The ability of the winter wheat plant to survive the winter often depends on its ability to withstand low temperatures. Through the process of “cold acclimation” the plant acquires cold tolerance or winter hardiness. Factors that can impact the level of cold hardiness of the plant include weather, fertility, seeding date, and seeding depth. For the 2014/15 winter wheat crop, majority of acres would likely be considered “well-hardened”.
Measuring Soil Temperature. MAFRD has been measuring soil temperatures in four winter wheat fields throughout the 2014/15 winter (see CropChatter post http://cropchatter.com/monitoring-real-time-soil-temperatures-in-mb-winter-wheat-fields/). Plotting soil temperatures against various ‘hardiness” curves can provide an early indication if there is a concern for winter injury or winterkill.
The figure below illustrates the soil temperatures, measured at a 1″ depth, in four winter wheat fields across Manitoba, plotted against various ‘hardiness’ curves.
Figure 1: 2014/15 Soil Temperatures Measured at 1 Inch Depth in Four Winter Wheat Fields
Since majority of winter wheat acres are considered “well-hardened” and soil temperatures didn’t reach levels that went below the “high hardiness’ curve, winterkill isn’t expected to be a large concern. However, since soil temperatures at one location did dip below the “mid hardiness’ curve, or at some locations got close to that curve, some areas within fields may be impacted.
Early Assessment of Growth. From early reports of producers and agronomists bringing in winter wheat plants from the field or conducting the ‘bag test’ to assess winter survival, regrowth has been noted which is also good news. Continued scouting is encouraged though as fields start to break dormancy and growth resumes with earnest.
So between early assessments and the measured soil temperatures, winter wheat survival looks promising to date. Keep in mind these early indicators shouldn’t stop you from assessing your own winter wheat fields though. As well, the weather in the coming weeks will play a large role in telling the final story of winter wheat’s survival.
Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD