Soil Mineralisation part 2: Major Soil Elements and Where WE Can Source Them
In part 1 of this article, I discussed why you might want to change the chemistry of the soil you are working with, and how, although humans have developed a number of useful ways of identifying which chemicals are present in soil and how these interact with each other to make balanced soil, we do not know everything about these interactions. The upshot of this is that even though isolated chemical amendments are available which you can add to soil, these are no substitute for the full-blown ecosystem which exists when you add many different kinds of organic matter to compost. On a website such as this, the previous statement may sound a little like it’s preaching to the converted, though it seems important to point it out anyway, since there are a lot of so-called ‘natural’ or ‘organic’ soil amendments out there too, which although they may not be as degrading of the land or poisonous to the ecosystem as straight-up synthetic chemicals, may still be ultimately unbalancing for your soil. You can decide for yourself what is best for you to use; below I shall go into the main chemical “players” in the wonderful theatrical piece which is soil life, how they interact, where they can be found, and whether or not you should buy any products which claim to be able to build soil using them.
Chemicals and their parts
In Toby Hemenway’s trio of articles ‘The Cosmos, The Earth, and Your Health – The Story of Soil’ (1, 2, 3) he begins by exploring how modern science theorises that the chemicals essential to life on Earth first formed back in the old days when the Universe was young. He likens this introduction to that of “the main players” of the drama of life, in which there appear some recognisable characters, each with their own quirks and unique parts to play. I go into these roles briefly in this article; readers are encouraged to search for more information in the original.
To continue Hemenway’s dramatic analogy, the elements which need to be present for healthy balanced soil could be categorised into two groups of “main players” and ‘supporting roles’. This is in terms only of the quantity of each element which needs to be present for soil to be healthy rather than in terms of importance; as explored in part 1, all the elements involved have their own importance as part of the holistic web.
The backbone of life
The first of the “major players” is carbon, “the backbone of life” (3) because it is “uniquely multifunctional” and can “construct vastly more [compounds] than any other element on the planet” (3). When it comes to soil, there appear to be two major things which carbon can do; firstly, being able to bond with other elements to create new compounds and secondly, “It can store lots of energy when it bonds to itself, and then release that energy when those bonds break” (3).
As Hemenway put it,
“Soil lacking in carbon—in organic matter and the soil life it breeds—is dead soil, and it creates dead food”. (3)
Some holistic ways to add carbon to your soil include adding any kind of dead organic matter to compost, such as dry leaves or grass, or even sawdust, woodchips or cardboard – though it is probably a good idea to check these latter examples to see if they have been treated with chemicals, and also to consider whether the sources you use for them are impacting the environment beneficially – for more information on this you can check out my article here (4). You can also use carbon-rich materials as mulch, either by bringing them into your system from another part, or by using the “chop and drop” method of cutting parts from growing plants and leaving them to dry up on the ground, so that their nutrients are more easily accessible to the soil (see for example 5).
Protein and photosynthesis
The next three Hemenway mentions are the elements which have been most researched and promoted as essential to healthy soil by agrochemical science, i.e. nitrogen, potassium and phosphorous (3).
Nitrogen helps to build protein and is also “a major ingredient in chlorophyll” so is essential to plants being able to photosynthesise properly to convert sunlight into food. Though “much-touted”, it is important to remember that it is often “so over-emphasised that other nutrients just as valuable get overlooked” (3).
Some holistic ways to add nitrogen to your soil include adding any kind of green material to your compost (6, 7), such as freshly cut plants. Manure is also rich in nitrogen, in particular chicken manure and that of grazing animals such as cows, sheep and goats (see for example 8). Some plants are more nitrogen-rich than others, most notably the ones which have the ability to “fix” nitrogen through nodes in their roots, which includes most members of the Fabaceae family such as beans, peas and locusts, as well as many Eleagnaceae species such as Sea Buckthorn (Hippopheae Rhamnoides), Wolfberry (Eleagnus Commutata) and Goumi Berry (Eleagnus Multiflora) (6). As well as using the green material from these species in your compost, a very effective and holistic way to use the nitrogen they “fix” is simply to plant an abundance in your site, as, simply by growing, they can make this element accessible to other species growing nearby.
