A significant goal for my site has been to amass reliable information for myself, and therefore, my readers. The information I place on this site has been extensively researched before it is posted. As a physician (M.D.), I strive for scientific accuracy. I am well-versed in the scientific method and critical reading of scientific research articles. I understand the world of academia. I know, beyond doubt, the benefit this arena has provided for the world. However, I also know, beyond doubt, that there is a lot of truth that has not been proven in a lab. This may be due to many factors. To name but a few: the topic has not yet been studied, there are flaws in the design of the study, the topic is too complex for reductionist evaluation.
It is with this mindset that I readdress the concept of Dynamic Accumulators.
Within the world of Permaculture we often find reference to plants known as Dynamic Accumulators. I wrote about these plants in a previous article, but in brief, it is the idea that certain plants (often deep-rooted ones) will draw up nutrients from the lower layers of the soil, and these nutrients will be deposited in the plants’ leaves. When the leaves fall in autumn and winter and are broken down, those stored nutrients are then incorporated into the upper layers of the soil where other plants will benefit from their deposition.
So, with our scientific minds turned on, does the concept of Dynamic Accumulators hold merit?
In short, my answer is a non-comital “maybe”.
Let’s start with the scientific evidence… well, there is not much. In fact, I can find almost no research into Dynamic Accumulators. Strike that – I can find NO research into this concept at all. None. Many sources site references, but these references just don’t pan out. There are circular references, there are references to non-existing sources, and there are references to (just being honest) less than reputable books or authors. I have to be very fair and state that I am not the utmost scientific-research-article-searcher in the world, but I am pretty darn good, and my lack of results was a bit disappointing.
As it turns out, it appears that the concept of Dynamic Accumulators has been passed down and around for so long that it has been accepted as fact. This concept did not originate with Permaculture, but it has been adopted and advocated by it for a long time. So much so, that many people associate Dynamic Accumulators with Permaculture.
Well then, how did this concept get started? Where did it originate? Is there any proof at all?
This is where I back away from the cliff a bit. We do have evidence that some plants accumulate minerals in high concentrations in their tissues. This concept has been significantly researched. In the botanical community, this concept is known as Phytoaccumulation or Hyperaccumulation. There are a number of hyperaccumulator plants that can grow in soils with high concentrations of certain minerals, often metals. These plants can be grown in areas that have been contaminated with heavy metals or high-value metals. The plants pull out these minerals (phytoextract) from the soil. The plants are then harvested and processed to extract the minerals from plants to be recycled or dealt with in a more ecological manner. This “phyomining” has been used, with success, on significantly contaminated sites.
In addition, there has been an extensive database put together by botanist James “Jim” A. Duke Ph.D which provides information on thousands of plants. Specifically, and for our purposes, the database provides information on concentration of minerals found in the tissues of plants. His Phytochemical and Ethnobotanical Database is hosted on the USDA ARS site (that is the United States Department of Agriculture, Agriculture Research Service). This is a wealth of information that would take a long, long time to fully peruse and appreciate. Using the information from Dr. Duke’s database, a free, downloadable Nutrient Content Spreadsheet was created. I am not sure who created it, but I found it on Build-A-Soil.com. This is well organized spreadsheet with multiple worksheets (pages).
With this information we can connect the dots for Dynamic Accumulators. For instance, we can see phosphorus (P) concentration in Lambsquarter (Chenopodium album) is over 36,000 ppm (parts per million). This is a high concentration. Therefore, it would make sense to grow Lambsquarter on our site, let the Lambsquarter die back in the Autumn to be composted in place, and then have higher concentrations of phosphorus (P) in the Spring.
Unfortunately, while this scenario sounds good, we have no proof that it will work. Our logical pathway sounds plausible, but the reality is that Nature is never quite so simple as we would like. Minerals don’t appear out of nowhere (alchemy is still not a science!); if the soil has no phosphorus, then the Lambsquarter cannot accumulate it. If the soil has no biology, i.e. Dr. Elaine Ingham’s Soil Food Web, then there is a good chance the phosphorus may not be bioavailable to the roots. And while our scenario sounds good, we have no scientific proof (research data) that if the Lamsquarter did accumulate phosphorus it would indeed be returned to the soil in a usable form to future plants. Maybe it will, but would it take 1 year, 5 years, 25 years to become available again? This is information that we just do not have.
People will often swear by their Dynamic Accumulators. They will site their own garden as “proof”. Unfortunately, this is anecdotal information and not scientific evidence. I am not saying that their soils did not improve with the planting of Dynamic Accumulators, but was it the dynamic accumulation or another factor that caused the improvements such as mulching, composting in place, biomass accumulation, biodiversity, microclimate creation/enhancement, etc. As a good friend of mine likes to say, “The plural of anecdote is not data.”
What then should we do with the concept of Dynamic Accumulators? Take the information for what it is, soft data. That is, we can make some logical assumptions, i.e. “guesses”, and hope for the best. But we should not treat or teach the concept, the theory, of Dynamic Accumulators as scientifically proven information. We should not treat it as fact. We should definitely not rely solely on dynamic accumulation as our single solution for degraded soils. Of course, if we are appropriately applying and practicing Permaculture, we wouldn’t do this anyway.
Personally, I will continue to use Dynamic Accumulators in a holistic approach to soil improvement. It may help our soils for our intended purposes. It may help for entirely another reason. And having more diversity on our sites will almost always be of benefit… scientifically proven or not.
Note: If anyone has come across published research (not books and not anecdotes) on Dynamic Accumulators, please send me a link!
*SECOND NOTE: Due to some great input and conversation on this topic both here and on my Facebook page, I updated this article. It was published on the Permaculture Research Institute’s page here.
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