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Tech Makes Soybeans Sizzle

By: Gil Gullickson

Some farmers typically consider soybeans a sickly sibling to corn.  Well, perception is reality. If you treat soybeans like a lesser crop, the legume's yields will always trail those of corn. 
Shaun Casteel has a better idea. “Think of soybeans as equal to corn,” says the Purdue University Extension agronomist. When you team the smart use of technology with good management, soybeans do well, he notes.  Soybeans particularly scored high in droughty areas in 2012.  “Corn yields weren't good around here, but soybeans in good fields did well,” says Robert Wehr, who farms near Sigourney, Iowa, with sons Erik and Nick, and daughter Jill Landgrebe. “We had an abundance of pods early on, but there was little in them until we got a shower of rain in August. That really made the bean crop.”

Weather is an unknown for 2013. Still, rotating soybeans with corn and giving them equal billing can bode well for your bottom line. They don't even have to be rotated equally with corn.  “A corn/corn/soybean rotation is a good compromise,” says Jeff Coulter, University of Minnesota Extension agronomist.

University of Illinois trials from 2004 to 2007 with 12 site-years showed soybean yields after two years of corn were 6% higher than those in a corn/soybean rotation. Meanwhile, soybeans complemented corn yields. Although second-year corn yields fell 7% compared to first-year corn, the drop-off was not as steep as the 10% dip in continuous corn. “And whenever corn followed soybeans, yields were higher,” Coulter says.

Variety selection is key
Obtaining these yield gains hinges, to a large degree, on variety selection. Molecular marker breeding technology has turned out some high-yielding soybean varieties in recent years. The trick is to find out which varieties yield best on your farm. Not all soybean varieties are high yielding.  “Our trials have shown a 6-to 12-bushel-per-acre difference from the highest to lowest yielder,” says Casteel. “So start with genetics for the highest yield potential and yield consistency.”

Yield potential is the top consideration for the Wehrs when they pick soybean varieties. “Emergence, standability, and whether they adapt to no-till are also important,” Wehr says. 
Disease tolerance is another factor the Wehrs eye. Last year's drought provided a respite from sudden death syndrome (SDS), a fungal disease prone to wet spring weather that can obliterate soybean yields up to 100%.

“When we saw SDS in southern Illinois in 1983, we didn't know what it was,” says Don Schafer, DuPont Pioneer senior marketing manager. Now, this fungal disease has expanded to a point where it is in the central Red River Valley of North Dakota and Minnesota, he says.

Tech for SDS tolerance
Unlike insects, there are no traits that resist soybean diseases. In SDS's case, part of the difficulty in creating a truly resistant variety is that it's a multigenic disease. It's easier to create tolerance. Although this doesn't stop SDS in its tracks, it alleviates symptoms and reduces its impact on yield.

What are new soybean diseases that are cause for concern?

To find out more, go to www.agriculture.com/getintouchwithcroptech.

Developing transgenic disease-resistant soybeans is possible. “Some genes could work for SDS resistance,” says John Soper, DuPont Pioneer vice president of crop genetics and research development. “The challenge is the high cost to bring it through the regulatory process and then weighing that against the benefit to growers. It makes it difficult to go down that path for diseases that are regional in nature like SDS and white mold, given that we have plenty of native traits (for tolerance) for both.”   For now, fighting SDS entails a combination of tolerant varieties and cultural practices like planting date.

“There has been a big push for early-planted beans,” says Casteel. “We may have pushed them a little too much. SDS comes in with cool, wet soils in the early vegetative stage.”

A solution: target fields with SDS history at the end of planting, he advises.

Watch for SCN
One way you can ease the chances of SDS surfacing in your fields is to monitor your fields for soybean cyst nematodes (SCN). This stealthy pest can steal up to 30% to 40% of your soybean yields without you knowing it.  “SCN is usually present in fields with SDS,” says Greg Tylka, Iowa State University Extension nematologist. “SDS symptoms develop earlier in plants infected with SCN.”

SCN-resistant soybeans still work well to curb the pest. Concerns exist regarding SCN–resistant varietal performance due to overreliance on the PI 88788 resistance source. It's important to note these varieties still work well in most cases.

100
The percentage of soybean yield loss that can occur under the most severe Sudden Death Syndrome infestations.

“Soybean varieties with the PI 88788 source of resistance can still yield well and can prevent the buildup of SCN numbers, even in a field with SCN populations reproducing on PI 88788 varieties,” says Tylka.

To forestall any chance of resistance to SCN-resistant soybean varieties, Tylka recommends taking these actions:

• Rotate with nonhost crops like corn.

• Rotate to soybeans with other sources of SCN resistance other than PI 88788, if possible.

• Rotate to different SCN-resistant varieties with PI 88788 resistance. “The resistance still has four to five different genes, so not all PI 88788 varieties are the same in how they control nematodes,” says Tylka.

New SCN technology
Industry is developing transgenic traits to resist SCN.  “We have introduced traits into soybean plants and put them in traits for the past two years,” says Brian Vande Berg, Bayer CropScience senior scientist for corn and soybean research. “They have reduced cyst counts on roots and reduced SCN egg counts in soils. These results lead us to believe these traits are effective toward controlling soybean cyst nematode.”

The trait targets just SCN and not beneficial nematodes.

BASF and Monsanto are collaboratively developing an SCN-resistant transgenic trait. “Our focus is on broad-spectrum soybean cyst nematode resistance,” says Peter Eckes, president of BASF Plant Science. 

No timetable has been established for both traits. They may appear later this decade, pending regulatory approval.

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