Soybean maturity is determined primarily by daylength, but planting date affects soybean maturity as well. Agronomists estimate that soybean maturity can be delayed by about one day for every four days of planting delay beyond the normal date. Growing conditions such as abnormally cool summer temperatures can also affect soybean growth, development and maturity. When crop maturity is delayed, the risk of damage due to a fall frost increases, especially in northern states where the full growing season is commonly used. This article will discuss managing delayed soybeans and those damaged by a freeze prior to crop maturity.
R6 – Full Seed Stage
R6.5 – Mid-way from Full Seed to Maturity
R7 – Beginning Maturity Stage
R8 – Full Maturity Stage
Figure 1. Soybean growth stages and approximate seed moisture, days to maturity and yield loss from a hard, killing frost that stops seed development.
If soybeans have been frosted prior to maturity or have higher than normal moisture at harvest, combine settings may have to be adjusted to minimize harvest losses. Reduce the concave clearance and then begin to increase rotor or cylinder speed if more aggressive threshing is needed for wet, tough soybeans. Check behind the combine and readjust settings as conditions change throughout the day or season.
Soybeans should be at 16% seed moisture or below for ideal threshing, but with delayed maturity or early frost, some fields may be wetter than this late in the season. In those cases, harvesting at 18% or slightly higher moistures can be attempted if soybeans are sufficiently defoliated, but drying is required. Dryer temperatures need to be significantly lower for soybeans than for corn, as too much heat causes excessive seed coat cracking and eventual splits. Keeping the relative humidity of the drying air above 40% minimizes cracking, but this greatly limits dryer temperature and may not allow the throughput needed.
A normal soybean crop should be dried to 13% for a 6-month storage period, and 12% for 12 months of storage. For lower quality soybeans, experts suggest drying grain one or two points below that required for a normal crop, monitoring grain closely while in storage (at least twice monthly), and storing this grain for only six months rather than a year.
Studies have shown that green soybeans, if properly dried, have the same storage properties as normal soybeans. However, preliminary studies have also shown that green beans do not lose their internal green color, although the surface color may lighten or mottle somewhat after weeks or months in storage. For this reason, growers may want to screen grain prior to storage to remove smaller green beans, to help avoid significant discounts at the elevator.
Berglund, D. 2011. Assessing frost damage in soybeans. North Dakota State University. Online: http://www.ag.ndsu.edu/winterstorm/winter-storm-information-farm-and-ranch-information/farm-and-ranch-crops-soybeans/assessing-frost-damage-in-soybeans
Maier, D. and Parsons, S. 1996. Harvesting, drying, and storing frost-damaged corn and soybeans. Grain Quality Task Force Fact Sheet #27. Purdue University.
The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.