probably other types from other places. I don't think there is a
significant difference in the mineral content of one source compared
to another. I do not deny that there may be differences in how well
the packers processing method preserved kelp's multitude of
beneficial complex organic chemicals that improve the growth and
overall health of plants by functioning as growth stimulants,
phytamins, and who knows what else.

Still, I prefer to buy by price, not by mystique, because, after
gardening for over twenty years, garden writing for fifteen and
being in the mail order garden seed business for seven I have been
on the receiving end of countless amazing claims by touters of
agricultural snake oils; after testing out dozens of such
concoctions I tend to disbelieve mystic contentions of unique
superiority. See also: _Seaweed_.

_Leather dust_ is a waste product of tanneries, similar to hoof and
horn meal or tankage. It may or may not be contaminated with high
levels of chromium, a substance used to tan suede. If only
vegetable-tanned leather is produced at the tannery in question,
leather dust should be a fine soil amendment. Some organic
certification bureaucrats prohibit its use, perhaps rightly so in
this case.

_Leaves._ Soil nutrients are dissolved by rain and leached from
surface layers, transported to the subsoil, thence the ground water,
and ultimately into the salty sea. Trees have deep root systems,
reaching far into the subsoil to bring plant nutrients back up,
making them nature's nutrient recycler. Because they greatly
increase soil fertility, J. Russell Smith called trees "great