If Santa did not delivery you a pot, yard or field full of the ideal soil, don’t worry. Today we’re going to try to pull together what we learnt in the Second Episode (Part 1, 2 and 3) and what is available (in very general terms) to enable us to move towards the ‘perfect’ soil.
At the highest level, to resuscitate the soil we need to:
1. Consider our soil as a single, but large living organism and treat it as such.
2. Meet the needs of the organism which are much like any other living organism’s (including the human body’s):
- water, air, and an ongoing source of nutrition
- the building blocks / structure to house it in
- a stable balance of smaller creatures to fight disease, to aid nutrient digestion and to perform many other processes to maintain overall health.
3. Understanding these needs and an appreciate how the individual parts of the soil work together as a whole.
Do this, and we can kick-start a long-term, productive and self-sustaining garden on a healthy soil basis.
First we’ll do a quick recap to see where we want to be heading and why.
If you have recently read the Soil Series Part 2, then a lot of this middle section will be familiar with only a few new snippets which I have learnt (or been questioned on) along the way. If you skim down to the double line, you’ll hit the SOIL RESUSCITATION TRAINING COURSE.
As an introduction we learn that the physical nature of soil can be looked at as a pie diagram which includes (i) Mineral particles, (ii) Organic matter, and (iii) the Spaces in between. (Source)
MINERAL PARTICLES hold the MACRO- and MICRO-NUTRIENTS that dictate the plant’s capacity to thrive and reproduce. The spread sheet to your right is my conversion of information from (Life Sciences Vol I, Ahuja, M, 2006) into a table form (click on it to see it in a legible form), but is included to indicate the length of the list of nutrients required and the symptoms of problems, but also the inter-relationship of the nutrients/conditions to highlight that just adding one nutrient to fix a problem may be missing the true cause – presence of nutrient versus accessibility to plants….. NPK applied on its own isn’t ever going to provide a soil which will sustain itself and the plants from which we expect a yield.
It is important to note at this point that nutrients are typically brought to the plant as well as being made accessible to the plant via the ‘gut’ of soil life. A soil/bed producing the same crop year in and year out which is hungry for specific nutrients; where the crop is removed from the local ecosystem; and where no life support is applied to assist the nutrient replacement function of the soil biology, becomes depleted. Such farming/gardening is doomed to fail or become dependent on costly, continuous nutrient inputs.
An analogy of particle sizes is to think of rock melon, peas and poppy seeds… the balance we are looking for is between the pore space (i.e. water holding / drainage) and surface area (i.e. microbial living space).
If we think of an empty bath tub with the plug out. Now we fill it with rock melons. We have large particles (sand equivalent), large gaps between the particles and the surface area is limited by the skin on the number of rock melons we can fit in. If we turn the tap on, most of the water would flow straight through and only a small amount of water would remain predominantly that adhered to this limited surface (skin). With the run out of the water would go any nutrients held within the ‘rock melon’ pores, nutrients eroded from the rock melon surfaces or the hapless critter who fails to hang on tightly.
At the other extreme, if we filled the bath with poppy seeds, then we have tiny particles (clay equivalent), with tiny gaps and a huge surface area relative to that seen in the rock melon filled bath. If we turn the tap on, very little of the water would flow through (lets assume the poppy seeds wont head down the plug hole!) and a large amount of water would be retained. At spaces pore spaces <30 µm (note clay is <2µm diameter), the water / particle attraction forces are greater than the gravitational force acting to drain the water. The poppy seeds might also expand in the presence of water (much like clay) to further reduce the pore space. You end up with a waterlogged mess which will not allow air to ingress for respiration of the soil life….
However, if we have rock melons in the bath and then pour in peas to fill the rock melon space – let’s say we fill these spaces ~80% with peas. We have increased the surface area and reduced the pore space. Let’s now pour in poppy seeds to fill the pea space – let’s say we fill these spaces ~80% with poppy seeds. We have again increased the surface area and reduced the pore space, but not so far as <30µm (in an analogous sense!). This mix could be described as LOAM and is where we want to be!
