Off topic but still an energy post. Both heavy duty and alkaline batteries use carbon and zinc electrodes but heavy duty batteries use an acid electrolyte and alkaline batteries use (you guessed it) potassium hydroxide. Alkaline batteries are mucho superior in every respect except initial cost and I never knew why until I saw your post. You do NOT want your electrode, in this case zinc, dissolving in your electrolyte.

Nickel Iron batteries, touted by one of us, last essentially forever because the electrodes are essentially insoluble in potassium hydroxide. They have other issues, but they last forever.

I shoulda known quoting from my Permaculture class. However, the pH and Aluminum problem is still around 3.5 pH when no plant can survive. The issue relates to the interaction between Phosphorus and Aluminum across a spectrum of pH.

http://www.plantphysiol.org/cgi/reprint/18/4/708.pdf

I'm sure there are other references out there.

Yes, water logged soil is indeed anaerobic. I'm trying not to write a book inside a comment, so have compressed the whole process of tilling, fertilizing, biocides, etc that comprise our conception of food "production" as fundamentally flawed and always ends in depleted soil and desertification.

PH of 4.5 is a bit too late

http://www.tropicalforages.info/key/Forages/Media/Html/Desmodium_heterocarpon_subsp._ovalifolium.htm
Extremely well adapted to low fertility, acid soils (pH 4-7), with high Al and Mn, and low P.

Let's not split hairs to fill in the 0.5 pH to go. It's out there, if you want to find a plant that "survives" it. However, below 3.5 is certainly a dead zone.