In March, the currants wake up, and your actions now will determine whether the harvest will be meager or such that the branches will bend under the weight of giant berries.
Most gardeners sprinkle ash or urea under the bushes, but there is a much more effective method.
All you need is regular baker's yeast, which you can buy at any store for pennies. It starts processes in the soil comparable to the action of expensive humic fertilizers, but works faster.

Dissolve 100 g of fresh yeast in 10 liters of warm water, add 2 tablespoons of sugar and leave to ferment for 3 hours.
Then spray the currant bushes, paying attention to the underside of the leaves and buds.
Yeast fungi activate the soil microflora, helping the roots absorb potassium and phosphorus - these elements are responsible for the size and sweetness of the berries. In just a week, the buds will swell more than usual, and the young leaves will become bright green.
But there is a catch: yeast "eats" potassium, so 3-4 days after treatment, sprinkle ash under the bushes (a glass per plant) or water them with banana infusion. Otherwise, the leaves may turn pale.
The second important point is that you need to spray before the buds open, while there is no active sun. If you do it later, the solution will burn the young foliage.
To protect against kidney mites, add 1 tablespoon of dry mustard to the yeast solution.
This will not harm the plant, but will drive away pests that often destroy the harvest.
By the way, you can water gooseberries with the same solution - their berries will also become noticeably larger.
And if you repeat the spraying after flowering, the currants will fill out faster, and you will harvest two weeks earlier than usual.