Soybean Pod Shattering

Monday, October 27, 2014

As of the Oct. 19 USDA report, only 51 percent of the corn and 24 percent of the soybean crop has been harvested in Missouri. The soybean crop could be in the field for a while longer depending on weather, harvest progress and storage availability.

The longer the soybean crop is in the field the more the likelihood of shattering occurring. As soybeans swell up after rainfalls or nights with heavy dews and then dry down repeatedly, the beans and pods will become more fragile. In some cases, movements as mild as a breeze can cause the pods to split open. The wetting and drying cycles can also result in more split and broken soybeans.

The problem will only get worse as the weeks progress. This is a kind of a natural characteristic of soybeans to survive when they get to a certain moisture content. At this moisture content the pods shatter to spread their seeds so they can reproduce. That dryness point tends to be around 10 percent moisture content. If harvesting overly dry, fragile soybeans, try harvesting when the air is less dry such as early mornings after the dew falls or in the evening when the air is cooling down. Avoid the middle part of the day when the air is the driest. Perfect timing can be tricky. Producers will have to balance the need for dry stable fields with the need to get the soybeans out with minimal shatter loss.

The green stem characteristic associated with many popular high-yielding soybean varieties will make the window for harvesting even tighter. Even when the pods are dry and the seeds are ready for harvest, 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. Sharp sickle sections and unworn sickle guards are always important but especially with green stems to prevent tearing of the stem which will shake the plant and shatter out beans. Combines with a draper head can gain an advantage by using the hydraulic header pitch control to "roll back" the header slightly to keep from bulldozing or pushing soybean plants away from the header.

Another potential concern of soybean harvest is delayed germination of the seed in the pod. Soybeans produce hormones (abscisic acid) that prevent germination. As seeds approach maximum dry weight and seed moisture decreases, the hormone balance changes from concentrations that prevent germination to concentrations that allow germination. Soybeans can germinate when temperatures are above 50 degrees fahrenheit and seed moisture percentages are above 50 percent. Weather conditions this fall are conducive to premature sprouting of soybean seeds.

Watch fields for shattering problems or premature germination and plan harvest accordingly.