Standing in the middle of a windswept Red River Valley farm field, North Dakota State University researcher Caley Gasch explains how emerging soil carbon markets are driving the need for more accurate soil carbon measurements.
"The stakes are really high for the farmer,” said Gasch. “And they deserve really good quality carbon estimates, if their livelihoods are going to be based on those measurements."
Carbon dioxide, a heat-trapping, greenhouse gas linked to climate change, can escape into the atmosphere when soil is disturbed by tilling and other practices.
Companies have sprung up to pay farmers to store carbon by not tilling their soil and by planting cover crops. Those companies then sell that stored carbon as a credit to other businesses who want to offset their greenhouse gas emissions.
But businesses also want detailed proof that their payments are working to reduce carbon emissions.
Researchers at the farm near Leonard, N.D., use a truck-mounted, four-foot-long hydraulic probe to pull soil samples from a field. It’s a common method for sampling soil, but dozens of samples might be needed to accurately assess a field.
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Scientists know how to precisely measure carbon in a soil sample.
But accurately measuring carbon — and changes in the amount of carbon across an entire field — is much more complicated because carbon is constantly cycling through the soil.
“We need more efficient and less labor-intensive ways of taking lots of carbon readings within a field,” said Gasch.
Gasch is working with postgraduate student José Pablo Castro Chacon to combine a variety of data, from drone and satellite images to precise crop yield data from fields, to create maps that will pinpoint the best places to sample a field for carbon.
“So that we can take the fewest samples possible but maximize the amount of information and representation that we get from the field,” she said.
As part of the project, Gasch is also testing the accuracy of new smart technologies that can estimate soil carbon without having to remove a soil sample. The data she collects can also be used to improve the accuracy of the new testing tools.
Improving accuracy and reducing cost of carbon testing might be a key to convincing more farmers to try carbon markets.
A recent survey by economists at Purdue University found only about 2 percent of farmers surveyed had discussed carbon markets with a company offering payments.
While there are well-established scientific methods for measuring carbon in soil, there are no standards for carbon markets, and companies are using a range of assessment tools.
“It feels like the wild west to me right now," said University of Minnesota soil health specialist Anna Cates. Carbon has been used to describe soil health in the past, said Cates, but trying to track carbon as a single component in a complex ecosystem creates a lot of room for error.
“Carbon is messy. It’s heterogeneous across the landscape,” said Cates. “So how we sample can really affect whether we see changes or not, but the markets want to see a certain level of certainty if they're going to pay for changes in practices."
While few farmers are signing contracts for the carbon market right now, there is growing interest.
“Questions are certainly coming up. I hear it from crop advisors. I hear it from farmers. My extension colleagues are getting questions. This is definitely on people’s minds," said Cates.
Caley Gasch hopes her team’s research will help answer some of the questions and give farmers more assurance carbon markets will treat them fairly.