Why is Praerieboden fertile

Insight into a submerged world of microbes

To the farmers who came to the prairies of North America, the land seemed like a paradise: fertile soil that just seemed to be waiting to be plowed under. This was especially true of the Tallgrass Prairie. This is the prairie that grows dozens of types of grass that can grow up to a man:

"The tallgrass prairie stretched from Canada to Texas, from Illinois to Nebraska. It was tremendously productive and fed the huge herds of bison and the many other wild animals that lived there at the time. Today, this once rich ecosystem is very isolated,"

says Noah Fierer from the University of Boulder in Colorado. He is interested in the microbial communities in the prairie soil with a view to projects that want to restore this ecosystem in protected areas. Above all, he wants to understand how soil fertility works:

"Most of the prairie soil has been converted into agricultural land. We are interested in how this has changed the communities in the soil. Fertility is about more than nutrients and water in the soil: it is also determined by the microorganisms that live in it Life."

Noah Fierer and his team found 31 locations in the former range of the Tallgrass Prairie that were never used for agriculture. They took soil samples and sequenced the DNA of the microorganisms. Their diversity is surprisingly high:

"A special group of little-known bacteria is abundant in the soils of the Tallgrass Prairie: the verruco microbes, which appear to break down carbohydrates. Their preferring low-nutrient and slow-growing soils may explain why they are less common in agricultural soils It could also be that soil organisms such as roundworms play a role in their spread. We don't know for sure. "

Verruco microbes were dominant in all samples from the Tallgrass Prairie. That being said, the microbial community varies:

"There is a north-south gradient that seems to be influenced by the climate. Then we used a computer model to use the climatic variations in the Midwest to calculate how the microbial communities could have been distributed 100 to 150 years ago, before the prairie in Farmland has been converted. "

The new findings are important for saving the disappearing ecosystem, explains Noah Fierer:

"Now that we know which microorganisms once lived in the prairie floor, we can begin to change today's communities in this direction. In order to restore the Tallgrass Prairie ecosystem, it is not enough to put a few plants out, because too the soils were part of this ecosystem. We now have at least an idea of ​​what we actually want to reconstruct. "

The findings could also be used to make soils more productive without the use of fertilizers. This is also underlined by Mary Scholes from the University of the Witwatersrand in Johannesburg in her comment on the work of her colleagues, in which she was not involved:

"We used to think that to maintain soil fertility it was enough to add nutrients such as spices - like in a stew. But that's not true: the roots absorb what has been made chemically available by microorganisms in the soil."

In order to maintain soil fertility, it is essential to better understand the diversity of microorganisms in the soil.