Record warm temperatures across Manitoba at the end of November and start of December 2015 have producers asking what impact the weather conditions will have on their winter wheat crop.
The quick answer is the warm weather isn’t having a negative impact on winter wheat right now.
Here is why. Over the past several weeks, winter wheat in Manitoba has been undergoing two important physiological changes – cold acclimation and vernalization. It is the cold acclimation process that enables winter wheat plants to ‘harden off’ in order to survive numerous stresses during the over-wintering period.
The optimal conditions for developing the full genetic potential of cold hardiness in winter wheat are:
- Late August or early September seeding into standing stubble, with adequate moisture and temperature conditions to develop plants with 3 to 4 leaves and well-developed crown tissue.
- In Manitoba, majority of these conditions were met this fall, leading to a winter wheat crop that is well-hardened.
- Open field conditions, with little or no snow cover until freeze-up, allowing soil temperatures to gradually decline to freezing levels.
- Once again, Manitoba’s open fall with minimal snow cover to date has allowed our winter wheat crop to become well-hardened.
Winter wheat normally does not reach its maximum cold hardiness potential until after freeze-up in late fall. In Manitoba, full acclimation is usually achieved by late November to early December (see figure below). And although we have seen above normal air temperatures, soil temperatures have ranged between minus 1 to minus 4 degree Celsius over the past few weeks – many degrees away from having plants undergo complete dehardening and breaking of dormancy.
However, one more factor to consider is regardless of the amount of cold acclimation, we typically need to receive good snow cover to protect the crop from the sustained cold temperatures we normally see in January and February in Manitoba.
For more detailed information on winter hardiness in winter wheat, take the time to read the article “Basics of Cold Tolerance and Winter Survival in Winter Wheat’ from the 2001 Manitoba Agronomists Conference at http://www.umanitoba.ca/faculties/afs/MAC_proceedings/2001/pdf/struthers.pdf.
There is also real-time monitoring of soil temperatures in the five winter wheat fields in Manitoba (see the CropChatter post at http://cropchatter.com/monitoring-real-time-soil-temperatures-in-mb-winter-wheat-fields-2/.)
Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD