Last summer Rich Jansen's soybeans grew taller than he is: 6 ft. 2 in. He and his wife Mary Ann farm near Tecumseh, NE, about 60 miles south of Omaha. The 6+-ft. soybeans helped Jansen reap his best yields ever.
“I've never seen soybeans grow quite so tall before and still stand well,” says Jansen, a Merschman seed dealer. “It was a Truman variety, which I've planted before. It has good standability and a good stalk. The only thing we did differently was put 5 tons/acre of chicken manure on it, and we ended up with 89 bu./acre on a 15-acre, pivot-irrigated field.”
On the other 285 irrigated acres that Jansen planted to Truman soybeans last year, yields averaged 58 bu./acre. The county average for dryland soybeans is about 26 bu./acre, he says.
“This just shows that if you have enough water and fertilize it right, you can make exceptional yields,” says Jansen. “Good drainage is also important,” he adds.
Jansen plants soybeans in 20-in. rows at a 185,000-plant/acre rate and sprays them twice with Roundup to control weeds. Except for the chicken manure, all his soybean fields were treated the same.
“There are 22 chicken houses near that field, so I just hauled the manure across the road and spread it,” says Jansen. “The nutrient analysis is 295 lbs./acre phosphate, 298 lbs./acre potash and 152 lbs./acre nitrogen (if it's worked into the soil right away). Plus, it has all the trace elements, like magnesium, sulfur, zinc and iron.”
Lodging became a worry when Jansen saw how tall the beans were growing. “Usually tall beans don't yield that well due to lodging, but everything was just right and we didn't get any big windstorms to knock them over,” he says.
TALL PLANTS CAN actually accompany high-yielding soybeans, points out Bill Wiebold, University of Missouri Extension agronomist. At least, that's what yield champions like Kip Cullers, Purdy, MO, are discovering when yields approach or surpass 100 bu./acre, he says.
Despite the apparent correlation between height and yield, soybean farmers shouldn't put top priority on finding a soybean plant that can grow tall, cautions Wiebold. What's really important is not so much the height of the plant, but the number of nodes on the plant, he explains.
“What typically happens across the Midwest when soybeans grow over 4 ft. tall is that the plants fall over,” says Wiebold. “When the plants lodge, the leaves aren't able to capture the sun, which reduces yield. So, not everyone should be shooting for 5-ft.-tall or taller soybeans.”
Yet, farmers who practice high-yield management and use newer genetics may be able to grow soybeans with a larger stem girth to reduce yield loss from lodging, adds Wiebold. “Cullers' beans also produce a thicker stem that helps them stay more upright,” he points out.
Poultry manure may be an important ingredient that helps both Cullers and Jansen produce a thicker stem that is less likely to lodge, notes Wiebold. “Surely, the nutrients and organic matter from chicken litter can help to create a high-yield environment for soybeans,” he says. “Yet, there's definitely a lot more to ensuring high yields than justselecting a tall-growing bean and fertilizing well.”
In addition to the dangers from lodging, there's another potential pitfall to growing extremely tall soybeans, says Jansen. “You need GPS equipment to keep from getting lost in the field,” he jokes, but as long as yields are approaching the 100-bu. range, it may not be the worst problem to have.