Wet soil conditions
Boron is a very mobile nutrient which can be easily leached in wet years or made unavailable to the plant in dry years.
Boron is a key nutrient in the movement of the GABA hormone needed to fertilize seed. Without the daily movement in the pod of GABA seeds do not set- missing seeds in the pod.
High Sulphur application rates
Boron availability to the plant can be reduced by excess sulphur application since sulphate and borate compete for uptake at the plant root surface.
Boron movement within the canola plant differs between canola varieties making some varieties are more sensitive to Boron deficiencies than others.
Boron availability to the plant is reduced on soils over pH of 7 and under pH of 5.5. Boron deficiencies increase on sandy soils, low organic matter soils and highly weathered soils.