Rather than focus on how many blank pods may be present, concentrate on yield assessment by examining the components that contribute to yield (number of plants in a given area, number of pods per plant, number of seeds within the pods). The following equation can be used to estimate yield when seed size has a thousand seed weight of 4.4 grams:
Yield estimate (bu/acre) = # pods per plant X # seeds per pod X # plants/sq ft X 0.00084
For other seed sizes, the number of seeds/square foot in 1 bu/acre and the conversion factors for the above formula are as follows:
g/1000 seeds 1bu/acre – seeds/square foot bu/acre conversion factor
2 261 0.0038
2.5 208 0.0048
3 174 0.0057
3.5 149 0.0067
4 130 0.0077
4.5 116 0.0086
5 104 0.0096
The thousand seed weight (TSW) for your variety was written on the seed bag but remember the average seed size in a canola field is normally much less than that of the seedlot due to small seed in late branches. Stresses such as hot, dry weather during seed filling can also lead to lower TSW.
Variability with this calculation can be huge so the more samples taken across a field, the more reliable the estimate. As a result, a large number of yield estimates should be taken across the field (approximately 25 to 50) to be within + or – 25%. One helpful tip is that you don’t have to shell out pods to count seeds, you can often hold the pod in front of the sun (wear sunglasses) and you will see the individual seed outlines.