Plant growth regulators (PGRs) are an excellent tool for controlling the height of a wheat crop, and they also impact stem strength, especially for a crop under high management.

“Lodging is caused by high nitrogen rates, or excessive nitrogen, and also high seeding rates,” says Mike Holzworth, research agronomist with C&M Seeds.

In this Wheat School episode, resident RealAg agronomist Peter “Wheat Pete” Johnson has a chat with Holzworth, about some trials that C&M Seeds has conducted this year, looking at PGR use in their winter wheat varieties.

The trials include the use of two different PGRs, three different varieties, three different seeding rates, and four different nitrogen rates, the highest of which being 220 lbs/ac.

Johnson notes that crops aren’t always shortened by a well-timed PGR application, but in the high seeding rate and high nitrogen rate plot, treated with PGR, the difference between the treated plot and the untreated plot is noticeable.

In the video, Holzworth and Johnson point out the resistance to wind that the treated plot has, story continues below. 

C&M Seeds also played around with the timing of PGR application for the trials, noting that the shortening effect is still there, but the impact to the plant is higher up.

“We applied it a little later, we had about eight days of cool weather, and I just wanted to be a little bit safe. It was applied at growth stage 39, so a little bit later than the recommended time,” says Holzworth. “The later you apply it the higher up it’s going to shrink.”

Applying a PGR later in the game still works, but isn’t quite at the desired spot in the plant — the upper internodes of the plant are shortened, instead of the lower internodes, which happens when the PGR is applied at growth stage 30 to 31.

Holzworth has also seen negative effects of PGRs on certain winter wheat varieties, so it’s a good idea to talk with your seed provider about which varieties excel with a PGR application.

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