Ramble:

Short answer: throw it on top. If you have a good mulch, little or no fert should be needed. If the fertilizer is water soluable, then throwing it on top is the same as putting it under the mulch. If not water soluable, then maybe incorporated into soil under would be better.

Throw a little on top and don't worry.

The Fruitnut

Ramble:

As Fruitnut says, this is not an either/or situation. You can do both -- whatever is more convenient for you. Most fertilizers I know of are water soluble, and will eventually dissolve and reach the soil. But I also agree with Fruitnut that, if you are mulching adequately, raspberries and blackberries need little to no supplemental fertilizer. I don't use any on mine, and they grow just fine with stable manure around the surface.

If you are going to put chemical fertilizers around blueberries, avoid any that are nitrate-based. Blueberries do no like them. Pure ammonium sulphate is the only chemical fertilizer I would use around blueberries. Blueberries also respond well to iron sulphate, if you can find any of that at your local nursery.

Don Yellman, Great Falls, VA

How about Sulphur to reduce PH? I've read you need to scratch this into the surface. So do you need to remove mulch for the Sulphur (or the Iron too)?

Oh for heaven's sake, Ramble, just pull the mulch back and scratch the sulphur into the soil. This is the kind of fine-tuned guidance that falls in the category of common sense. We may have to assign you an assistant gardener.

I pull back my mulch before scratching in iron sulphate. Trouble is, I can't find iron sulphate any more. Now that's a problem.

Don Yellman, Great Falls, VA

Iron sulfate

I find that even good farm and garden places can have it and not know it. It is labeled "copperas."

>If you are going to put chemical fertilizers around blueberries, avoid any that are nitrate-based.I know that is good advice, but it always suprises me that old commercial blueberry growing literature used to advise fertilizing with "bulldog soda" in summer after fruiting to get a burst of growth. Sodium nitrate would seem the worst fertilizer for blueberries.