A workshop query brought up the conundrum of why there was such a large section of the triangle labelled CLAY? After a little investigation the answer has been found to be that above a given percentage of clay, no mater what the other particles are like, the soil will act as clay and become easily water-logged. As the definitions describe the structure and hence an aspect of behaviour, there is no need for more than one broad category up at the clay end of the spectrum.
Like anything in life – in mineral particles we are looking for variety and all-in-moderation.
PORE SPACES are the gaps between all mineral and organic materials. As discussed above, the pore spaces also represent the pathways of water drainage and air flow, which in turn represents the major flow of soluble nutrients, and migration of bacteria, fungi, etc. These pores contain the critical elements for all life within the soil: Carbon (C), Hydrogen (H), Oxygen (O) – Present in combination as Air and Water. It is the edges of the mineral particles, general organic matter or the plant roots themselves (that border these gaps) where the fauna colonies thrive. Having said that, soil life not only depends on the pore spaces, but its larger members (worms, ants, nematodes etc) are responsible for the creation of them well below the reach of humans – unless we resort to tilling.
Whilst the PORE SPACES are influenced by the particle size, they prevalence is also reduced when the individual particles form clumps (or aggregates)…. known as the SOIL STRUCTURE. This can impact water drainage on a wider scale with granular and individual grains leading to rapid drainage, compare to the massive and platy (clay dehydration effect) aggregates.
Aggregates can be formed by:
- Soil microorganisms excretions – binding soil particles together.
- Fungi filaments (called hyphae) – tying particles together.
- Roots excrete sugars – help bind minerals.
- Electrostatic attraction between soil particles.
Again the soil life steps in to influence the soil’s behaviour.
ORGANIC MATTER is the final piece of pie and is defined as “matter composed of organic compounds that has come from the remains of organisms such as plants and animals and their waste products in the environment.” (Source) We are not talking about the certified kind of organic. “Soils are home to over one-fourth of all living species on earth, and one teaspoon of garden soil may contain thousands of species, millions of individuals, and a hundred metres of fungal networks.” (Source) These make up the organic matter section critical to the movement of nutrients as well as influencing the physical properties of our soil. However as teeming with life as good soil should be experience has shown that, with extensive human effort and some chemical based farming practices, it can also contain no life at all!
Recall the Soil Food Web – for dummies – could look like: (adapted from Picture Source).
Our friends the Chemical Engineers (making nutrients accessible to the plants and other animals), the Biological Regulators (the population controllers – consuming both flora and fauna) and, finally, the Ecosystem Engineers (they modify the soil structure reducing compaction and creating habitats) all operate far deeper than our trowel can reach if we provide the right conditions.
Another way to look at the food web is in a cyclical fashion, as mentioned previously, by following the individual nutrients through the web. Here is another huge topic, but at the highest level, let’s jump to my favourite topic as an example, which is carbon. The simplified path might look something like….
(Adapted from Picture Source; Elements of the Nature and Properties of Soils, Brady, N.C. and Weil, R.R., 2004; and the Soil Hugger herself!).
Speaking of my favourite topic carbon, ever wondered why no till farming is increasing becoming popular?
Assuming you’re not starting with completely dead soil (in which case rotary hoeing in amendments deep into the soil is likely a better starting point) or excessively compacted soil (in which rapid transformation is necessary – the fauna will get there, but will take time and encouragement! See below), then the negatives of tilling the earth are:
- Breaking the Fungi filaments (called hyphae) which:
- would otherwise hold the soil particles together in aggregates, which has the benefit of:
- allowing water to be held longer adjacent to roots.
- reducing the removal of nutrients as the bulk water drains through.
- reducing or eliminating erosion.
