Right now, this year's wheat crop is progressing about normal going into the dormant period, says Robert Klein, University of Nebraska Extension crops specialist. "In some eastern areas of Nebraska, wet weather last fall delayed harvest, so wheat was seeded later than normal. Those few fields will be a bit later in maturing. Many growers increased seeding rates, which should make up for the lower amount of tillering.”
In other wheat production areas, dry weather has plagued farmers, says Drew Lyon, University of Nebraska Extension dryland crops specialist.
In western dryland wheat fields, growers have faced open winter conditions—no snow coverage and windy conditions, Lyon says, and some wheat has burned back.
Klein says that freeze damage most often occurs in fields that are dryer and respond more quickly to spring's warmer days.
"A soil that has a lot of water in it takes longer to warm and cool than dry soil,” Klein says. "We've been fairly wet in eastern Nebraska, so there is no real harm with a few days of warm weather. It's when we are dry that we have real concern about injury from warm days during the winter.”
Check the calendar.
Wheat growers should assess their wheat fields for injury in late February if weather conditions permit and later as one goes farther west and north. Even then, it will take a week or more of warm temperatures before active wheat growth begins and you can assess the condition of your winter wheat crop. Lyon suggests that producers wait until wheat starts to green up before making crop decisions, if possible.
In Nebraska, typical spring tillering will occur from March through mid-April. At this time, the growing points are located just below the soil surface, which will protect them from injury.
While some main tillers may be killed or injured in a hard freeze, others may survive and help compensate for some lost yield. At this stage, injury may reduce tiller numbers, but growth of new leaves and tillers usually resumes with warm temperatures.
The jointing stage is when the stem segments between joints or nodes are elongating the wheat stem and the embryonic head is moving up the stems. This usually occurs from early April through early May, Klein says. Injury at this time is critical—stem growth will stop immediately when growing points are injured.
Signs to watch.
There are a number of environmental factors that determine how much freeze injury you should expect. They include: air temperature, soil moisture, stand, canopy density and winter wheat growth stage. Others include the length of time of the low temperature, wind speed and temperature gradient in the field. It is unlikely that all parts of the field will have the same amount of damage.
Take time to thoroughly evaluate wheat fields before making a cropping decision, Klein reminds growers. "First, contact your crop insurance agent
before you go in a field with the intention of planting another crop.”
However, even watching the calendar and scouting provide growers limited alternatives. "Mother Nature is always in charge,” Klein says. "We don't ever want to forget that.”
"The saying goes that wheat dies seven deaths, so we haven't killed it yet,” Lyon says.
You can e-mail Sara Brown at firstname.lastname@example.org
- February 2009