Soybeans — Looking For Ways To Get The Yellow Out
Could planting oats along with soybeans help to get the “yellow” out?
It’s one method that is being studied to reduce the severity of soybean iron deficiency chlorosis (IDC). “A lot of research has been done on this,” says University of Iowa soybean expert Palle Pedersen, “and there are no good solutions yet, except variety selection.”
There has been extensive research on applying iron seed coatings, foliar sprays and fertilizers to correct iron deficiency. But the results have been inconclusive, says Dave Franzen of North Dakota State University (NDSU), “sometimes they work, sometimes not.”
Matt Mechtel, who grows soybeans in southeast North Dakota, tried chelated iron applications and a number of other “witches brew” to fight IDC. But the effects were only temporary, he says. Iron treatments are expensive, too – costing up to $20/acre. “It’s not practical, currently,” says George Rehm, University of Minnesota retired soil nutrient specialist. “We don’t recommend it.”
NDSU is now looking at slow-release iron fertilizers, which could supply soybean plants with iron for an extended period, says soil scientist Jay Goos, of NDSU. However, developing resistant varieties is the main focus of both public and private IDC research. “Progress has been made,” says Franzen. Still, only about one in 10 new soybean cultivars tested at NDSU shows a high level of IDC tolerance, he says. “We’ve got a lot of work to do in breeding.”
A link to nitrates?
Scientists are also trying to unravel some of the lingering mysteries connected with IDC. For instance, why does planting more thickly reduce the severity of IDC? And why do soybeans growing over wheel tracks stay green in wet years when the rest of the field turns yellow?
One theory is that IDC is related to soil nitrates, Rehm says. That’s what led to the idea of planting oats along with soybeans. The small grain uses up nitrogen and dries out wet soils early in the season. Later, the companion crop is killed with Roundup. Rehm is now leading multi-year field trials in Minnesota and the Dakotas to test this technique.