- deliver more distantly available nutrients to the plant roots in exchange for root exudates which it consumes as food. (Source)
- would otherwise hold the soil particles together in aggregates, which has the benefit of:
- Inverting the soil layers and hence changes the air ratio available deeper in the soil which:
- increases the short-term microbial activity increasing the rate of carbon breakdown and release it to the atmosphere. This carbon will take time to replace especially deep in the soil.
- effects the balance of fauna in the soil (microbes and hence higher forms of life are no longer at a steady state), reducing the soil’s ability to resist pests and disease.
- can cause exposure of deeper soil life to predators and unfavorable conditions (e.g. earth worms)
- The gardener has one more job!
- Tilling drags up the roots of annual or aged perennial crops leaves carbon (food) which would otherwise have remained deep in the soil keeping the fauna happy while the next plant grows.
- Tilling changes the pore spaces (some areas end up more compacted, other less) – pore spaces <30 µm, the water / particle attraction forces are greater than the gravitational force acting to drain the water.
- Tilling also breaks up the organic matter which has already fallen from the crop and would otherwise blanket the soil protecting it from the heat of the sun and the chill of frosts. Soil life is unhappiest under extremes of temperature.
From the diagram to your right you can see the difference between your average ‘undisturbed’ soil and the effect of compaction on relative proportions of the pie. Highly compacted soil shows less % organic matter which is due to the reduced particle surface space which is turn has resulted from the compression of the pore spaces. There may be a case for tilling in extreme examples, but give the organic matter time (and no pesticides to knock off the local life) and it will right itself – bring on the ecosystem engineers!
OTHER PROPERTIES – PH – You can add all the nutrients you like to the soil, but with an extreme pH the plants might not be able to access it. Bacteria like a neutral (7) pH and are depleted <5 or >9 pH, whilst Fungi prefer acidic (5) pH, but can exist between 2-7 pH. Organic matter mineralization is accelerated as a neutral pH is approached due to better microbial activity linked to happy bacteria. Hence the optimum pH is typically considered pH neutral (6.0-7.2). Having said that some plants love the more extreme pH and, if you’re struggling, this might be an avenue of investigation.
OTHER PROPERTIES – NATURE HERSELF
The evolution over time of plant systems shows the migration towards greater complexity and sophistication. This progression very commonly follows the sequence of cleared “barren” land” starting to grow weeds; then pasture plants or savannah grassland; followed by heath, shrub land; then open woodland of soft hardwoods (fast growing pioneer species); to a young semi-open forest; and finally to a mature closed canopy forest (climax). The mimicry and acceleration of this process is what we are aiming for when setting up a garden under the Principles of Permaculture.
The preparation of the soil to support such a system will require input initially (as we can’t wait the millions of years to replace the nutrients we have extracted, or go back millions of years to a different particle distribution!), but by focusing on how a forest operates – by harvesting sunlight; dropping leaves, branches and expired plants on the floor below; and providing habitats both above and below ground for the foraging fauna and layers of flora – we can facilitate the soils evolution in a direction we want and everybody wins.
So here we are, back up to speed and with the following information highlighted:
- most of the physical properties measure (or are worked upon to optimise) the aeration of the soil; the ability of water to infiltrate and to be held in the soil; and the nutrient availability within the root zone of the plants we wish to nurture.
- all the components must be present to hope for a self-perpetuating system.
- nature move towards the self-perpetuating system if given enough time.
Now we know where we want to get to. Namely:
- loamy soil;
- with lots of nutrients and a healthy soil food web (active organic content) to make those nutrients available;
- with medium density (not compacted); and
- covered to protect it from damaging forces (solar radiation, frost, larger order predators, compaction mechanisms…)
So how do we get there…… We apply a little TORK (or in Perth it could be considered to be CORK-ing the soil!)
