Heavier rain, drought and hotter days challenge SC's peanut industry

by Caitlin Looby (Climate Central) and Sonya Stevens (ABC News 4)

This story was produced through a collaboration between News 4 in Charleston and Climate Central, a nonadvocacy science and news group.

Johnny McMillan has noticed that summers on his 600-acre farm in Colleton County are getting hotter. That, with worsening bouts of heavy rain and drought, are making it harder and more expensive to grow peanut plants in South Carolina - one of America's main growing hubs for the popular legumes.

"Our summers are hotter than they used to be, but as long as you get some rainfall we do okay," said McMillan, who grows peanuts, cotton, corn and sometimes soybeans. "You want plenty of rain but you don’t want it just bogging down wet all the time."

Summertime averages in South Carolina’s Lowcountry counties have warmed nearly 2F since 1970 and the frequency of extreme heat days are on the rise. During the next few decades, hotter summers and intensifying rainfall threaten to reduce yields of the important crop - a challenge that experts are aiming to manage through special crop breeding approaches.

Warming temperatures are also causing rain to fall more heavily, creating conditions that are ripe for the fungal pests that plague McMillan's peanut crop.

"If it gets really wet you can’t spray, and disease gets away from you," he said.

Sruthi Narayanan, an associate professor at Clemson University who studies how climate change impacts crops, is among the researchers working with plant breeders to create new varieties of peanut plants that will be more resilient to the effects of heat-trapping pollution.

Summertime averages in South Carolina’s Lowcountry counties have warmed nearly 2F since 1970 and the frequency of extreme heat days are on the rise. (WCIV)

"Climate change is now impacting our crops, like peanuts, in a very serious way," Narayanan said.

More than 5.5 billion pounds of peanuts were produced last year in the U.S. and South Carolina is a top producer of peanuts. Peanut production is a growing industry in South Carolina, generating nearly $73 million last year. The state ranks sixth for peanut growing in the U.S. after Georgia, Alabama, Florida, North Carolina, and Texas.

Calhoun, Orangeburg, and Hampton counties were the top producing counties in South Carolina last year. Colleton and Dorchester counties are two other counties in the Lowcountry known for high peanut yields.

McMillan said his farm's peanuts are planted in May each year, and harvests start in October and end in the middle of November.

There are three kinds of peanuts grown in South Carolina: Virginia, Valencia, and Runner. Virginia, nicknamed "ballpark", and Valencia are the ones best for boiling and roasting. Runner peanuts become peanut butter.

Peanuts are an important crop in the U.S. because they provide plant protein. They are also a major oil seed crop.

According to Narayanan, peanuts are regarded as a climate smart crop because all parts of the plants can be used. There is the nut that people eat and the other parts of the plant can be added back to the soil to increase organic matter, which helps plants grow and keeps the soil moist.

Peanut plants are legumes, meaning they form seeds within a pod or the "shell" that winds up on the concrete floor at a baseball game. Legumes also help other crops by adding nitrogen to the soil. Peanut plants need conditions that are "just right".

The plants are grown in low rows and will flower a few weeks after they are planted. The plant can pollinate itself, and after that the pods will fill with seeds underground. Pod filling is the most important part because that creates the peanuts that people consume, according to Narayanan.

While peanut plants can grow in a wide range of temperatures, flowering and pod filling can only happen with a small temperature window. Any warmer and the plant will suffer from heat stress, stunting plant growth, and damaging the quality of the peanut. They also need a lot of water during this time, but not too much.

Narayanan said rising heat is the stressor that is most problematic, while McMillan said heavier rain is his biggest challenge. Farmers can irrigate or water more during drier times, but there isn't a lot they can do when temperatures are too hot.

One solution is to develop new varieties of peanut plants. And that's what Narayanan does. She works with plant breeders to figure out which genes will help make peanut plants more tolerant to heat.

It can be tricky work. Not only are there lots of genes to look at, but Narayanan has to make sure they're modifying ones that will be passed onto future generations. Her goal is to create new varieties of peanuts that can withstand hotter temperatures, but also can breed under a wider range of temperatures.

As for the changing weather, McMillan is hopeful that science will continue to help South Carolina's peanut industry meet the demand.

"The technology that has gone into seed production and development has really helped us with yields," McMillan said, adding that they are always looking for better varieties. "We do a lot better with just about all crops than we did 50 years ago."