Soil Mineralisation part 3: Why and How do we Remineralise the soil?
In part 1 (1) and part 2 (2) of this series I looked at some ways in which the different elements present in the soil are connected, and how building up organic matter in soil can help to create more of the things that soil needs to be healthy. The intricate web of connections between every living thing may never be fully understood and so with soil, as with much of life, it is important to look at it from a holistic perspective if you wish to create truly healthy soil. That being said, we as humans do know and understand some things about the specific chemical elements which are necessary to soil and life, and if you know which organic materials these particular chemicals are present in it may assist you in your ecosystem encouragement. This article will explore some of the lesser-known and understood elements of healthy soil life, why they have become less abundant in recent times and what we can be doing to help to “remineralise” our soils.
What are trace elements?
‘Trace elements’ are the chemicals which are present in soil (and by extension, in our food and ourselves and, well, you get the picture) in such tiny quantities that they may be sometimes difficult to detect. Modern scientists may often favour, as Toby Hemenway put it, the “‘quantity over quality’ mindset” (3), which means that the role of these trace elements often gets ignored. As I point out in other articles, I am no trained chemist, but it seems that there are three main factors to consider when researching the trace elements present in soil.
Firstly, as I emphasised in parts 1 and 2, if you have a healthy balance of organic materials in your soil then you can probably successfully create a functioning micro-ecosystem of soil organisms with therefore healthy soil. But if this is the case, why do you need to know what the trace minerals are and how to add them to soil? Here we come to the next two factors, both of which are to do with human activity.
Modern farming is bad for soil
The second factor is that of humans trying to amend the soil to make it healthier. By isolating which chemicals are necessary to plant growth and synthesising them to make them marketable soil amendments, agrochemists managed to boost crop growth – in the short term. As Toby Hemenway reported,
“Justus von Liebig, a brilliant German chemist who made major contributions to organic chemistry and invented important chemical equipment, examined the content of ashes from grains. He found principally nitrogen, phosphorus, and potassium, and since then generations of farmers and soil scientists have concentrated on—and used staggering quantities of—these and only these as nutrients.” (3)
The result has been that in many places around the world, soils have been inundated with these three synthesised chemicals, so that the natural balance of chemicals has been disrupted:
“The roles of carbon and of the other mineral nutrients were neglected for over a century, leading to depletion of most of the world’s farmable soil and a precipitous decline in nutrition in our food.” (3)
Trace elements from other things
If we have managed to cause soil degradation from trying to make the soil healthier, what about when we add things to the soil which are not intended to improve it? Here we come to what seems to be the final important factor to consider; that of soil contamination with trace elements. This can occur from a wide range of processes, from the sinister to mundane; for examples see my ‘Chemistry’ article here (4).
So, although we can take into account the first factor that as long as we are encouraging healthy ecosystems we should get a healthy balance of nutrients, it may well be the case that the place we want to build up healthy soil has either been inundated with synthetic fertilisers, contaminated with chemical by-products, or both. In the long term, even the most contaminated or nutrient-depleted soil, if the natural balance of ecosystems is encouraged, can be restored to healthy and rich earth (see for example 5). In the short-term, however, you may well want to give this natural regeneration a helping hand, by re-adding the specific minerals which have been lost due to over-intensive chemical farming.
Many people have recognised the degraded state of our soils and have come up with solutions that involve replenishing the minerals. One prominent such organisation is Remineralize the Earth (RTE) (6), a US-based non-profit organisation founded by Joanna Campe in the 1980s (7). Their stated aim is to promote
“the use of natural land and sea-based minerals to restore soils and forests, produce more nutritious food, and remove excess CO2 from the atmosphere.” (6)
The main practical steps they seem to be encouraging for this promotion is to add rock dust to soil, since the naturally-present minerals in the rock are the same ones which have been depleted by over-intensive farming. As RTE explain,
“…Rock dusts contain a naturally occurring distribution of dozens of macro and micro nutrients delivered in mineral form. There is little or no nitrogen in most rock dust materials although essential elements for fixing nitrogen in soils such as Molybdenum and Vanadium are present in many high quality rock dusts” (8)
Where to find these minerals?
As with anything, some rock dusts are more effective than others. RTE recommend
“For remineralization the broad spectrum nutritive mineral compounds are often found in silica rich volcanic magma and ash, in sea and fresh water minerals built from remnants of living creatures such as algae, diatoms and crustaceans producing calcium and magnesium rich carbonates, in minerals derived from carbon rich humus sediments from ancient bogs, and in the natural occurring mixtures of geologic materials found in alluvial and glacial sands and gravels.” (8)
They also provide a number of sources for the rock dust on their website (9), as well as information on the ratios of rock dust to compost that you should be incorporating (8).
Is rock dust the answer for you?
Adding rock dust to soil to improve mineral content may well help to improve soil health. As a short-term way to create soil in which you can very soon successfully grow nutritious food, it may seem an attractive option. However, there appear to be a number of concerns with this method of remineralisation which need to be addressed before it can be viewed as a truly viable way of improving soil health.
