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ST. LOUIS (DTN) -- Year after year, the fertile, irrigated river bottoms of southeastern Nebraska have blessed Greg Peters with big, beautiful soybean plants.
A little too big, in fact.
"The beans have a tendency to get really tall, with a lot of space in their internodes," the DeWitt, Neb., farmer and chairman of the Nebraska Soybean Board of Directors told DTN. "In a windstorm, they're so tall or heavy with pods, they start leaning and tend to lodge really badly."
Just a couple years ago, one of Peters' fields spawned towering, 6-foot-tall beans in 15-inch rows. "You step out into a field like that and just disappear," Peters recalled. "You had to get on the back of the pickup to look over the top of the field or get up on the pivot to see what was going on out there."
Most of those beans toppled over before harvest. In what should have been a bin-buster field, Peters estimated that he lost 15 to 20 bushels per acre to lodging.
Fortunately, scientists from Purdue University and the University of Nebraska have isolated and cloned a gene that could help farmers like Peters in the future.
The gene, called Dt2, produces soybean plants that are semi-determinate, and therefore shorter. "With the shorter stature, there's less lodging potential," University of Nebraska agronomist Jim Specht explained to DTN. On average, Specht said the plants sport about 17 nodes, compared to the 22 or 24 nodes that current varieties can reach.
THE DETERMINATE FACTOR
Most beans in the United States are either determinate or indeterminate. Determinate beans are usually short and bushy, because they stop vegetative growth once flowering begins. Indeterminate soybeans continue growing throughout the season, even after reproductive stages are underway, so they tend to be taller.
Determinate beans are typically found in southern regions and in varieties from maturity group V and up, Specht noted.
The shorter growing season of more northern states requires the extended growing habits of indeterminate soybeans, and they are generally found in varieties from maturity group IV and earlier, Specht said.
"When we try to grow determinate varieties in the North, we only get about 12 nodes," he explained. "In the North, we have to combine our vegetative period with our reproductive period -- they have to overlap. In the South, with the longer season, they don't."
Ironically, the conditions that produce some of the best soybean yields -- irrigated fields, fertile river bottom soils, or a wet growing season -- can also produce overgrown indeterminate soybeans that are prone to collapse in windstorms or topple over from the weight of their own pods.
Narrow row spaces can contribute to the problem by forcing beans to grow up rather than out, Peters said. Widening his rows to 30 inches didn't tame the leggy legumes either. Come harvest time, the sprawling plants still cause a problem.
"They get tangled up in the row beside where you are trying to cut, and the row dividers on the outside of your header can't separate them," he said. "Then they pile up on the outside row dividers and they shatter out there when the reel goes around, so you have a yield loss."
A HAPPY MEDIUM
Using the Dt2 gene, UNL soybean breeder George Graef developed the first high-yielding semi-determinate soybean variety (named NE3001) for use in the northern U.S. several years ago. Since then, Specht said extensive university trials have shown that the Dt2 gene can produce a Goldilocks plant -- not too big, not too short, and with comparable yield.