| | Jane West works for a grain marketing company and is trying to forecast which areas in Alberta harvest will start first. She wants to use the Weather Mapper to monitor canola growth throughout the province, by measuring the number of growing degree days. Growing degree days are calculated as follows:
Daily GDD = ((Tmax + Tmin) ÷ 2) - Tbase
where:
Tmax = the daily maximum air temperature
Tmin = the daily minimum air temperature
Tbase = the GDD base temperature for the organism being monitored
.
Jane wants to use the Weather Mapper to learn the following things:
- Which areas of the province have accumulated the most growing degree days to date?
- Which areas of the province will accumulate enough growing degree days to start harvesting first?
Process:
- Select "Weather Mapper"
- Select these choices from the drop down menu under query:
Step 1, select a category: Growing Degree Days
Step 2, enter a start and end date: Only data from current year and previous year is available
Step 2, choose a base temperature: Choose a base temperature of five.
Step 3, select a colour scheme: You can leave the colour scheme as default, or choose a scheme from the drop-down menu.
- Click on "Get Data & Refresh Map".
- Click the print icon near the top of the map.
- Select "OK" in the pop up box
- In the new window that appears, select, "File" - "Print".
Jane can now see which areas of the province have accumulated the most growing degree days to date. She then cross-references the Weather Mapper with the table below that shows the number of growing degree days needed for each crop stage:
| Stage | Stage Description | Stage Details and Phenological Code | Accumulated GDD Needed After Seeding Date. |
| Emergence | Cotyledons completely unfolded | Cotyledons completely unfolded. 1.0 | 152-186 |
| Leaf Stages | Two leaves | Two leaves unfolded. 1.2 | 282-324 |
 | Four leaves | Four leaves unfolded 1.4 | 411-463 |
| Flowering | Flowering begins | At least one open floret on 50% or more plants. 6.0 | 582-666 |
| Flowering 50% complete | 50% complete. 6.5 | 759-852 |
| Seed fill | Seed fill begins | 10% of seeds have reached final size. 7.1 | 972-1074 |
| Maturity | Seed begins to mature | 10% of seed has changed color 8.1 | 1326-1445 |
| Swathing | 40% of seed on main stem has changed color | Swathing recommended at this stage. 8.4 | 1432-1557 |
Canola (B. Napus)
Data source: Stu Brandt, Scott, SK 1993 - 97 and Perry Miller, Swift Current, SK 1995-98
Stage GDD degree Celsius
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