Specialist: Soybeans more mature for their age than some think

Many producers are convinced their soybean fields are way behind in development but that's not necessarily the case, said Shawn Conley, Purdue University Extension soybean specialist.

"We're hearing a lot of talk around the state about how far behind our soybean crop is in its maturity," Conley said. "Actually, the crop is about where it needs to be for this time of year.

"Producers think their soybeans are behind because they are comparing this season to last year. In 2005, about 25 percent of all Indiana growers started planting soybeans before May 1, so a lot of beans went in early and, as a result, harvest dates were pushed up."

Although Indiana's soybean crop trails the five-year development average, the crop is in better overall shape than it was one year ago, according to the Indiana Agricultural Statistics Service (IASS).

For the week ending Sunday (9/3), the state's soybean crop was rated 73 percent good to excellent, compared to 52 percent one year earlier, the IASS reported. Six percent of crop was shedding leaves by Sunday, compared to 13 percent in 2005 and 16 percent for the five-year average.

Indiana farmers are projected to produce 278.3 million bushels of soybeans this fall, at an average yield of 49 bushels per acre.

Spring storms slowed soybean planting in many areas of the state, contributing to the crop's later development. Some growers who planted early had to start over, Conley said.

"Weather conditions caused delayed emergence or, in many cases, replanting in many early planted fields," he said. "If you look at how a soybean plant grows and develops, a one-month delay at the beginning of the season equates to about a two-week delay in maturity at the end of the season."

Producers should not be fooled by a soybean crop that appears weeks away from harvest, Conley said.

"Once a soybean plant reaches the R7 growth stage, it is physiologically mature," he said. "The R7 growth stage is when one pod per plant is starting to turn a tan color. If a crop is in the R7 stage and cool weather or frost occurs, there should not be any yield loss."

Yield potential can be reduced, however, if a farmer leaves the crop in the field and weather turns unfavorable, Conley said.

"The only yield loss we might see is if growers don't harvest their soybeans in a timely manner and the crop goes through additional wet-dry cycles," he said. "If soybeans dry down and then become wet from additional rainfall, they will absorb some moisture and then start to dry down again. When that happens there's the threat of shattering, which means the pods themselves split and are ruined, and test weights tend to drop.

"Corn generally has better standability in the fall, so if growers have to choose between harvesting corn or soybeans first, they should begin with the soybeans."

Other late-season soybean issues producers could face include:

• Fungicide-related development — "If a grower applied a fungicide in 2006 those fields will have a delayed maturity," Conley said. "Depending on the variety a grower might see what is known as 'green stem syndrome,' where the stem is green but the pods are ripe."

• Sudden Death Syndrome (SDS) — The devastating fungal disease is showing up in some fields, Conley said. Growers cannot control SDS but should make note of fields where the disease is present, so that they can plant a SDS-tolerant variety in future years.

• Hail damage — "If a soybean crop was damaged by hail early in the season, that crop can recover," Conley said. "If hail damage occurs late in the season, growers should check their fields to see what kind of pod damage they've got and if there were any germinating seeds in those pods. Late-season damage can affect yield and crop quality during harvest."

For additional information about soybean management, visit Conley's Cool Bean Web site.

Writer: Steve Leer, (765) 494-8415, sleer@purdue.edu

Source: Shawn Conley, (765) 494-0895, conleysp@purdue.edu

Ag Communications: (765) 494-2722;
Beth Forbes, forbes@purdue.edu
Agriculture News Page

Related Web site:
Purdue University Department of Agronomy

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