The winter weather in Kansas so far has been unusually warm and wet, for the most part (see article below). This has caused wheat to green up, and has created some concern about whether this will make the wheat more susceptible to cold injury if temperatures were to drop sharply.
Although the wheat is green, and may even be growing a bit in the more southern areas of Kansas, that does not mean it has lost all of its winterhardiness. As long as nighttime temperatures are below freezing for the most part, wheat will retain its winterhardiness – although not quite the level of winterhardiness it would have in a “normal” winter.
An occasional period of 1 to 3 days where nighttime temperatures do not get below freezing will not cause any significant loss of winterhardiness either. But if nighttime temperatures consistently stay above freezing for a week or so, there will be some loss of winterhardiness.
The process of gaining and losing winterhardiness in winter wheat is a gradual one. Temperatures fluctuate most years as winter begins and ends, and the winterhardiness level of wheat tends to ratchet up and down with the temperatures. After a warm spell in winter, wheat will lose some winterhardiness – but wheat will regain its winterhardiness as temperatures get cold again. Every time this happens, however, the wheat will lose some winterhardiness. The peak level of winterhardiness in wheat occurs when temperatures get cold and stay cold all winter. Wheat that greens up and then goes back into dormancy will not have quite the same level of winterhardiness as wheat that remains dormant all winter.
So the bottom line is that wheat in Kansas should still have an acceptable level of winterhardiness at this point. Nighttime temperatures have been cold enough to that wheat to retain its winterhardiness.
The bigger concern for wheat in general is the problem of dry subsoils. Topsoil moisture is generally good to adequate in most of Kansas right now, and this has producers optimistic about the prospects for this year’s wheat crop. But subsoils began the fall in very dry conditions, and this has not yet changed. In the August 26, 2011 issue of the Agronomy e-Update (No. 314), an article explained that about 12 inches of rain would typically be needed to truly replenish soil moisture in the driest areas of the state. A look at the chart in the article below shows that we are far from having this kind of moisture yet.
There is definitely more reason for optimism about this year’s wheat crop than there was at planting time. Topsoil moisture has improved and southern areas of Kansas even have enough growth for some livestock grazing. But the dry subsoils could be a problem later this spring if we don’t get more rainfall. Also, if nighttime temperatures in January and February are consistently above freezing for several days in a row, the wheat could lose much of its winterhardiness and be susceptible to cold injury from a sudden drop in temperatures. At the moment, this is not a concern, however.