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March 13, 2007

Variety selection for continuous beans is critical

WEST LAFAYETTE, Ind. - More growers are focusing on continuous corn because of the biofuels movement, but beans on beans could become more likely in areas where the corn yield potential is lowered, said a Purdue University expert.

"This focus on biofuels is causing a shift in production systems. In areas where a grower can continuously grow 200 bushels-plus corn, there may be a shift to continuous corn at least in the short run," said Shawn Conley, Purdue Extension soybean specialist. "However, in areas where the soils are poorly drained and the yield potential for corn is significantly less, we may see more growers focus on continuous soybeans."

As with continuous corn, growers planting beans on beans are going to have to make some adjustments to their crop systems to deal with various issues, Conley said.

Growers need to keep an eye on management issues related to weed control, spend more time selecting a soybean variety and rotate soybean varieties yearly to mitigate disease and nematode related issues.

"Herbicide selection will also be important," Conley said. "Growers should consider some form of residual product that offers an additional herbicide mode of action so as not to increase the risk of ghyphosate-resistant weeds."

Soybean variety selection also is critical to the success of growing continuous beans, Conley said. Growers should select varieties based on yield potential, maturity and field history (disease and nematode), he said. 

Indiana soybean producers currently are not diversifying their genetic pool and the yield potential to which they have access. "And that's really hurting growers," Conley said.

The benefits of diversifying the soybean genetic pool and planting different maturity groups come in the timeliness of harvest. Planting different soybean varieties and varying maturity groups also allows the soybean crop to avoid environmental impacts, such as drought, and acts as a balancing act to help increase overall yield potential, Conley said.

Not only is soybean variety selection important, but rotating these varieties to avoid susceptibility to pests and diseases is crucial, too.

For example, frogeye leaf spot is a disease that has appeared more frequently over the past two years in Indiana. If a grower planted a variety that is susceptible to frogeye and the disease moves in late in the season, the grower may not see a significant yield loss in the first year. The disease may overwinter in the soybean residue, causing a potential problem if the susceptible variety is planted in the same field the following season. Generally, the disease incidence comes earlier in the growing season and may cause significant yield loss in the second year, Conley said.

"Another thing to pay attention to is nematode resistance characteristics, specifically once we are in more of continuous soybean system," he said. "Right now, over 90 percent of all our soybeans has the same source of resistance for soybean cyst nematode. As we move into a continuous bean system, it is critical to rotate the sources of resistance."

If growers have questions concerning nematodes, they either should contact their local Purdue Extension educator or crop scout to take soil samples and send them for testing to the Purdue Plant and Pest Diagnostic Laboratory to determine what type of nematode is in their field, Conley said. This information helps in variety selection and in rotating sources for nematode resistance.


Writer: Julie Douglas, (765) 496-1050,

Source: Shawn Conley, (765) 494-0895,

Purdue News Service: (765) 494-2096;

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