How did the cold temperatures affect my winter wheat?

Extremely cold temperatures were experienced throughout Manitoba at the end of December and beginning of January. The cold temperatures combined with limited amounts of snow cover have many winter wheat producers thinking about winter survival.

Manitoba Agriculture’s Ag Weather Program has been monitoring soil temperatures in winter wheat fields for a number of years. There are currently three weather stations measuring real time soil temperatures in winter wheat fields at Alexander, Dauphin, and Kleefeld.  The data collected from the weather stations is made available to the University of Saskatchewan and Western Ag Labs for their Winter Cereal Survival Model, available at:  The Winter Cereal Survival Model compares the cold tolerance of winter wheat varieties to the daily average soil temperature at crown depth (about 1”).

Plotting the soil temperatures against hardiness curves can give an early indication if there is a concern for winter injury or winterkill. Factors that can impact the level of cold hardiness of the plant include weather, fertility, seeding date, and seeding depth.  In Manitoba, the majority of winter wheat acres would likely be considered to be well-hardened.  The figure below shows soil temperatures at 1” depth in three winter wheat fields in Manitoba, plotted against three hardiness curves.

Figure 1. 2017/18 soil temperatures (as of January 16, 2018) measured at 1” depth in three winter wheat fields. Data Source: Manitoba Agriculture Ag Weather Program

Soil temperatures in Alexander and Dauphin dipped below the low hardiness curve, but have not approached the mid and high-hardiness curves at this point. To assess the level of risk on your farm consider how well-hardened your field may be and check your fields for level of snow accumulation.  It is still early in the season, so check back in on the Winter Wheat Survival Model throughout the winter to get an idea of the risk of winterkill in your area.

Submitted by: Anne Kirk, Provincial Cereal Crops Specialist, Manitoba Agriculture


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Considerations for Overwintering Corn

The vast majority of corn in Manitoba is in the bin, but what about those few fields that may not be harvested yet? In some cases weather conditions may have made it difficult for farmers to harvest corn in the fall, but some farmers may decide that the corn moisture level and costs associated with drying mean that it is more economical to leave corn in the field to let it dry down naturally over winter.

Just how much dry down can be expected over winter? The amount of drying that occurs in the field depends on the corn maturity, variety, and moisture content, as well as environmental factors such as temperature, humidity, solar radiation, and wind speed. Field drying is extremely slow in the winter, and corn will only dry to about 20 to 21% moisture content. In a typical year, it is expected that corn will dry approximately 11-12% in October, 4-5% in November, and just 2% per month in December and January (Table 1).      

Table 1. Estimated corn field drying


EMC (%)* GDD PET (in.) Estimated Drying (% pt.)
Month Week
Sept 15 250-350 4-5 18 4.5
Oct 16 100-125 2.8-3.5 11-12 2.5
Nov 19 20-30 0.8-1.2 4-5 1
Dec 20 0 0.5-0.8 2 0.5
Jan 21 0 0.5-0.8 2 0.5
Feb 21 0 0.5-0.9 3 0.8
Mar 19 0 1.3-1.6 5 1
Apr 16 50-90 3.2-4.5 16 4
May 14 200-300 6.5-8.5 30 7

*EMC – equilibrium moisture content, GDD – growing degree days, PET – potential evapotranspiration 1EMC is the moisture content to which corn will dry and is based on air temperature and relative humidity

Source: Ken Hellevang, 2009. 2009 Post-harvest tips for later maturing corn. NDSU Extension Service.

Risks of overwintering corn Heavy snowfall during the winter can cause significant amounts of lodging resulting in yield losses. Root and stalk strength should be taken into consideration when deciding if a field should be overwintered. Research conducted at the University of Wisconsin examined corn yield loss during the winter (Table 2).

This researched showed that in 2000, a year with heavy snow cover, yield loss was much greater than in 2001, a year with very little snow cover.  Standing corn may result in more snow catch and slow soil drying in the spring, which could delay planting.

Table 2. Percent yield loss of corn left standing in the field through winter at Arlington, Wisconsin.

Harvest Month
Year Nov Dec Jan Feb Mar Apr
2000 No Loss 45% 58% 59% 65% 38%
2001 5% 5% 9% 18% 7% 10%
Mean 3% 22% 32% 37% 32% 24%

Source: Schneider and Lauer, 2009. Weight risk of leaving corn stand through winter. UW Extension -Team Grains.

Corn can be harvested throughout the winter if conditions are cool and there isn’t much snow. If stalks stay standing throughout the winter, and ear drop and wildlife damage are limited, corn can get through the winter without much yield loss.  Yield loss throughout the winter will vary by hybrid and environmental conditions.

If you are planning to over winter corn please contact your local MASC agent.

Submitted by Anne Kirk, Cereals Specialist, Manitoba Agriculture


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