Recording the flowers per vine in late Spring/early Summer allows you to do an early prediction of your total yield. It’s only an approximation as a heavy hail storm during flowering, or rain all Summer long can really affect the yield. However it’s good to do these estimates so you can start planning at least for maximum predicted yield quite a few months before harvest.
The app makes it very easy to count flowers per vine as you put an RFID tag at a each of your sample sites. When doing a flower count, scan the tag and then enter the number of flowers you count on each vine for the next 10-20 vines (depends on your sampling system). Sync when back in the office and you will see the average flower count per block online straight away.
You need to know two other metrics in order to predict yields:
- The average historical bunch weight per variety.
- Expected percentage fruit set.
The longer you are collecting data, the better your bunch weight prediction will get, but to start with there are generalised predictions you can find online according to variety. Or maybe ask local vintners for their predicted bunch weight and percentage fruit set. Percentage fruit set is around 50% or for predicting the maximum yield you can use 100%. Here is a good article detailing the reasons for variation in fruit set. You can later count bunches per vine after fruit set to improve your yield prediction and get a picture of your fruit set percentages for future years.
Use the flowers per vine count combined with percentage fruit set to estimate the no. of bunches per vine. Then you can use the below formula to get an early prediction.
Yield (kg/block) = actual number of vines per block x no. bunches per vine x bunch weight (kg)
NB: actual number of vines per block = expected total number of vines in block – the number of dead/missing vines in block