You might be able to just replenish with CRF....but you might want to add a little more Lime, or add the Gypsum (and then supplement with Epsom Salts when fertilizing throughout the season). I have Citrus in modified 5-1-1, and I haven't refreshed the Lime for a couple years. Now I simply make sure to fertilize regularly, and I sprinkle more Osmocote into the top inch of bark every few months (4 - 6 months or so). Josh

JAG, can you elaborate on the idea that pH is not as important for blueberries in pots as in the ground? Al, do you concur? Yes - I do. Mineral soils in general hold nutrients much more tightly than the highly organic soils we grow in. If you'll consider: Even the gritty mix I often use is still highly organic at 2/3 inert ingredients: 1/3 (33%) bark as compared to the sandy soils the BBs are usually grown in with an extremely low organic component (usually Fertilizers affect media solution pH and make it easier/more difficult for certain types of plants to extract nutrients from soil solutions. Often, the plants themselves add ions to the solutions to actually change solution pH and make it easier for the plant to take up ions. The fertilizers we would want to use for blueberries will have an acidifying effect due to the ammonium nitrogen content. Fertilizers that form acids will be high in ammonium, ammonia, and urea. During nitrification, ammonium is converted to nitrate in the media, and in the process H is released which lowers pH. Plants also secrete H into the media whenever they absorb ammonium. Fertilizers containing nitrate in the form of calcium/potassium/magnesium/sodium nitrate all tend to cause an alkaline reaction and raise container solution pH. Although the most important factor in where media solution pH will fall is the alkalinity of the irrigation (which includes the fertilizers added) solution, it's not the only factor. We need to not only consider the fertilizer, but also the pH of the medium components, the liming materials used in the medium, and the pH/alkalinity of the irrigation water before adding fertilizers. Finally, the gritty mix should be fine for BBs if you use gypsum as a Ca source. You'll need to water fairly frequently if you use it, though. Turface and granite are both mildly acidic, and the bark will be around pH 4.5-5.0. Al

My suggestion is to worry more about where soil solution pH is as a generality and less about chasing a particular medium pH, which I'm absolutely sure will end in frustration anyway. If you use a fertilizer that derives its N from urea (not nitrates) and neutralize your irrigation water's alkalinity with vinegar if you suspect or know alkalinity is high, you'll be just fine. Container media pH is nowhere near the issue that the pH of mineral soils is. From something I left on another post: BBs have some pretty unique nutritional requirements compared to most other plants. They grow in acidic soils where fertility is usually quite low. Also, the predominant form of available nitrogen (ammonium) is usually present at levels that could be toxic to many plants. However, BBs have mechanisms to cope with the acidic, ammonium-rich, nutrient-poor conditions. They form a symbiotic relationship with certain fungi, which derive carbohydrates from the inner portions of the BB root system, and in return, help extract nutrients (especially phosphorus and nitrogen) from the soil for the plant. So, in comparison with many other plants, BBs have very low nutritional requirements. In fact, they can be quite sensitive to high levels of some nutrients, and a heavy fertilizer application can injure them, so be sure you fertilize at reduced recommended strengths (1/4 - 1/2 strength, weekly to bi-weekly). BBs also have the unique ability to directly absorb ammonium ions. Most plants absorb N in nitrate form, which is then converted to ammonium by a metabolic process before being incorporated into proteins. However, nitrate fertilizers can be harmful to BBs. For this reason, ammonium forms of fertilizer are recommended, such as ammonium sulfate or urea. Ammonium sulfate is particularly good because it acidifies the soil, and most soils tend to have a pH higher than 4.5. (Foliage-Pro 9-3-6 offers 2/3 of its N in nitrate form, which is normally a good thing, but not particularly desirable for BBs.) In another thread, someone made the comment that there is no Ca in fertilizers for acid-loving plants because they don't like it. JaG appropriately pointed out that ALL plants need Ca, which is true. The reason there is no Ca in most of the fertilizers we use on container plants is simply because of solubility issues. The fact that different species of plants tend to grow on different types of soil does not mean that the one needs more of a certain nutrient than the other. It just means that the plants have developed strategies to adapt to certain conditions. Acid-loving plants have adapted to acid soils. Their need for calcium is still the same as any other plant, and their nutrient requirements do not differ from plants that thrive in alkaline soils. The problem for acid-loving plants is that they have not developed a method to limit their calcium uptake, and will absorb too much of it when available, resulting in cellular pH-values that are too high. Some acid-loving plants also have difficulties absorbing iron, which is tightly bound in alkaline soils, another reason why they thrive in low pH soils. This all pertains to the plants ability to handle nutrients, not to the actual nutrient needs of the plant. Filix is concerned (remember, this is off topic slightly because it was addressing issues being discussed on another thread)about micro-nutrient availability if he uses the MG 30-10-10. It contains all the micro-nutrients that are likely to be deficient in container soils, but glaringly absent are the secondary macro-nutrients Ca and Mg ... S as well is missing. Supplying the Ca with gypsum and the Mg with Epsom salts is probably the best plan. Though insoluble, enough S can be had by including a tsp of elemental S per gallon of soil. Al

The gypsum doesn't actually raise the pH in most soils. However, it's still a good amendment for two reasons. The problem most plants have in very acidic soils is that plant toxic aluminum is soluble when the pH is below approximately 5.4. The sulfate from gypsum combines with aluminum, making it less phyto-toxic. Second, gypsum supplies soluble calcium, often lacking in highly acidic soils, to plant roots.