Another very energy-efficient way to boost nitrogen levels (in terms of proximity of source) is to add human urine. You have to make sure you dilute it or it will be too strong for your plants. For more information, you can see this article (9) or the book ‘Liquid Gold’ (10).
Adding bits of animal?
Phosphorous “stimulates root formation, improves flowering and seed production, strengthens stems and stalks, aids nitrogen-fixing bacteria, and increases disease resistance” (3)
Some holistic ways to add phosphorous to your soil can include by sprinkling “bonemeal” into your compost or sheet mulch; blood and other animal remains are also high in phosphorous. If you do not have access to such things as part of your system it is possible to purchase organic phosphorous-rich soil amendments such as rock phosphate or bonemeal powder. However, the ethics of such industries could be seen as questionable and possibly contradictory to the permaculture ethics. With animal products the controversy is perhaps clearer to see; where did the animals come from whose bones you are using? What kind of lives did they lead? How much energy went into keeping them caged, feeding them imported feed, slaughtering them and then transporting their remains to your garden? If the answers seem unknown or not very energy efficient you may wish to reconsider buying such products.
Although the production of rock phosphate does not necessarily involve cruelty to animals it still represents a sizable industrial process (11), and phosphate mining has its own detrimental ecological consequences (see for example 12). You may also wish to consider investigating whether or not the human rights (see for example 13) of those working in or around the mines are being respected as part of the ‘People Care’ ethic.
Luckily for those concerned with the sourcing of commercial phosphate products, you can use instead crushed egg shells, soy bean or other nut husks and shells, and banana peel (assuming you have these as a waste stream in your system anyway; otherwise, again, the energy efficiency may be in question)(6), or bat guano. If bats are native to your area you can try installing habitats for them in order to catch the guano and harvest it yourself as Jonathan Engels suggests (14). This would also bring all the other benefits which bats can have to your system, such as pest control (15).
Careful with the alkaline…
Potassium is the final of the three most popular commercially isolated chemicals, though Hemenway says its “role is less well understood” than nitrogen and phosphorous (3). What we have discovered is that it “is needed for many enzymes to function, and it helps young plants get started, in part by strengthening roots”. (3)
Some holistic ways to add potassium to your soil can include using wood ash as part of your compost or sheet mulch mix. A lot of the natural materials which contain a lot of phosphorous are also high in potassium such as bonemeal, blood and eggshells (6), so if you have found a good source of these you can use them for both types of nutrient. Hemenway points out that if you add too much potassium it can have the effect of making the soil too alkaline, especially if you are using a heavily alkaline source such as wood ash (2). He recommends testing your soil if you are not sure what pH level you are dealing with – this article has some ideas for how to do this (16).
A forgotten star?
Hemenway describes calcium as “a neglected nutrient that is just beginning to get its due” (3).
Some soil scientists are such new-found “aficionados” of adding calcium to soil that they recommend having it in there at a ratio of 65% (3). While this view is “to put it mildly, controversial” (3), it seems from some sources (17) and from Hemenway’s own experience (3) that adding calcium-rich materials can have a positive impact on soil, though it may not be necessary to inundate your garden with them.
Some holistic ways to add calcium to your soil can include adding specific calcium-rich plant materials such as Dynamic Accumulators like Dandelion (Taraxacum Officinale) and Comfrey (Symphytum Offcinale) (18) to your compost or sheet mulch, or planting them in your system so that they can help to make nutrients which are deep in the ground more available for nearby species. If you happen to be close to the sea, kelp and seaweed are also calcium-rich and can be added to compost or used as mulch (19).
At the heart of the matter
The final “major player” which Hemenway recommends for healthy soil is magnesium, which “is at the centre of the chlorophyll molecule” (3) so is “essential” for helping plants to process the nutrients they receive (3).
