How Do Seasonal Weather Fluctuations Impact Soybean Seed Size, Protein, and Oil Composition?

Farmers often describe growing seasons based on the weather conditions experienced. For example, one year may be a "dry year" followed by a "hot and wet year" the next. Weather patterns have an impact on how a farmer manages their fields and influence their variety choices, chemical decisions, tillage, and more. Various weather conditions impact how the soybean plant grows and the composition of the individual bean.

SEED SIZE

Soybeans have a range of seed sizes from 8 grams/100 seeds(nattos) to 35 grams/100 seeds. The size of a soybean is predominately determined by the variety's genetic makeup but seasonal weather influences can also have an effect.

PROTEIN AND OIL COMPOSITION

Similar to seed size, a variety's oil and protein percentage are largely determined by the product's genetics. Varieties with high protein tend to have lower oil content. The opposite is true for high oil varieties which tend to have lower protein percentages. Typically, Canadian food-grade soybeans are higher in protein and intermediate in oil levels. A variety may fluctuate 2-3% in protein content depending on the growing season.

Due to the inverse relationship between oil and protein, years that score high in one tend to score low in the other. For example, in growing seasons with elevated protein, oil may be below average.

Let's take a more in-depth look at how different conditions impact the soybean seed. Click on the chart to view it larger. 

Additional weather conditions that may impact soybean seed size and composition: 

• If dry conditions during flowering are alleviated during seed fill, the soybean plant may attempt to add yield by making larger seeds. This may result in lower protein levels.
• Above-average sunshine hours can reduce protein and elevate oil content.
• Larger fluctuations in daytime and nighttime temperatures can reduce protein and elevate oil content.
• Soybean injury (from extreme weather events or insect feeding) can reduce protein. 

Soybean protein and oil composition can also be impacted by nutrient deficiencies. This is why it is important for farmers to monitor their soil fertility and use recommended production practices. Here is how different nutrient deficiencies can impact the seed composition:

Varieties are unique and respond to stress differently. Different soil types can respond quite differently to similar levels of precipitation. The impact is dependent on the severity of the conditions. For example, extreme drought will have significant impact.

Many factors impact soybean seed size and protein and oil compositions. It can be very difficult to predict how soybeans will perform each year and what the seed size and composition will be. Farmers can help their soybeans succeed by selecting the right variety for their growing situation, managing their soil fertility, controlling weeks, and harvesting under good conditions. 

To see the protein, oil, and seed size of our varieties, visit our website. Note this article was written for Sevita's export customers. Any questions can be directed to a Sevita Representative.