Soybean harvest is well underway, and farmers are pushing to get soybeans out of fields in order to get their next crops in the ground.

That push could depend a lot on variety maturity dates and planting dates and in this Soybean School episode, Bernard Tobin joins Horst Bohner, OMAFRA soybean specialist, to discuss how the two agronomic concepts impact harvest date.

“A number of years ago, we shifted from using crop heat units to maturity groups for soybean,” says Bohner. “The basic difference is that crop heat units only really use temperature to define how much growth a plant can have.”

With maturity grouping systems in soybeans, photo-period, or how long the days are, and sensitivity is taken into account because soybeans can adjust to the season based on day length, says Bohner.

The difference between a group one soybean and a group two, is about six to ten days, and each decimal point difference in the rating system, is about one day maturity difference in the fall.

In the video below, Bohner points out differences between maturity in a 0.9, a 1.2, and a 1.8 group soybean, all planted on the same day, April 26:

Getting the soybeans off, in a good, timely fashion, in order to get the next crop in, means considering planting a maturity that is shorter in length than what’s adapted for the area — by 0.5 or even one full maturity group earlier, says Bohner.

Ok, so that covers maturity groups, but why is planting date so important?

“Planting date is extremely important. These April 26th planted beans will finish much earlier than our typical May 18th planting date. So, there’s a three week difference in planting date, and we would expect only a one week difference in terms of finally finishing those beans,” says Bohner.

In trials that have been done on a variety that’s adapted to a zone, if it’s more than a zero, planted a month later, it will finish up to 15 days faster in terms of the R1 to R6 stages. Bohner adds that a very short season soybean, like a zero or 00, they’re basically like corn and aren’t photosensitive at all  because they finish up so quickly.

“Take home message is that variety selection is extremely important, but planting date is equally important, in terms of trying to get those beans to finish in a good time in the fall,” says Bohner.

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