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How to Battle Iron Chlorosis in Soybeans
North Dakota and northwestern Minnesota may not seem like soybean country. Dig a bit deeper, though, and you’ll find the area is a thriving hub for this hardy legume.
“Soybean acres continue to move north,” says Alan Scott, DuPont Pioneer technical product manager. “Wheat would have been grown in the western half of Minnesota (and North Dakota) back in 1994. Now, a lot of those acres have moved to corn and soybeans.”
North Dakota soybean acres have mushroomed from around 750,000 acres in 1994 to 6 million acres in 2014.
“Cass County (the east-central North Dakota county that borders Minnesota) has the largest soybean acreage of any county in the U.S.,” says Scott. “This has been a trend for the past 20 years and frankly, I don’t see it changing. It has displaced wheat due to economics.”
Scott and other DuPont Pioneer scientists met with agricultural reporters this week on a tour of the company’s soybean research facilities in the Midwest.
The Upper Midwest isn’t just soybean country, though. It’s also chlorosis country, with soybean plants riddled by the iron chlorosis calling card of chlorotic leaves and stunted plants.
A frustrating factor for managing iron chlorosis is that there’s no one factor that causes it.
A combination of factors like soil pH and calcium carbonate salts contribute to the malady, says Scott. It also varies from location to location.
“Even in a field, areas will vary (for iron chlorosis),” says Scott. “That is what it makes it tough to characterize.”
Dry weather worsens iron chlorosis, says Scott. “If weather is on the dry side, you don’t get that flushing of the calcium carbonates. Since we were dry earlier this spring, we are seeing higher-than-normal iron chlorosis, especially in west-central Minnesota.”
Enter Tolerant Varieties
Planting soybean varieties that tolerate iron chlorosis are the best way to deal with the malady. DuPont Pioneer rates varieties that tolerate iron chlorosis on a scale of 1 to 9. The higher a variety ranks on the scale, the better it tolerates iron chlorosis.
“If you have a rating of 8, you will see (tolerance) performance, regardless of location,” says Nadia Krasheninnik, a DuPont Pioneer research scientist.
Molecular marker technology has helped develop varieties that tolerate iron chlorosis with no yield drag. Molecular markers are DNA regions that can be associated with different genes and traits, note DuPont Pioneer officials. Scientists rapidly screen for markers to pick traits faster than possible with traditional breeding and speed product development.
“It also gives us the ability to cut through the misconception that some varieties with iron chlorosis tolerance had a bit of yield drag,” adds Scott. Yield drag doesn’t exist with these varieties, he notes.