacteria like the Streptomyces family. The combination of bacteria and fungi is known as the soil microbiome.

grass, soil and roots
Soil microbes living under your turfgrass help your grass get nutrients, and contribute to the world’s largest collection of biodiversity. Credit: SV Fisk.

The health of the soil microbiome can affect the health of the plants living in it. Many of the worst diseases in crops or other environments are linked with changes in the soil microbiome. And many of the changes made in soil affect both the soil microbiome and the plants that live in them.

There is also a lot of interest in the management of helpful plant-associated organisms as allies to keep plants healthy and fight against disease and pests. Many microbes have long been appreciated for their ability to help plants stay healthy, either through better nutrition or defense against diseases.

To give you an idea of the variety and number of microbes in the soil, one of my research team’s projects at Washington, D.C.’s National Mall studied the soil microbiome under the grass. In that study, we found that bacteria that break down nitrogen in the environment were heavily present. Over 1,600 different species were detected just in that small area!

Just like humans live in towns and cities where people cooperate, soil microbes rarely act alone. They normally occur as populations within complex communities, the soil microbiome. The research project that my team worked on studied what would happen to the soil microbiome when that community was changed.

national mall grass in washington, dc
U.S. National Mall lawn area facing the Washington Monument during renovation of the lawn. Photo credit Joseph Roberts.

Due to planned renovations at the National Mall in 2010, we had a great opportunity to look at the soil microbiome before and after renovations. We hypothesized that changing the turfgrass system during renovation would also change the soil microbiome. We analyzed the soil before and after renovation. To our surprise, the imported turf from New Jersey, installed after renovation, did not significantly alter the soil microbiome!

The soil microbiome affects our food supply, too. Agricultural areas and other natural spaces are highly vulnerable to changes. Microbiomes offer a new and almost entirely untapped opportunity to influence interactions among plants and microbes to improve plant productivity and health.

Answered by Jo Anne Crouch, USDA-ARS

To read more about Crouch’s research, visit https://soils.org/discover-soils/story/soil-microbes-persist-through-national-mall-facelift

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