Soybean Pod Splitting and Seed Sprouting

• Prolonged wet conditions late in the season can cause substantial delays in harvest and lead to yield losses due to pod splitting and seed germination in the pods.
• Two conditions are necessary for soybeans to germinate in the pods following physiological maturity:
  • Seed moisture raised back above 50%
  • Temperatures greater than 50ºF

• Soybean seed moisture is around 35% at physiological maturity and will decline quickly under dry conditions, drying down much more rapidly than corn.
• However, soybeans will readily re-absorb water and expand when exposed to moisture.
• Frequent rains and persistent wet conditions can allow water to soak through the pods and cause the seeds to swell inside the pods.
• If the seeds swell enough, they can cause the pod to rupture (Figure 1).
• Soybeans that experienced drought stress earlier in the season can have an elevated risk due to smaller and weaker pods.
• When pods are ruptured, seeds are prone to loss, particularly when they dry back down, either before or during harvest (Figure 2).

• Once the pod has ruptured, the seeds are directly exposed to soaking rainfall. If the seeds swell to above 50% moisture and temperatures are above 50ºF, they may begin to germinate (Figure 3).
• Germination will continue as long as moisture and temperatures remain favorable.

• Affected fields should be harvested as soon as feasible to prevent further loss of yield and quality.
• If soybean plants have retained green foliage due to wet conditions, a desiccant may be needed.

Combine Speed and Settings

• Slowing down harvest speed can help reduce gathering losses. Keep forward speed at about 3 mph for most combines. Slow down for uneven soil surface or other abnormal conditions.
• Equipment must be properly adjusted and carefully operated to minimize losses. Soybeans that never get inside the combine can account for 80 to 85% of harvest losses.
  • Be sure knife sections and ledger plates are sharp, and that wear plates, hold-down clips, and guards are properly adjusted. Chains and bearings should be properly lubricated, and belts tight.
  • Proper reel speed in relation to ground speed will reduce gathering losses. Shatter increases if the reel turns too fast; stalks may be dropped if the reel turns too slow. Use a reel speed about 25% faster than ground speed.
  • The reel axle should be 6 to 12 inches ahead of the sickle in most cases. Operate a bat reel just low enough to tip cut stalks onto the platform. The tips of the fingers on a pickup reel should clear the cutterbar by about 2 inches.