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I know that blueberries need soil in the range of ph 4-5, but no one ever says why they need the pH in that range. I've heard that it may be because of a lack of available iron at higher pH, and that other plants emit acidic in their root zone to create iron that they can use. So is it all about the iron? This chart of nutrients avaiable by pH is also interesting...it looks like the only nutrient available at low pH is iron. But if iron is the limiting factor, it looks like it is available up to pH 6.5. So why the pH 4-5? enter image description here

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This might be more appropriate on Biology, but I'll wait and see if the community here agrees with me. Related meta post: meta.gardening.stackexchange.com/questions/291/… –  Niall C. Jul 22 at 15:22
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The answers are a fundamental necessity to understanding how your garden can be more productive, so it belongs in both actually. –  Fiasco Labs Jul 22 at 15:29

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Blueberries have a rudimentary root system that doesn't have the finer root hairs found on most plants.

They grow best in forest duff (lots of acidic, organic matter). The acidic nature of the soil causes bacteria and fungi to thrive that release minerals and ammonia that blueberry bushes thrive on and that their roots can readily absorb.

In plant root systems it's more about symbiosis and the nutrient pool it creates than the measurable byproducts (acidity, nitrogen, etc.). The main difference between woodlands and gardens is the method of nitrogen uptake (ammonia vs. nitrates).

Neutral to very slightly acidic soil tends to be a nitrate rich source of nitrogen, with mostly bacterial activity (the rest of your garden), whereas acidic soil favors more fungal activity and an ammonia rich environment for the nitrogen source. Acidic soil also hosts acid loving bacteria (which that chart doesn't address) that directly attack mineral in the soil to release phosphates, iron, magnesium which your blueberries love. The iron particularly is needed to prevent chlorosis so the leaves can create enough chlorophyll.

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Great answer! Are there some links or books you can recommend for further reading? –  Eric Johnson Jul 22 at 21:02
    
    
It was a book about the soil food web. The most interesting parts were about grassland, forest and garden biological environments and how each could be adapted to use on your property have a better lawn, shrubbery and garden area as each is a distinct ecosystem with specific soil requirements to promote root health and nutrient availability. Wish I could remember the name. –  Fiasco Labs Jul 22 at 21:22
    
I still don't understand how blueberries can grow all over the area I live in which has alkaline soil with ph over 7 due to the limestone deposits. –  kevinsky Jul 22 at 22:33
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@kevinsky Blueberries in my experience can take more alkaline in colder climates (for whatever reason), especially in almost pure organic matter. Also, decomposition produces acid, which may neutralize quickly, but keeps the root region slightly acidic. –  J. Musser Jul 22 at 22:44

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