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Scientists look for crops that help amid saltwater intrusion

A partially brown field of crops
David Boraks
Brown areas in a field in Hyde County, in eastern North Carolina, show the effects of saltwater intrusion. Scientists at NC State University have been experimenting with salt-tolerant crops to help farmers there.

This story appeared first in WFAE's weekly climate newsletter, which is out Thursdays. Sign up at WFAE.org/newsletters.

Saltwater intrusion and sea-level rise are growing problems for farmers in eastern North Carolina, especially in counties on the Albemarle and Pamlico sounds. And it’s only expected to get worse with climate change.

Farmers have to adapt. That can take several forms: Installing tide gates to hold back the saltwater, taking some land out of cultivation with help from government conservation funding, and planting salt-tolerant crops. When it comes to crop choices, the question is which are both able to withstand the salt and be profitable?

Cotton, for example, can make money where wheat, corn and other vegetables won't grow, according to farmers I've spoken to in Hyde County, right on the Pamlico Sound. Now a new study from North Carolina State University finds that some soybean varieties could work, too.

Andrea Gibbs, the agricultural extension agent in Hyde County, recently joined colleagues at North Carolina State University in a study to figure out which soybean varieties are most salt tolerant, which she refers to as "salt excluders."

She remembers hearing about the problem when she arrived in Hyde County nine years ago.

"I would have farmers call, and there would be an area in the field that they had lost, you know, had a decrease in production. And they were pretty sure that it was saltwater intrusion. But I would go and take soil samples and kind of assess their levels," Gibbs said.

Saltwater gets into the fields through creeks and drainage canals. And it gets swept onto the land in tidal surges that come with more intense storms.

She sought help from colleagues at NC State, but there were no studies. And getting funding was difficult, because the problem seemed isolated to a few areas. Finally, in 2021, with help from a private financial donor, she and her colleagues were able to do a large-scale field trial of soybean yields at one farm.

Gibbs and her colleagues found a field with just the right mix of light and serious salt damage and planted four varieties — one regular soybean variety that's not salt-tolerant and three other varieties that were. They planted all four varieties in eight plots with varying degrees of saltwater intrusion.

The results were dramatic.

"In those areas where it is just super salty, it didn't matter what soybean you planted, it didn't come out of the ground," Gibbs said. "But the salt excluders did help in those moderately salty areas. The yield was still not near what the farmer would like it to be, but they are helpful."

Gibbs and her colleagues shared the study in the September-October issue of the NC State Economist. They wrote: "In general, the use of salt-tolerant soybean varieties can help mitigate the potential profit-reducing impact of low-to-moderate levels of saltwater intrusion."

Co-author Rod Rejesus, an NC State professor and agricultural extension specialist, cautioned that the study covered just a single year and said more data is needed to bolster their conclusions.

But based on that data, he said, "We found that there's essentially a sweet spot for salt-tolerant varieties. Of course the cost of these types of seeds is a little bit higher. But I think the important take-home message from our studies is that it's not a panacea for extreme saltwater intrusion."

The worse the salt contamination gets, the harder it will be to grow and make a profit, he said.

This is just one small study in one county, but it's the kind of information that farmers need as they battle climate change, Rejesus said.

"Saltwater intrusion and climate in particular is just affecting productivity of the agricultural sector," Rejesus said. "If you believe that food is important in our economy, and the agricultural sector is a big part of it, of course, and there is a need to understand (this), in my mind, what's the damage if we don't adapt?"

RELATED VIDEO: "Fighting Saltwater Intrusion in the Blacklands," PBSNC, April 19, 2023

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David Boraks previously covered climate change and the environment for WFAE. See more at www.wfae.org/climate-news. He also has covered housing and homelessness, energy and the environment, transportation and business.