Foliar Nutrition at Bloom in Blackcurrants

Molly Shaw, April, 2026

Executive summary

This trial indicated that fruit set can be improved by foliar application of nutrients/biostimulants, particularly in situations those with limiting soil health.  Therefore a foliar nutrition program seems to be reasonable investment for farmers to make.

Increased fruit set in treatments indicates that either micronutrient availability is limiting fruit set, or that the plants are responding positively to the biostimulant additives in the foliar nutrient programs, or both.

This increased fruit set was experienced despite soil nutrient levels testing in the sufficient range.  Tissue testing showed either a very slight increase in Ca and B (foliar), or inconsistent changes (flower).

Increased fruit set did translate into increased harvested yield.

There were large differences in fruit set and yield between the four farms, which were not explained by simple soil or tissue nutrient testing.

• We believe that underlying soil health is a key component of high bush health which leads to high fruit set.  While foliar nutrition programs can improve fruit set and are useful, alone they can not make up for compromised soil health. 

The full project report is available upon request.