T Texture – develop texture aspiring to loam
O Organics – Fine (compost) and Coarse (Mulch)
R Rock Dust – Long-term Macro- & Micro-Nutrients
K Kelp – Introduce Sea Minerals and growth tonics
As a pre-cursor, please note that I am not endorsing any product over any other within my comments. There are examples included so you can see what a specific product available local to me brings to our pure sand, but it is important that you chose locally available, ethical and economical substitutes to fulfill the same function. Do your research also about how much of the composition is providing benefit. Buying the expensive pure form and applying it yourself or buying the individual components and then applying the ratio you need may end up cheaper than diluted or general application products. Similarly course (less soluble) additions give the soil longer to ‘use’ them before they flush out of the soil with watering/rainfall.
- T Texture
We’ve talked about texture at length – in Perth sands this means we need to add C for clay (hence the CORK acronym works here). A jar shake test will let you know where you are relative to the oasis that is loam and hence what you need to apply to get there. Likely also silt.
We use West Australian pure calcium bentonite clay which is readily available, kaolinite clay is also available in bags, and there are many clays and clay blends which can meet your needs and often be sourced locally (dam walls etc). For poor sands (and with water restrictions!), clay should be mixed in deeply (25cm+) to maximise the water holding around the future roots – by hand or rotary hoe. For less dramatic application or where plants are already established, the clay can be applied to the soil surface before the mulch (or next application of mulch!) is applied and it will enter the soil gradually as you water.
The clay can normally be purchased in 20kg bags. The application rate will depend on the product, the state of your soil and the means with which you elect to apply it (dug in or superficial application). Thorough mixing of bentonite with sand/soil is necessary to avoid clumping in the short term (hence the rotary hoe).
- O Organics
Compost – fine organics – can be created in any number of ways which may be formal or informal, compost bins (in any incarnation), via chooks, worms or just as an aged form of coarse organics. Any organic waste removed from your property (kitchen scraps in the sulo bin, green waste collection, etc) is your system leaking nutrients. A fabulous person once said “There is no such thing as waste, only stuff in the wrong place.” (Thanks, Charlie – song, website) Feed you soil fauna and in turn your plants to support the next yield.
Mulch – coarse organics – Can be simply the act of dropping the prunings of your plant on the ground at its base and letting fallen leaves decompose where they lie. This effectively returns all the nutrients taken from the soil (to produce the leaf, limb or whole plant), back into the soil, as well as creating new habitats for your garden life. Alternately prunings etc can be left to dry out and then chipped for faster break down and a more conventionally neat look. However when you’re getting started and have not yet got green “waste” to work with, investing in some imported mulch (street tree, donated by a friend or other) might be the way to go.
The aim of the mulch is to mimic the debris which litters the floor of a forest. Covering soil is the number one goal for healthy soil especially in Perth over summer, when new plants might be fried. It is critical in the moderation of soil temperature, prevention of erosion and to minimise the moisture lost to evaporation (not only due to the sun’s heat, but the hot winds too). Whilst we talked about mulch above, this cover can also be provided by picking hardy ground covers to plant (sweet potato is a personal favourite!) as living mulch; ensuring larger plants protect it; or better still, all of the above.
The beauty of the organic component is this element can truly self sustain – build the soil and the life will come…bringing with them castings, manure, bodies and plant accessible nutrients. It’s uncanny how quickly life returns to barren ground once mulched.
The application rate would be classified as “more is better” especially with neutral pH mulch. With kitchen food scraps, other imported nutrient sources or compost products delivered to other parts of the garden, it is important to understand that, whilst the soil fauna might like it, some plants are built for limited nutrient situations (the pioneers) and some need to be spoon fed mass nutrients – over time you’ll figure out which is which. Too much nutrition and your pioneers are no longer required in the evolution of your food forest and will tend to fade…. a good thing…. they become terrific trellis’ for climbers and reflect that your system is working.
