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Sunflower Provides Assist in Dealing With Salinity

Monday, October 24, 2016
filed under: Research and Development

Arnold Woodbury knows soil. Specifically, he knows the soil on his farm near Wyndmere, N.D. He’s been farming there

for decades—and if there’s one thing about his soil that stands out to him, it’s that soil here is often too wet, which means it often has high salt content. Woodbury, like many producers in southeastern North Dakota, knows that extra salt can make it tough to grow many crops. It’s one of the reasons he added sunflower into his rotation more than 40 years ago.
       “Sunflower works well in areas where we have saline seeps,” says Woodbury. “We have had spots that were white with salt. We’ve been planting sunflower and alfalfa there, and those crops helped turn those areas around. It doesn’t happen overnight, but I do think sunflower tolerates that soil the best and helps the soil structure.”
       Researchers are finding that to be true in the opposite corner of the state as well. Near Williston, in northwestern North Dakota, researchers have been watching a saline seep form over the past two decades at the southern edge of their dryland farm.
       “It’s been forming slowly over the past 20 years, but has quickened pace in the last five,” explains Dr. Clair Keene, area extension specialist at the NDSU?Williston Research Extension Center. “In August 2014, we installed groundwater monitoring wells with the help of the Montana Salinity Control Association. The purpose of those wells is to monitor water table depth over time. We’ve recorded readings there a few times in the past two years, and that initial data helped us form a reclamation plan.”
       The groundwater monitoring wells have helped Keene and her team outline the surface area contributing to the seep, called the “recharge area.” Now they’re working to plant different perennials in those areas.
       “Our reclamation plan was to plant as much land as possible into perennial forage. Perennials like alfalfa are the first choice for saline seep management because of their season-long growth and water use,” she says. “We need to increase water use in the recharge area and perennial forages use water the entire time possible. Over the winter, when the ground is frozen, the forages don’t do anything; but when temperatures warm up in the spring, the forages kick into action. If we use something like wheat, we don’t have something in the ground actively using water during early spring and late summer. We miss the opportunity to use water for months each year.”
       And, like Arnold Woodbury, the university researchers are starting to use sunflower to help manage the seeps.
       “Sunflower is a much longer-season crop than spring wheat or other small grains which are harvested in early August; growers plant sunflower in May but don’t harvest until September or October,” Keene points out. “Sunflower uses a lot of water in June and July and, depending on the maturity of the sunflower, will continue using water through August. Farther south, they could even use water into September. Sunflower is one of the best annual crops for maximizing water use over a season.
       “The deep roots on a sunflower plant are a huge advantage,” Keene continues. “Sunflower roots are five to six feet deep, sometimes as deep as eight feet. Compare that to small grains, like wheat, whose roots are shallow. They can go five feet deep, but three to four feet is more common. Even corn isn’t as deep as sunflower; root depth of corn is only about four to five feet.”
       Those deep roots help get the water out of the soil at a deeper level. Keene notes that sunflower is a saline-tolerant crop, meaning if it’s planted in a field with a large seep, sunflower would do better than other crops, including corn.
       “Of course there are differences among sunflower varieties,” she adds. “Producers should check with their seed dealers and find out which varieties are the most salt tolerant and appropriate for their growing area.”

       When it comes to varieties, research is being conducted there, too. Brent Hulke, research geneticist with USDA-ARS

Sunflower and Plant Biology Research Unit at Fargo, N.D., is working with a number of scientists from around the world on a research project funded by Genome Canada and the National Science Foundation. They’re looking at how salt, drought and flood conditions affect soil. Researchers started salt tolerance trials this year, looking at how different sunflower lines react to salty soil.
       “We’re starting to get some results of the first year of the trial,” says Hulke. “What we can tell at this point is that salt tolerance is real in sunflower. One field that we planted had some areas that were saltier than other parts. In the worst parts of that field, we didn’t even have germination. In the moderately salty areas of the field, we can see varietal differences.
       “One reason we have salty soils in the Dakotas is because of the wet cycle we’ve been in. That’s bringing deep soil salts to the surface. If this wet cycle continues, we may need to look at making this a breeding goal for the future. We want to stay ahead of future problems that can relate to uncertainties of climate change. We want to make more stress-tolerant crops—not just salt, but crops that are tolerant to many climate scenarios.”
       Hulke is hopeful the research he’s doing on the Canada project will provide some answers. His team is providing the plant breeding and field experimental design expertise for the whole project and will be working directly on flooding tolerance studies to discover genes responsible for improvement in seedling flooding tolerance. The project will identify and fully characterize the genetic basis of stress resistance in sunflower and create resources to give sunflower breeders from the public and private sectors access to stress-resistant, high-yield cultivars within four years of the project’s end. The team will also develop models to predict likely yields of the new cultivars in different soil and climate conditions.
       It’s the first time this type of research has been done on sunflower, and Hulke is hopeful it will help improve yield as well as oil content and seed size in sunflower grown in stressful conditions—all of which is good news for producers like Arnold Woodbury.

— Jody Kerzman