With temperatures dipping below zero in various parts of the province last night and continued cold temperatures forecasted into the weekend, many are wondering what effect this will have on cereal crops.
What temperatures will cause injury?
It shows the various wheat growth stages and when injury is likely to occur to the crop after experiencing cold temperatures for a two hour duration. Other crops such as triticale and rye are slightly more cold tolerant while spring cereals such as oats and barley are more sensitive. However, they are less sensitive to cold injury currently based on their growth stage relative to planting date.
The amount of injury that occurs is highly dependent on the growth stage of the crop and the amount of time the crop is exposed to the cold temperatures. The later the growth stage, the greater risk of injury at low temperatures. Soil mositure can also have an impact with dry soils being more prone to temperature fluctuations because they give off built up heat quicker.
Most of the winter wheat crop in the province is at growth stage(GS) 33 (3rd node) or less while most spring cereals are not yet at the tillering stage. Fields that are up to GS29 (tillering), can withstand temperatures as low as -11°C (table 1). Once temperatures fall to -11°C injury can be identified by leaf tip burning and chlorosis as well as a silage odour. Temperatures are not expected to get that low so the risk of injury is relatively low. However, those fields currently at stem elongation or the jointing stage (GS30), are less tolerant to cold temperatures. Once at the jointing stage cereals are susceptible to injury if temperatures fall to -4°C for two hours or more. At this point death of the growing point can occur with splitting or bending of the lower stem and leaf yellowing or burning. Yield losses with cold temperatures at this stage can be anywhere from moderate to severe.
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