Most organic gardening websites seem to have only 3 sources for amending soil with magnesium: agricultural lime, magnesium sulphate (commonly marketed as Epsom salts) or dolomitic limestone (see for example 20, 21). If you happen to have lime in your system anyway, or if the bedrock in your area is limestone, then this is fairly easy to obtain. However, if you have limestone under the soil anyway the chances are that there is already enough magnesium present, and it is only if you are not near any limestone that you probably need to add it. Since the 3 mentioned are all mined products, the same ethical concerns as with rock phosphate apply to them. Magnesium sulphate is usually created by mining magnesite and then adding sulphuric acid (22). The magnesite mining process can be seen to have degrading environmental effects (23), and magnesite is not present everywhere so purchasing it may also include a lot of energy going into transporting it to where you are (see for example 22).
One more holistic way to add magnesium to your soil could be by adding nettles (Urtica Dioica) to your compost or sheet mulch (18). Kelp is also rich in magnesium as well as other minerals (19).
The last of the ‘big six’
Hemenway only names calcium and magnesium as the “secondary elements” although other sources also include sulphur as a third one (see for example 21). As with phosphorous and magnesium, the main recommendations for adding this element if your soil is deficient in it is to use it in its isolated, mine-produced version, elemental sulphur (21). I could not find any conclusive information on other more holistic sources. However, since a sulphur deficiency is equated with high-alkaline soil, it seems to make sense that any acidic organic materials could help to balance this. Acid soil is not generally desirable in a garden but some plants thrive on it, such as raspberries and blueberries (6). In ‘Gaia’s Garden’, Hemenway suggest some acid-loving guilds which could benefit from this (6). I have also had personal experience of working on a permaculture site where they mulched the raspberries with fresh eucalyptus leaves with the result that the plants produced more and bigger fruit; however, I cannot find any online evidence of others trying this. Perhaps the readers can help with this missing information.
Trace minerals and how to source them
Experienced permaculturalists may be already familiar with the above-mentioned elements and their integral roles in the creation of healthy, living soil. There is a lot of information out there about how to add these essential nutrients to your soil, and, importantly, there is probably always a source of them available to you which is cheap, energy-efficient and easy to access. What is perhaps less well-documented, and which has spawned all kinds of opinions and solutions, some not necessarily agreeing with each other, is the role of the “trace” elements of soil, the so-called “transition metals” (3). in the final part of this series I will explore, a little, the current research into how these minerals have been lost from soils and how to replenish them, and again look at the pros and cons of commercial sources of these elements and possible holistic alternatives.
1. Hemenway, T, 2016. ‘The Cosmos, The Earth and Your Health: The Story of Soil’. Toby Hemenway, 22/6/16. http://tobyhemenway.com/1363-cosmos-earth-stomach-story-soil/– retrieved 23/7/17
2. Hemenway, T, 2016. ‘A Big Bang for Big Soil’.Toby Hemenway,9/8/16. http://tobyhemenway.com/1388-big-bang-big-soil/ – retrieved 23/7/17
3. Hemenway, T, 2016. ‘Who Does What in the Soil’ Toby Hemenway, 29/8/16. http://tobyhemenway.com/1404-who-does-what-in-the-soil/ – retrieved 26/7/17
4. Ashwanden, C, 2017. ‘Gardening with wood chips: What, why, how and who?’ Permaculture News, 4/7/17. https://permaculturenews.org/2017/04/06/gardening-with-woodchips-what-why-how-and-who/ – retrieved 26/7/17
5. Long, T, 2017. ‘How to Chop and Drop More Effectively’. Permaculture News, 28/4/17. https://permaculturenews.org/2017/04/28/chop-drop-effectively/ – retrieved 26/7/17