As an aside, for the plants that you intend to remove from your garden (no longer wanted or dead) always ensure that the roots are left insitu. This means that deep in the soil profile organic matter remains to sustain the soil life until the next plant’s roots dive as deep. This retention of roots acts to increase the depth of the living soil profile and increases your carbon sequestration (amount of carbon stored in the ground and hence less CO2 in the atmosphere! Win Win!) – but more on this in a separate blog!
- R Rock Dust (Long term / Slow release Macro- & Micro-Nutrients)
Contains: Nitrogen, Phosphorous, Potassium, Calcium, Carbon, Magnesium, Sulphur, Silicon, Iron, Copper, Zinc, Manganese, Boron, Cobalt, Molybdenum and Selenium in a balanced, slow release form. (The Green Life Soil Company) Some producers also bond it with beneficial microbes (bacteria & fungi -VA Mycorrhizae) to innoculate the soil and help establish healthy microbial populations. However unless you have organics in your soil to feed the microbes, they won’t stick around (or will just go dormant), but if you do have organic material available, and plants growing then chances are you’ve got your microbes working for you already.
There are lots of producers of Rock Dust in many different sized packages (small tubs to 20kg bags) but, as mentioned before use local ethical suppliers where possible and check out the product to ensure it meets the mineral needs across the board. It usually comes in a moistened form and is a mixture of granite and basalt rocks which has a significant spread of nutrients covered.
Typically its great to hoe this in at the start, but applied under the mulch is a valid option also. It is applied at 1-2 handfuls per square metre.
- K Kelp (Sea Minerals)
The application of sea minerals is a general boost to the fertility of the soil and hence the productivity of the plants. Information suggests that the application, due to the improvement in health, enables better heat, drought and frost tolerance as well as a better resistance to fungal attack and the impacts of insect attack. Generally it can be considered as a faster release provider of a broad range of trace elements and minerals.
In Perth we can purchase the coarse meal form of kelp, a fine powder (to be dissolved in solution) or liquid kelp already in solution with other additives. The only example of composition I have been able to find was for Seasol which represents an example of the latter. Again it is up to the buyer as to the volume and hence expense that is appropriate for them. We typically go for the coarse meal as we work in young sandy soils and don’t want it dissolving and flushed away before the soil wakes up. Horses for courses as they say. Again, choose locally available, ethical and economical option to fulfill this function to meet your soil’s needs. Anyway here is the example of Seasol’s contribution to your soil.
Application again will depend on your product, but typically the pure coarse kelp meal requires 1-2 handfuls per square metre and should be applied as per the rock dust. Work it into the soil mix or just get it under the mulch layer to start being eaten.
So there you have it. “TORK-ing to your soil” will provide you with the components you need to get started and bring in the little guys who make up the living bits of the organic piece-of-pie. They will do the rest.
Limited nutrition should need to be imported into the system down the track. This always worried me as I know my law of conservation of mass – matter cannot be created or destroyed – and my law of conservation of energy – energy can neither be created or destroyed. So if I take an apple off the tree and eat is (assuming I don’t have a black water system!) then I am removing a package of nutrients from the system and hence depleting it…..
But NO, this is not necessarily the case. When you acknowledge
(a) the free solar energy coming in and impacting on the most efficient solar panels in the world (leaves) as well as
(b) carbon and other bulk elements are freely available in the air.
(c) the mass transition of sub soil life and the nutrients which come and go with them,
you see that nature has this “progression towards self-sustaining” thing pretty wrapped up. It’s up to us to work with her to enable us, as part of the system, to obtain a yield without diverting her from her self-propagating course.
Wow…. got a little passionate there – back to topic SH.
Hopefully I have shown you how the complexity of soil can be simplified down to a focus on nutrient import, nutrient retaining and a whole lot of life thrown in. Confirming/adding Texture amendment, then throw in some Rock dust and Kelp with a topping of thick mulch to build your Organic content, and you are away.
Next time…..we might delve into one more Crazy Plant to help us inspire us to continue with the Permaculture Design series which we left hanging at the “client questionnaire”.
Until next time.