Shatter-Prone Soybeans

ST. LOUIS (DTN) -- Pete Bardole's soybean fields are talking to him, and the central Iowa farmer doesn't like what he's hearing.

"You can just stand there and listen, and you can hear the beans popping across the field," he said. "And that's never a good sound."

Bardole's no-till corn and soybean operation near Jefferson, Iowa, has seen about 15 inches of rain since the first of September, he told DTN. After the latest 1.5- to 2-inch rainfall last week, his soybeans began to voice their displeasure.

"They've just been wet and dry so much, the pods are opening up," he explained.

The risk for in-pod germination will also rise with each fall rainfall, but that phenomenon is very rare, Extension agronomists and educators told DTN. More critically, farmers should begin to adjust harvest schedules and strategies in the face of increasingly fragile beans.

PRIORITIZE SHATTER-PRONE FIELDS

As soybeans swell up after rainfalls or damp nights and then dry down repeatedly, the beans and pods can become more fragile, Iowa State Extension agronomist Mark Johnson explained.

In some cases, movements as mild as a breeze can cause the pods to split open, hence Bardole's unprovoked, in-field symphony of pops, University of Illinois Extension educator Dennis Bowman explained.

The wetting and drying cycle can also result in more split and broken beans, Bowman added. For farmers like Bardole, who grow soybeans for seed companies, this might mean a loss of premiums.

As a result, Bardole is making the fields where his beans are audibly shattering a top harvesting priority. "Those fields were still wet, but when I heard them popping, we decided we had to get in to get what we can," he explained. "If we have to come in later and combine wet spots that we had to dodge, we'll do that."

The problem will only get worse as the weeks proceed, Bowman confirmed. "This is kind of a natural characteristic of soybeans to survive when they get to a certain dryness point -- the pods shatter to spread their seeds so they can reproduce."

That dryness point tends to be around 10% moisture content, he said. Farmers can try to harvest overly dry, fragile bean fields when the air is less dry, Johnson said. Early mornings after dew falls or in the evening when the air is cooling down are best. "Avoid the middle part of the day, when the air is driest," he said. "Beans' moisture will fluctuate with the air moisture."

Perfect timing can be tricky for farmers in areas that have seen a lot of rain, Bowman conceded. Farmers will have to balance the need for dry, stable fields with the need to get soybeans out with minimal shatter loss, he said.

That window is getting even tighter given green-stem characteristics of many popular high-yielding soybean varieties, said Kevin Bien, AGCO brand marketing manager for Gleaner combines. Bien spoke to DTN from the combine cab in between seed-loss trials using various combine and header types and machine settings in Illinois.

"We're seeing the pods are dry, the seeds are ready to be harvested, but the base of the stems of these varieties are still a little green." Cool, moist evening air, good for lessening pod brittleness, also makes stems tougher.

"That means your sickle has to be as sharp as possible to cut the stem, rather than tearing it, which shakes the plant and shatters out beans," Bien said. Sharp sickle sections and unworn sickle guards are always important, Bien said, but they are extremely critical in the conditions many soybean fields are in this week.

The DTN/Progressive Farmer weather forecast calls for the Great Lakes area to have the highest risk of wet-weather concerns through the end of October. Michigan's bean acreage was only 23% harvested on Oct. 20, according to USDA reports.

Bowman said growers will need to experiment with combine settings when harvesting a shatter-prone field. Typically, slower ground speeds and faster real speeds are the answer, but they must be calibrated carefully through trial and error.

Bien added that growers with access to the newer draper-style combine heads can gain an advantage by using the hydraulic header pitch control to "roll back" the header slightly, which keeps from "bulldozing" or pushing bean plants away from the header. Harvesting fields on the diagonal, versus parallel to the row, also can reduce shattering, but also requires a super-sharp sickle bar.

VET YOUR VARIETIES

Shatter rates in soybeans will vary from variety to variety, and this year could be a good one to evaluate which soybeans were more shatter-prone, Bowman said.

Most years, farmers can anticipate an average rate of shatter loss around 5%, according to a University of Missouri Extension guide.

"These are the heaviest, thickest, gnarliest soybeans we've seen in decades of equipment testing," Bien said of the conditions he was running through in north-central Illinois. "You really have to have everything just right," not to see shatter loss. It is possible, he stressed. In the Gleaner tests, with speeds and header conditions optimal, he reported cutting 84-bushel-per-acre soybeans with only one-half bushel per acre loss.

In a year like this one, Bardole suspects the shatter loss percentage for some of his fields will get into the teens and make a dent in overall yields. "We got rained out one night, when we partway done with a field," he recalled. "When we went back four to five days later, there was a noticeable drop in yield from before the rain to after."

The Missouri guide establishes a chart for scouting fields for shatter and other types of harvest loss. You can find the guide, which also outlines how to best avoid shatter during harvest, here: http://goo.gl/….

In addition to evaluating the shatter rates in their varieties, farmers may also benefit from "spreading their risk" of shatter by selecting a range of maturities for planting next year, Bowman added.

"A lot of people look at what's going to give the maximum yield and end up with most of their acres in one, two, or three different varieties, all with very similar maturities," he pointed out. "This fall, something they may want to think about is varying their maturities more so they're not all coming into maturity at the same time."

In the meantime, all you can do is check your fields for weakened pods and harvest them as quickly as possible, Bardole concluded.

"The later we get with harvest, the more trouble we're going to have," he said.

Emily Unglesbee can be reached at emily.unglesbee@dtn.com

Follow Emily Unglesbee on Twitter @Emily_Unglesbee.

Editors note: This story was reposted with additional information.

(GH/AG)

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