Soybean conditions before harvest - Pod shattering
Soybean harvest is moving slow across the state (less than 20% completed, according to the USDA Kansas Agricultural Statistics). Soybean grain-filling conditions were close to optimal in many areas but precipitation and wet weather conditions during the last week can produce harvest delays.
In addition to the delay on harvesting time, a potential for soybean pod shattering can occur before harvest when dry pods are rehydrated under wet conditions and mild temperatures. Alternation of dry and wet periods cause swelling and shrinking that can break the pod (Figure 1). If moisture is reaching the seeds, then there is a high probability of those seeds to sprout. In the case of pod shattering, those seeds that they are fall to the ground represent a yield loss before harvest. A loss of four seeds per square foot on the soil surface represents around one bushel per acre yield loss (Figure 2).
Figure 1. Soybeans in eastern Kansas exhibiting pod shattering due to excessive moisture and mild temperatures. Photo submitted and used by permission.
Figure 2. Example of four soybean seeds on the soil surface in one square foot. This correlates to around 1 bushel per acre of yield loss. Photo provided by Bill Schapaugh, K-State Research and Extension.
Whenever conditions allow a return to harvest, it would be best to harvest fields presenting potential issues on shattering sooner to reduce this problem and the potential loss in seed quality. Early sprouting reduces overall seed quality.
There are several factors that influence pod shattering including: fertility (lack of it), insect or hail damage to the plants, and weather conditions (the major factor this harvest season). As a management consideration, early harvest and combine adjustments may help reduce potential yield losses on soybeans.
Harvesting beans before the leaves have dropped can be messy and gum up the combine, but at least the yield level will be maintained. Make sure harvesting equipment is sharp and in top condition. Taking it slow in the field can also reduce shatter losses.
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
Stu Duncan, Northeast Area Crops and Soils Specialist
Bill Schapaugh, Soybean Breeder