Firstly, as RTE point out, there are many sources of rock dust. Most of them are not free, and all of them are either the main products or the by-products of some kind of intensive industrial process such as mining or gravel production (9). So if you want to consider adding rock dust to your soil you need to consider the financial cost and if this is going to be efficient to you monetarily. More importantly in terms of Earth Care, you need to consider the impact the rock dust is having on the earth. Even if you get the rock dust as a by-product you are could arguably be still seen to be encouraging the industrial process itself.
The main recommendation from Campe of where to get rock dust seems to be gravel pits (10); gravel is a major component in concrete production, one of the highest contributors to co2 emissions in the world (11). So adding rock dust to your soil may be accelerating the creation of a healthy ecosystem which can help to store carbon in the soil and clean the air but if you are contributing to co2 emissions in order to get the rock dust in the first place maybe you would negate this?
To sum up, if the land you are growing food in has been intensively farmed in the past, chances are it needs trace minerals added to it in order for the soil to regain its health. If you really need to use the land to start producing in the near future, then you may want to consider adding soil amendments like rock dust to the soil in order to encourage healthy and nutrient-rich food.
However, there are also the environmental and social impacts of the soil amendments themselves to consider. If the only way you can add minerals to your soil is by contributing to the earth and sky being degraded or contaminated in a different place then it may not be the best option. From this perspective the only reason why you would add mineral amendments is if you really have to get the soil healthy quicker than you could by simply adding organic matter and allowing the ecosystem to build itself. Building up a healthy soil ecosystem can lead to enriched soil within a couple of years (5) or probably sooner but in the meantime your yields may not be as large as you would like.
As with all things, whether or not you add mineral amendments to your soil is a decision you have to make for yourself. I hope this article can be of some use in the making of that decision.
1. Ashwanden, C, 2017. ‘Soil Mineralisation Part 1’. Permaculture News, 11/8/17. https://www.permaculturenews.org/2017/08/11/soil-mineralisation-part-1-need-add-soils/
2. Ashwanden, C, 2017. ‘Soil Mineralisation Part 2’. Permaculture News, 17/08/17. https://www.permaculturenews.org/2017/08/17/soil-mineralisation-part-2-major-soil-elements-can-source/
3. Hemenway, T, 2016. ‘Who Does What in the Soil’ Toby Hemenway, 29/8/16. https://tobyhemenway.com/1404-who-does-what-in-the-soil/ – retrieved 23/7/17
4. Ashwanden, C, 2017. ‘A Question of Chemistry part 1’. Permaculture News, 10/5/17. https://www.permaculturenews.org/2017/05/10/question-chemistry-part-1-ideas-effects-chemicals-rehabilitate-chemical-companies/
5. Fukuoka, M, 1975. One Straw Revolution: An Introduction to Natural Farming. NYRB Classics: New York City, USA
6. Remineralize the Earth, 2017. ‘About Us: Mission & Vision’. https://remineralize.org/mission/
7. Remineralize the Earth, 2017. ‘History’. https://remineralize.org/history/
8. Vanacore, T, 2015. ‘A Rock Dust Primer: Back to Basics’. Remineralize the Earth: Northampton, MA, USA.
9. Remineralize the Earth, 2017. ‘Resource Directory’. https://remineralize.org/mineral-products/
10. Organic Connections, 2017. ‘Why Rock Dust is the Future of Gardening’. Calmful Living. https://calmfulliving.com/project/why-rock-dust-is-the-future-of-gardening/
11. Ashwanden, C, 2017. ‘Water Farming part 2: Practical Ways to Harvest your Sky-Fruits’. Permaculture News, 18/4/17. https://www.permaculturenews.org/2017/04/18/water-farming-part-2-practical-ways-harvest-sky-fruits/
Charlotte, I am trying to work out whether it’s still worth adding minerals and micro nutrients when soil scientists like Elaine Ingham and Jill Clapperton are saying that nutrients are generally not lacking in our soil, only the soil organisms to make them available. I would be interested in your thoughts on this.
Hi Wendy! Thanks for your comment. I hope that this 3-part series has provided something of a balanced view of soil minerals, their source and role. However as you say, it is not only minerals which are needed in order to create healthy soil; it is the micro-organisms which use the minerals. As I mentioned in my articles, building up soil through addition of organic materials such as plant matter can be a very effective way of reviving the rich ecosystem which is needed in order for soil to be healthy. This is especially true if you consider what you are adding to your compost and try to get a balance of plants which are rich in nitrogen (such as N-fixers like the Fabaeceae family), calcium (Dynamic Accumulators), carbon (brown plant matter), etc. Another important thing to consider especially in the design process is the addition of ‘living mulch’ plants such as comfrey or nettles, which can be present growing in your system as a readily-available source of soil nutrients.
So with all this in mind, is it ever worth adding chemicall-isolated soil amendments? As I said in this article, it’s possible that if your soil has been degraded by chemical input then the building up of healthy soil through addition of organic materials may take a long time. If you require healthy soil more quickly you may consider adding something like rock dust to accelerate the process. But even then I think it is important to look at the ethical and environmental costs of such mineral addition, and ask yourself, ‘Do I really need healthy soil that quickly? Can I wait until the ecosystem rebuilds itself through addition of locally sourced, organic materials?’
The answer is for you to decide.
I hope this helps.