A quick one...
12.1 + 6.7 / 2 = 9.4 not 8.8.
Well yes and no
If you're working Growth Degree Days out for yourself that's exactly how you'd do it. But the Syngenta GDD calculator takes the average for every hour of the day and works out an average for each, it then looks at the whole day and skews the average to ensure it really is representative of the day.
So if you have day with a high temperature of 10c and a low temperature of 2c but the majority of the day was closer to 2c then the average figure used would be closer to 5c than 6c.
It really is a clever bit of math and I agree at first glance it can look a little odd but it is more accurate.
(Take a look at my blog here about the difference between 0c and 6c for GDD).
Although the way this is worked out is more accurate than a normal calculation, I'd still add the following advice:
Use GDD as guide to help with your PrimoMaxx applications,
- In the summer apply every 2 weeks
- In the cooler months apply every 4 weeks
- In between - let the GDD calculator guide you