How To Read the Graph
- The Blue Line: The Daily Average Soil Temperature at Crown (~3 cm depth).
- The Black Line: Plant Winter Hardiness Lethal Temperature where up to 50% plant kill could occur.
- The Red Dots: Indicate that a Winter Kill or a crop damaging event has occurred.
- Winter Kill Index: Is an indication of the cumulative damage sustained to the crop through the winter. The index ranges from 0 to 50. The higher the index value, the greater the crop damage. Index values 13 and below indicate minimal crop damage. Values 14-22 indicate moderate damage is likely. Close inspection of the crop is necessary to determine if adequate stand density was maintained. Index ratings above 22 generally mean severe damage has occurred to the crop and it is likely that the crop will need to be terminated. You will notice that the background of the graph will change at these different levels as a visual cue to the damage that may have occurred. In all cases, the crop stand should be inspected in the spring, once it has had an opportunity to re-grow. Winter cereals have a tremendous ability to tiller and "fill in". The Winter Cereal Survival Model serves as a guideline only.
- *Note* On the top right corner of the graph, the user can print or save the graph image
Using the Model: Basic Usage
Narrow down the number of displayed locations using the Location Filter boxes.
The filters are applied in an AND manner, meaning that only locations that meet
all the selected filter requirements are displayed on the map.
Select a location by clicking a marker on the map or the site description in the list box above the map.
Select a cultivar of interest.
Modify Graph Preferences
More on Winter Hardiness:
Winter cereals go through several phases that facilitate winter survival. These phases are shown on the "Winter Hardiness" graph in the red, LT50, line. The first phase, during the period of September into October, represents the growth phase of the crop's crown tissue. Ideally, the winter cereal growing three full leaves usually indicates sufficient crown tissue development to optimize survival.
The second phase, shown with the LT50 line declining, represents the winter cereal going through cold temperature acclimation. Low-temperature acclimation, the maintenance of low-temperature tolerance, and the degree of low-temperature injury during the winter are directly related to the genetic potential of the plant and the sequence of temperature changes to which the plant is exposed. Acclimation occurs when crown temperatures drop below 10°C (50°F). A slow cooling optimizes the opportunity for full acclimation. Should temperatures rise above the 10°C (50°F) during this phase, acclimation will pause but will resume when cooling temperatures resume. In Saskatchewan, full acclimation is usually achieved by the middle to the end of November.
Phase three represents the cereal reaching its "minimum survival temperature" for the local circumstances and year. The different winter cereals have different degrees of "winter hardiness". The conventional winter ryes acclimate to approximately -33°C (-27°F), the winter wheat varieties acclimate to approximately -22°C (-8°F), and winter barleys acclimate to approximately -17°C (1.5°F). These temperatures assume optimal management and date of crop establishment.
The final phase is the spring period of re-growth. A return to crown temperatures above 9°C accelerates plant growth and eventually results in a complete de-acclimation of winter wheat. Growth rate and rate of de-acclimation are both temperature dependent. Therefore, because frozen soils warm slowly in the spring, several weeks of warm air temperatures are required to re-establish and completely de-acclimate winter cereal plants that have survived without winter damage.
Included below are three diagrams representing three winters of varying crop stress. Diagram 1 shows a "classic" low cold stress winter where the cereal has sufficient time to build crown tissue, fully acclimates, survives winter and de-acclimates with the arrival of spring.
Diagram 2 shows where the acclimation period was initiated early, disrupted for a time, and resumed to full acclimation. In early December, a period of significant cold was experienced. The event weakened the crop, as represented by the LT50 (black line) but it was not cold enough to cause damage to the crop. The weakened crop was able to survive the remainder of the winter without any damage even though it was much more vulnerable to the cold.
Diagram 3 represents a high stress winter. This crop, grown on bare fallow, underwent the same crown growth and acclimation as the crop in Diagram 2 (seeded into stubble). In early December, the "Winter Tolerance" was first exceeded. The winter hardiness was severely impacted and later cold temperature events caused cumulative damage to an eventual Winter Kill Index of 38. Only the conventional winter ryes survived these circumstances.
Using the Model: Advanced Usage
The information copied from the Winter Cereal Survival Model below provides more detailed information on some of the advanced options. For more information, please read: D.B. Fowler and K. Greer. 2003. A web-based model for estimating winter survival in cereals[PDF].
Click on the Heading to Show/Hide the various advanced features of the website
The Management Impact Calculator
Inside the "Management Impact Calculator", drop down menus allow the user to see the impact of varietal selection and agronomic practice impact on the crop’s "Field Survivability Index" (FSI). The model assumes optimum management and the calculator makes deductions for less than optimal practices. The "Adjusted FSI" indicates how the selected cereal has been made more susceptible to cold crown temperatures. These management practices can then be applied to the model to allow the user to view the charted results.
The Winter Cereal Survival Model was created through the collaboration of Dr. Brian Fowler, Researcher at the University of Saskatchewan, Crop Science Department and Mr. Ken Greer, President of Western Ag Innovations.
Further background information can be found in Winter Cereal Production Manual.