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Posted 29 June 2015. PMN Crop News.

Growing Pains

Soybeans’ growth stage at time of stress can make a big impact on yield

Source: United Soybean Board Press Release.

Chesterfield, Missouri (June 2, 2015)--Sometimes, the day a crop is stressed makes all the difference.


The effects that fertilization, frost, hail, moisture stress, diseases and pesticide applications have on yield will be determined by the growth stage of the plant at the time these events occur. Proper identification of that growth stage is important.

“Understanding growth and development is key to fine-tuning your crop system,” says agronomist Ken Ferrie. “Knowing the effects of stress based on growth stage of a plant is important in optimizing yield.”

Three factors impact yield: number of pods, number of beans per pod and weight per bean (seed size). Because of these three components, stress on a crop can change yield in different ways at different times.

Yield results from stress based on growth stage.

The largest yield impacts result from changing the number of pods per plant, so if a plant is stressed during the R1-R4 stages, its yield will be affected more than if the plant is stressed during the R5 or R6 stages.

Most environmental stress events, such as heat, frost or hail, are out of a farmer’s control. One way to mitigate the weather is to diversify risk by planting beans at different times so they are at different maturities if stress does occur.

Knowledge of growth stages can come in handy when considering the right time to apply fertilizer or pesticides.

“I know many farmers who say they will spray when their soybeans get to a certain height,” Ferrie says. “But you can’t spray off the height of the plant. To optimize yield, you need to look at its reproductive stage.”