Fertilizer for Acer palmatum 'Atro-purpureum'

Could someone suggest a good fertilizer for a young potted Acer palmatum 'Atro-purpureum' 12" high and 7" wide besides Osmocote? I read somewhere that Osmocote will leave a residue in the soil if used for any long period.

 

I use a commercial mixture of seaweed extract and fish emulsion. The availability of this stuff seems to vary locally. One brand that seems to be widely distributed is Neptune's Harvest.

 

Thanks for the info.

 

What is your planting medium deficient in? That will give you an idea of what needs to be augmented.

 

I recently transplanted the Acer palmatum 'Atro-purpureum' into some naturally enriched potting soil, 0.14-0.09-0.02 which it seems to feel comfortable in since it's getting alot of new leaves. I received this as a gift and do not know very much about Japanese Maple trees.