Lowering soil PH for blueberries

I normally don't come to this forum on DG (I'm more of a perennial gardener, myself), but I'm posting a question here for my dad. He's planted 10 blueberry bushes and they're all pretty unhappy. He's been trying to lower his soil PH and says he can't seem to get it lower than about 6 despite adding sulfur and peat moss. (Unfortunately, he didn't amend the soil before he actually planted.)

I advised him to try pine needle mulch and working some pine needles into the soil. Beyond that, I don't know much about changing soil PH. Can anyone provide any other helpful tips?

There are soil acidifiers that you can purchased from nurseries. Green light is one brand. Sulphur takes time but it works about as well as anything. If you have a limestone soil that is well buffered, it it will be very difficult to attain and hold acidity.

That seems to be his problem--holding the acidity. He says that he can get the soil PH down to about 5.5 sometimes, and that the PH is lower when the soil is wet. I really know nothing about adjusting soil PH, myself. I grow what works best in my neutral to alkaline soil, so I don't know if it makes sense that wet soil would have a lower PH and higher when it dries.

Thanks for the tip. I'll tell him to look for Green Light.

It makes sense. The sulphur has to react with with oxygen to form oxides which in water becomes sulphuous acid, which in turn reacts with the carbonates which hold toward neutral pH. Water is necessary to facilitate all these reactions. The problem is that some soils have an almost unlimited supply of carbonates which have limited solubility in water. Example limestone.

A neighbor of mine grows blueberries. He mulches them each year with sawdust. You can buy a back of woodshavings at your local feed store. Very In expense quick fix.