I guess it is OK, but Iron sulfate works a bit better. It also provide Iron. Blueberries tend to develop Iron deficiency on alkaline and neutral soils. The problem with applying any soil acidifier is it doesn't work instantly and not even in one season. It took me tree years to make my blueberries happy. The sulfur itself doesn't make soil more acid. Instead it promotes certain type of bacteria, that make soil acid. And to get level of this bacterias high enough takes time. This is why Iron Sulfate comes handy - while there is not enough acidity in the soil, it gives additional iron for blueberries to take. Be patient, apply it twice a year - spring and fall and mulch with good compost. They will be happy eventually,

What you have is a good soil acidifier for blueberry. The trick is knowing how much to apply. That depends on your soil and current pH. Those two factors are best determined by running a soil test and asking for recommendations for blueberry.

It will take about a year to be fully effective. During that time the soil bacteria will convert the sulfur to sulfuric acid. The latter is what acidifies the soil.

what is your planting medium?

to trinity1911- planting medium is a combination of organic potting soil,peatmoss,pine bark pine mulch ( "a forest product") and pearlite.