Death comes to us all. Life's but a walking shadow | Did a little research on the effect of cold stress on soybean seed filling. Found a reference to Seddigh & Jolliff, 1984ab in Board & Kahlon 2010 which said this, " Seddigh and Jolliff (1984 a,b) showed that nightly cold temperature of 10 C vs. 16 C or 24 C slowed CGR during the vegetative and early reproductive periods. However, pod and seed numbers were not reduced, because the cooler temperatures extended the period to R5, thus allowing vegetative TDM accumulation to equilibrate across nightly temperature treatments. The 24% yield loss caused by reducing nightly temperature from 16 C to 10 C was entirely due to reduced seed size. "
Translation, reducing night time temperatures from 16 C (60F) to 10 C (50F) didn't have an effect on the number of pods or seeds per pod because the length of time the plants remained in the stage of pod setting was longer. However, those same cool nighttime temperatures later during seed fill caused a 24% yield loss because seed size was reduced.
I couldn't directly access the article but what this tells me is that even without any frost damage the more cool nights the greater the yield reduction. This will be compounded for the later planted beans because it will take longer to form the pods and then reduce the size of the seed.
Essentially seed development gets delayed and then seed fill rate is reduced and the crop runs out of time.
I don't know about the upper Midwest but I'm pretty sure this is happening here with my soybeans.
The bottom line, you don't need to freeze the crop to reduce yield, you just need the cool summer and cooler fall temperatures. |
One more comment on chilling stress during soybean seed filling.