6. Hemenway, Toby, 2009. Gaia’s Garden: A Guide to Home-Scale Permaculture. Chelsea Green Publishing, Vermont.
7. Haworth, C, 2014. ‘Building Up Soil for a Nutrient-Rich Raised Bed’. Permaculture News, 21/5/14. https://permaculturenews.org/2014/05/21/building-soil-nutrient-rich-raised-bed/ – retrieved 26/7/17
8. Barth, B, 2015. ‘Get a Load of Our Manure Guide’. Modern Farmer, 28/5/15. http://modernfarmer.com/2015/05/get-a-load-of-our-manure-guide/ – retrieved 26/7/17
9. Veganic Agriculture Network, 2017. ‘Fertilising with Human Urine’. http://www.goveganic.net/article217.html – retrieved 26/7/17
10. Steinfeld, C, 2007. Liquid Gold: The Lore and Logic of Using Urine to Grow Plants’. Ecowaters: New Bedford, USA.
11. Jasinski, S.M, 2013. ‘Mineral Resource of the Month: Phosphate Rock’. Earth Magazine, 2013. https://www.earthmagazine.org/article/mineral-resource-month-phosphate-rock – retrieved 26/7/17
12. Pearce, F, 2011. ‘Phosphate: A Critical Resource Misused and Now Running Low’. Yale 360, 7/7/11. http://e360.yale.edu/features/phosphate_a_critical_resource_misused_and_now_running_out – retrieved 26/7/17
13. European Parliament, 2015. ‘Question: Morocco’s phosphate mining in Western Sahara’. Europa, 19/3/15. http://www.europarl.europa.eu/sides/getDoc.do?pubRef=-//EP//TEXT+WQ+E-2015-004499+0+DOC+XML+V0//EN – retrieved 26/7/17
14. Engels, J, 2016. ‘How Plant-Based Permaculture is Possible’. Permaculture News, 28/10/16. https://permaculturenews.org/2016/10/28/plant-based-permaculture-possible/ – retrieved 18/6/17
15. Permaculture News, 2017. ‘Resources: Integrated Pest Management.’ Available as a PDF here: https://www.permaculturenews.org/resources_files/farmers_handbook/volume_2/9_ipm.pdf – retrieved 26/7/17
16. Shelle, 2017. ‘Testing your Soil pH without a kit’. Preparedness Mama, 2017. http://preparednessmama.com/testing-your-soil-ph-without-a-kit/ – retrieved 26/7/17
17. Soil Minerals, 2017. ‘Discover the Secrets of Soil Mineral Balance and Create Your Own Ideal Soil!’ http://soilminerals.com/ – retrieved 26/7/17
18. Temperate Climate Permaculture, 2012. ‘Dynamic Accumulators for emperate Climates’. http://tcpermaculture.blogspot.com/2012/01/dynamic-accumulators.html – retrieved 26/7/17
19. Hull,C, 2016. ‘6 Benefits of Using Seaweed in Your Garden: From Seaweed Fertiliser to Pest Control’. Organic Authority, 13/7/16. http://www.organicauthority.com/6-benefits-of-seaweed-fertilizer – retrieved 26/7/17
20. Hildreth, J, 1994. ‘Restoring Soil Nutrients’. Mother Earth News, June/July 1994. http://www.motherearthnews.com/organic-gardening/soil-nutrients-zmaz94jjzraw – retrieved 26/7/17
21. Corrigan, R, 2017. ‘How to Add Magnesium to Soil’. SF Gate, 2017. http://homeguides.sfgate.com/add-magnesium-soil-21551.html – retrieved 26/7/17
22. Chamotte, 2017. ‘Epsom Salts (Magnesium Sulphate Heptahydrate’. http://www.chamotte.co.za/index.php/products/magnesium-sulphate – retrieved 26/7/17
23. Zerman, R; Lorincz, A, 2006. ‘The effects of mining and processing of magnesite on the environment in SMZ JSC Jelšava’. Management of Environmental Quality: USA. Available as a PDF here: http://www.emeraldinsight.com/doi/abs/10.1108/14777830510623655 – retrieved 26/7/17