Originally posted by Mike Bradbury
Leather meal is a byproduct of processing leather and a cheap sourse of nitrogen for fertilizers. Since it's part of animal skin it is "organic", but because of the tanning process it's full of heavy metal contamination. Lots of the materials are like that. No other use for them so they are very cheap to buy in large quantity.....
If a product kills bacteria and soil microbes than it doesn't matter if it comes from dead dandelions, you don't want to use in a "organic" program. Think "sustainable horticulture" rather than "non petroleum based ferts" and you'll have 1/2 the battle won.
WOW! I learn something from someone every day. Thanks Mike for writing about this. I have never specifically suggested someone use leather meal but I always include it in my list of organic sources or protein. But no more of that!
My first thought when I read what you said was, 'why would someone go to the trouble of tanning leather and then turning it into leather meal?' What I found was that the leather meal on the market is the BY-product (otherwise known as waste) of leather tanning. They don't just make leather meal out of perfectly good hides. The stuff that falls on the floor in the tanning industry gets swept up and becomes leather meal! And it is full of chromium to very high levels.
I did also read that the chromium in the leather is not the kind that is available to plants. However, in an organic program, lots of things that are not immediately available get 'attacked' by the abundance of humic acids and suddenly become available in spades! That has been part of the beauty of healthy organic soil. Now I see it can work both ways.
So thank you again, Mike. This info has been mentally bookmarked. Just to make sure, I will also bookmark the site I found the info on. Not only that but I'm going to send out a message to all the gurus I know about this. Frankly I'm a little unpleasantly surprised, but not shy to adapt to the new info.
Here is the conclusion from the above link.
The reviewers agree in the determination that leather meal that is a by-product of a chrome tanning process is a synthetic substance and that it should be prohibited for use in organic agriculture. The reviewers agree that there are many alternatives available to this product. Although reviewers have mixed opinions about the dangers posed by addition of chromium(III) to the soil, they agree that addition of metals not required for plant nutrients is contrary to organic principles and NOSB recommendations. In addition, other metals such as lead, as well as solvents, preservatives, dyes, and other additives from the production process pose concerns.