8-21-09 Dry Beans

8-21-09 Dry Beans

August 21, 2009

Late Planted Beans Likely to Push the First Frost

Western Nebraska’s dry edible bean harvest is likely to drag on weeks longer than in most years, and in areas where planting was late, it will be a race between harvest and first frost.

Nebraska dry bean field
A field of dry beans at the Panhandle Research and Extension Center at Scottsbluff approaches maturity, with some of the bean plants beginning to change color. This field was planted on May 28, earlier than many fields in western Nebraska, and emerged during the first week of June. By mid August it had received more than 1,300 GDDs, and should be ready for harvest in early September. (Photo by David Ostdiek)

Harvest could begin anywhere from early September until late October, depending on when a field of beans emerged, how much stress the bean plants have experienced, and the daily high and low temperatures between now and harvest. In addition, the 2009 crop is likely to experience some quality issues.

This was the assessment offered by UNL Extension Educator Jim Schild of Scottsbluff, who spoke at the 2009 Dry Bean Field Tour on August 18 at the UNL Panhandle Research and Extension Center. The event was co-sponsored by the Nebraska Dry Bean Growers Association.

The 2009 dry bean crop has been challenged by late planting dates in some areas, cool and wet weather across western Nebraska, and localized hail damage.

Dry edible beans reach maturity and are ready to harvest after they have received a certain number of growing-degree days (GDDs). GDDs are calculated by a formula that includes the daily high and low temperatures during the growing season.

So a typical July day with a high of 90 and a low of 60 generates 22.5 growing degree days. But a cool day, with a high of 75 and a low of 50, generates only 12.5 GDDs.

To mature most common great northern bean varieties require anywhere from 1,550 to 1,700 GDDs under non-stress conditions, which translates into growing seasons of 83 days to 90 days. But if young dry bean plants experience stress early in the growing season, as they have in 2009, maturity will be delayed, Schild said.

Stress means they'll need another 150 to 250 GDDs or another 7 to 12 days to the maturity date, pushing back harvest accordingly.

In the North Platte Valley, the number of GDDs that dry beans have experienced in 2009 depends on when they emerged. And there was a wide variation in planting and emergence dates, thanks to cool, wet weather early in the growing season that kept farmers out of the fields for several weeks.

As of mid-August in the Scottsbluff area, beans that emerged on June 1 had received 1,343 GDDs; June 10, 1,251; June 20, 1,120; June 30, 916; and July 10, 725.

The bottom line? Depending on their emergence date, as of mid-August most dry beans in the Scottsbluff area still required 357 to 975 GDDs until maturity. Depending on whether days are warm or cool, it will take anywhere from 18 to 65 days (from mid-August) to accumulate that many GDDs.

So, depending on the weather, Schild projected that likely start-of-harvest dates would vary as follows for each emergence date:

  • June 1 emergence: Sept. 3 to Sept. 9 harvest
  • June 10 emergence: Sept. 7 to Sept. 15 harvest
  • June 20 emergence: Sept. 14 to Sept. 25 harvest
  • June 30 emergence: Sept. 24 to Oct. 6 harvest
  • July 10 emergence: Oct. 3 to Oct. 18 harvest
  • “So it’s safe to say we’ll have a fairly long dry bean harvest in 2009,” Schild said. “When’s the frost going to come? That’s the million-dollar question.”

    David Ostdiek
    Communications Specialist, Panhandle REC