Soybean School: Early flowering has pros and cons

It has long been believed that soybean doesn’t flower until after the summer solstice — June 21, the longest day of the year. Research from Dr. Shawn Conley and his team from the University of Wisconsin-Madison says otherwise, and in this episode of Soybean School, Conley joins Bernard Tobin to chat about early flowering in soybeans.

Soybeans are a ‘short-day’ plant, but this name is misleading because soybeans actually measure the length of the night, not the day. So, soybean flowering is induced when the night is longest.

“By planting our soybeans earlier, we’re actually triggering flowering  induction as the days start getting longer,” says Conley. “So we’re actually triggering it on the front end, where typically when we used to plant soybeans, we were triggering it on the back end.”

Modern genetics in soybeans mean specific adaptation to latitudinal zones and allow for less vegetative growing time by about a week, and about an extra two weeks at the reproductive stage. Adding management practices into that, the grain-fill period has been extended.

The downside of earlier flowering means quicker vegetative growth and that quick canopy closure can mean white mould, something to be conscious of, says Conley. “We can’t spray by calendar,” says Conley. “If we’re planting earlier we need to make sure we’re out there scouting.” That R1 timing is crucial for fungicide timing.

Stressful environmental conditions — drought in particular — could mean flower or pod abortion; however, since soybeans can flower for up to six weeks, it means the plant can still produce more flowers. Those dry conditions might also help out with the fungicide bill.

Watch the full interview between Conley and Tobin below: 

Check out this great article from Conley and his research team on the Soybean Flowering Fallacy.

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