Unearthing evidence: Researchers examine processes that support soil health

November 15, 2018, Kansas State University
Pavithra Pitumpe Arachchige, Kansas State University postdoctoral fellow, worked with Ganga Hettiarachchi, Kansas State University professor of agronomy, to collect spectromicroscopy data at Lawrence Berkeley National Laboratory and Canadian Light Source. The researchers applied an uncommon technique to soil samples and found direct evidence that management practices affect carbon sequestration in agricultural soils. Credit: Kansas State University

Healthy soil contains carbon—and a mystery. Some carbon remains in the soil for millennia, but some decomposes quickly and escapes into the atmosphere.

The latest research from Ganga Hettiarachchi, Kansas State University professor of and environmental chemistry in the department of agronomy, is helping scientists solve this mystery.

Scientists who want to keep in the soil previously thought that some types of carbon were more stable than others, but recent work has suggested that all carbon is degradable. Hettiarachchi and her research team have applied a new technique to studying soil chemistry and found direct evidence that the surrounding environment and management practices heavily influence soil carbon stability.

Their study, "Sub-micron level investigation reveals the inaccessibility of stabilized carbon in soil microaggregates," is published in Scientific Reports, a Nature research journal.

Hettiarachchi led a team that mapped chemical information in tiny soil samples by adapting imaging and analysis techniques used in other fields, such as material and biological sciences. Using scanning transmission X-ray microscopy coupled with near edge X-ray absorption fine structure spectroscopy, known as STXM-NEXAFS, for soil—plus analyzing the data—was challenging, but it provided simultaneous gathering of both spatial and chemical/physical information. Hettiarachchi said the years-long project yielded worthwhile results.

Ganga Hettiarachchi, Kansas State University professor of agronomy, and her research team collected spectromicroscopy data at Lawrence Berkeley National Laboratory and Canadian Light Source. Credit: Kansas State University
"We know soil has the potential to be a 'sink' for carbon," she said. "Understanding the mechanisms of carbon storage, or sequestration, can help us choose management practices that encourage ."

Carbon sequestration helps farmers maintain soil health and productivity and protects against climate variability. Hettiarachchi's study found that no-till management practices and crop rotations helped protect carbon in the soil in the long term. The researchers used soil samples that came from Brazil, a tropical agroecosystem, under these management practices for a period of 25 years. Preparing samples required saturating them with water, snap freezing them with liquid nitrogen, cutting them with a diamond knife and then taking them to collect spectromicroscopic data at Advanced Light Source in Berkeley, California, and Canadian Light Source in Saskatoon, Saskatchewan. The team used traditional bulk soil analysis techniques to complement their results.

"Although it was challenging, the technique we used is a very powerful technique," said Pavithra Pitumpe Arachchige, a postdoctoral researcher who worked on the project with Hettiarachchi as a doctoral student. "We were able to image and study the composition of very small soil aggregates with preserved natural conditions."

"Applying novel techniques to soil carbon chemistry provides a better understanding of the role the soil microbiome plays in the fate of soil carbon," said Chuck Rice, university distinguished professor of agronomy. "Carbon is key to soil health and the environment."

The group also is studying Kansas soils and has more publications coming soon. Hettiarachchi said testing soil from contrasting climates and agroecosystems was important because tropical environments encourage rapid degrading of soil carbon.

"Even there, certain and complex help," she said.

Explore further: What sleeps under the forest

More information: Pavithra S. Pitumpe Arachchige et al. Sub-micron level investigation reveals the inaccessibility of stabilized carbon in soil microaggregates, Scientific Reports (2018). DOI: 10.1038/s41598-018-34981-9

Related Stories

What sleeps under the forest

October 16, 2018

A largely unknown terrain begins not so far below the surface of the forest floor. While the processes in the top 30 centimetres of the soil are well known, deeper areas of the soil are the focus of a research group led by ...

Carbon sequestration not so simple in biomass crop production

February 21, 2014

Findings at the U.S. Department of Agriculture (USDA) are providing information about the soil carbon dynamics that play a crucial role in lifecycle assessments of bioenergy production. These studies at the Agricultural Research ...

Recommended for you

Sierra snowpack could drop significantly by end of century

December 11, 2018

A future warmer world will almost certainly feature a decline in fresh water from the Sierra Nevada mountain snowpack. Now a new study by the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) that ...

A glimpse into future oceans

December 11, 2018

Something peculiar is happening in the azure waters off the rocky cliffs of Ischia, Italy. There, streams of gas-filled volcanic bubbles rising up to the surface are radically changing life around them by making seawater ...

Slow flow for glaciers thinning in Asia

December 11, 2018

Providing water for drinking, irrigation and power, glaciers in the world's highest mountains are a lifeline for more than a billion people. As climate change takes a grip and glaciers lose mass, one might think that, lubricated ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.