So I've been planting and using dynamic accumulators for years, even teaching our farm's interns about them. Our favorite is making comfrey purin in a big 275-gal tank and fertigating the orchard with it. But this past fall, I suddenly got a desire to "look under the hood" so to speak. What exactly is the nutrient content of these plants? And lo and behold, as I know many of you are already aware, there has not been sufficient study of these plants to know for certain what's going on here.
At first this revelation made me despair. I was about to walk back all the claims I had previously made about dynamic accumulators. But then I remembered my training: in permaculture, there are no negatives. Only missed opportunities! Six months later, our farm has been awarded a research grant to study dynamic accumulators over the next two years.
In addition to summarizing the current state of affairs regarding DAs and the research we're doing, that article contains a couple of useful links. First of all, we did some serious investigation this winter and put together a list of over 100 species that practitioners around the world have reportedly used for dynamic accumulation. Big thanks to everyone here at Permies for contributing to lists on this forum. You can see our mega-list by following the link halfway down the article. If you think that we missed something, please PM me and I'll update the list.
Second of all (and this part was definitely less fun), we actually did the much-talked-about analysis of Dr. Duke's Databases, which compile all of the peer-reviewed studies known to the USDA on the nutrient content of plant tissue samples. There are a LOT of entries in there. We downloaded the whole thing, entered it all into a functional spreadsheet, and ran some numbers. We determined a baseline average for each nutrient value, and then determined threshold values that plants need to demonstrate to qualify as a dynamic accumulator. In a nutshell, a plant needs to possess over twice as much of a given nutrient compared to the average to qualify. That limits the number of dynamic accumulators to the top 10% of plants we have data for. The article I linked to above also links to the full analysis of Dr. Duke's Databases if you'd like to take a look.
The article also links to a short list of proposed dynamic accumulators that fall on BOTH lists. That's plants that both 1) are currently being used for dynamic accumulation AND 2) we can verify through plant tissue analysis that they really do possess very high levels of certain nutrients!
The next step in our research is to perform on-farm trials with six of the most promising species (in my mind at least). We wanted low-maintenance, perennial or self-seeding, cold hardy plants (our farm is in Zone 4, Northeast United States) that show up on both of the lists I described above. So we'll be studying red clover, redroot amaranth, lambsquarters, stinging nettle, dandelion, and Bocking-14 comfrey. We'll be growing test plots of these plants and tracking the nutrient content of the soil (to see if they're really "mining" for minerals deep underground, or just robbing the topsoil), and also measuring nutrient values in the plant tissue, soil mulched with the plant tissue, and liquid fertilizers made from the plant tissue.
Thanks for reading, and please let me know your thoughts! I'll post any research updates to this thread.
I’m really excited about this! Raising cuttings of comfrey was my first project after I bought this place, and after reading about the controversies around ingesting it, I began to wonder about the claims of dynamic accumulation. Heading over to read more.