Over the past decade, growers have pushed soybean planting dates earlier as they pursue higher yields.
Earlier planting extends the growing season, but rolling out the planter in late April also impacts several other factors that contribute to yield, says Horst Bohner, soybean specialist for the Ontario Ministry of Agriculture, Food and Rural Affairs.
Planting early also leads to more nodes on the plant before flowering, which can have a significant impact on yield, notes Bohner. He likes to see six trifoliates on a plant at flowering. When growers plant late there may only be three trifoliates at this stage.
Planting date also impacts the plant’s ability to take advantage of longer summer days and optimum growing conditions. “July delivers much more solar radiation than can be captured in August,” adds Bohner. “When you plant later you’ve missed out on some of the best solar radiation that the season has to offer.”
How early should growers plant soybeans to take advantage of these yield-enhancing factors? Bohner notes that the oilseed has a reputation for not liking cold soil, but that perception continues to fade as research and field performance provides more evidence that soybeans are really quite tough.
On this episode of RealAgriculture’s Soybean School, Bohner shares results from a planting date trial he conducted in 2020 with no-till soybeans planted in 15-inch rows at 175,000 seeds/ac. In the trial, soybeans were planted on five dates ranging from April 22 to June 10. (Story continues after the video)
Bohner notes that the seed planted on the earliest date (April 22) had to endure cold temperatures that dipped to -4 °C within 12 hours of planting. Despite the shivering cold, these soybeans produced an acceptable plant stand (134,000 plants/ac) and the second-highest yield in the trial at 64.1 bu/ac.
“At the end of the day, soil temperature is not that important for soybeans,” Bohner concludes. But, if conditions are wet and cold or whether a cold rain is expected immediately after planting, parking the planter would be a prudent course of action.
Overall, Bohner believes growers should not be afraid of planting a portion of their acres in the latter part of April in Ontario — if the weather looks good and the ground is fit.
Click here for more Soybean School episodes.