FWIW, I found this on the Espoma website.

Mix one part Holly-tone to 30 parts potting soil when planting. Feed established plants 1 teaspoon of Holly-tone for each 4 inches of pot diameter.

This seems like a really high rate. Has anyone followed this advice with good results?

I wouldn't use the Holly Tone. Granular organic fertilizers are not very effective or efficient in a container growing situation. They need to be digested by soil organisms before they are converted to a soluble salt form that the plants are able to take up thorough their roots. And in a container mix like you describe, there are simply not the populations of these organisms present to be able to make this conversion effective. Most of the fertilizer will just go to waste.

You can add some sulfur to increase acidity/lower the pH of your mix (I'll leave it to Al or others to suggest appropriate quantities) or look for the Osmocote product formulated for acid lovers.

That's really OK with me if the Holly Tone breaks down slowly. I'm including it in my soil mix as a slow release fertilizer. As I said, I will be supplementing with Miracid. I already have the Holly Tone and am trying not to spend any more money on amendments, like the osmocote.

Regarding the osmocote, from the information I could find it looks like the nitrogen is derived from ammonium nitrate. My understanding is that blueberries are sensitive to nitrate, so I'd hesitate to use it in these containers.

The point I am trying to make is that granular organic fertilizers - the Holly Tone - don't really break down in a container situation. So you are gaining no benefit to the plant by using them.

Nitrates are going to be a result of any source of N you apply. They are formed during the nitrogen cycle in a stage known as nitrification and are one of the primary forms N is taken up by the plant. A controlled release fert like Osmocote is not going to overwhelm the plant with nitrates. I use it with my container blueberries and have never noticed any issues.

Soluble fertilizers also need bacteria to make nutrients available. Urea needs to be broken down by bacteria containing the enzyme urease to make available to plants. Also blueberries can be hurt by nitrates do not use osmocote if it has nitrates. How nitrates hurt blueberries is well documented. The plant produces an enzyme that is not efficient in removing nitrates and using nitrates can lead to toxic levels. Any acids fertilizer will be OK. Holly-Tone will give you amazing results with blueberries in containers. The best plants I ever saw were fed organics. bboy1977 uses only organics and his plants are amazingly nice.
It is a myth that organics will not breakdown in containers. Bacteria are everywhere. Even when soils become bone dry, within 24 hours of watering bacteria are teeming in the soil. Bacteria can produce over 1 million generations in 24 hours, and are fine in dry soils, as they can revert to spores which will not die in bone dry soils.

Here is a tutorial on nitrogen explaining how they differ,

https://www.extension.purdue.edu/extmedia/AY/AY-204.html

I would avoid using nitrates for containers as you are polluting the environment big-time!

Thanks, drew51. I agree completely that there's no reason to believe microbial activity is too low in container for organic granular fertilizer. I just didn't have the time or energy to argue against the answer to a question I didn't ask.

I appreciate you pointing me in the direction of bboy1977. I'll have to look through his post history and see if he mentions how much holly tone he uses.

You can of course do as you wish. But those who focus on container gardening understand that you will get very inconsistent and mixed results using granular organic fertilizers. In addition to the lack of adequate populations of microorganism to process these types of fertilizers, they typically lack most, if not all, of the micronutrients, which are found in the mineral based soils that are missing from container soils. Where are those being supplied from?

It may also be helpful to read this thread where the discussion is detailed and in depth. But sometimes we just like to do what we want to do despite competent and knowledgeable evidence to the contrary.

"I would avoid using nitrates for containers as you are polluting the environment big-time!"

Would you care to explain this statement as the logic eludes me. I fail to see how fertilizing containers with anything will pollute the environment.