shazaam:

I never could find any. They don't sell it in our small town.

That's too bad -- I guess I'll have to do the experimenting myself for a change. :) Actually, I did try incorporating cottonseed meal in my blueberry potting mix this spring. The bushes did very well, but I also fertilized periodically with a weak MirAcid solution...so it's hard to draw any firm conclusions.

There's one other question that I've been wanting to ask you, as well -- when you fertilize potted blueberries with ammonium sulfate, are you also supplementing with something else to provide P, K, and micro nutrients?

Mine have done fine with only ammonium sulfate. My mix has been composted rat litter. Apparently that has enough of everything else to grow great blueberry bushes.

Other plants fertilized with a complete fertilizer for acid loving plants have done about the same. Now I can't find that anymore either, the Osmocote brand.

Look for cottonseed meal in a feed store, not a garden center.

I've used a lot of it over the years on blueberries with seeming success.

Thanks for your replies, fruitnut. I'm hoping to experiment with fertilizing regimens next year, and your results with ammonium sulfate are very impressive. Tentatively, I'm going to compare at least one synthetic/chemical approach using tapla's 5-1-1 potting mix and one organic approach using a modified version of the 5-1-1 mix that includes leaf mold and cottonseed meal. I might experiment a bit with containers, as well. My plants in plastic pots have done very poorly compared to those in terracotta and fabric pots, and I'd like to see if that's a limitation that I can overcome or whether I should forego plastic entirely.