Soybean School: How weather impacts maturity


Cool, wet conditions have Ontario growers wondering when soybeans will mature and whether the crop can escape the impact of fall frosts.

On this episode of the RealAgriculture Soybean School, host Bernard Tobin catches up with Horst Bohner, Ontario Ministry of Agriculture, Food and Rural Affairs soybean specialist, to discuss what needs to happen in the weeks ahead to get combines into soybean fields as quickly as possible for the 2023 harvest.

In this field at Canada’s Outdoor Farm Show (COFS) at Woodstock, Ontario, Bohner says soybean maturity is running 10 to 12 days behind normal. That’s pretty typical of crop development across the province where growers are seeing uneven and slow maturity in their fields.

In the video, Bohner comments on the risk of frost and the potential impacts it could have depending on plant maturity. He also discusses the huge variability he’s seen in the crop, depending on rainfall and disease pressure, and how a longer maturation process could produce bigger seeds and have a positive effect on bean yield.

Soybeans at the COFS site have reached the R6 or green seed stage where the seed has fully developed and fills the capacity of the pod. “Once you hit that we can take some frost and still have pretty normal yield. But that’s not physiological maturity. We don’t reach that until R7 when one of the pods on the main stem turns a mature colour, usually brown.” (Story continues after the video.)

Bohner notes that it typically takes 14 days for the crop to move from R6 to R7. It then takes another 10 days to reach R8 or full maturity. Growers then have to add another five days for drydown before they can realistically run a combine through the field.

For growers doing the math, when the beans start to yellow, harvest is typically four weeks away. But it could be longer depending on the variety and maturity grouping, notes Bohner.  It takes more time for long-season beans to move through the R stages “so that four weeks that I just gave you can be as much as five and a half weeks.”

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