How to stop wicking beds going stinky


Colin Austin © Creative commons, this article can be freely copied but please acknowledge the source and do not use for commercial purposes without author’s approval.


2nd Feb 2015

It will never work


Some twenty years ago - when I first started to develop wicking beds - the experts told me they would never work as they would turn putrid, stink and the plants would die.


Like most conventional wisdom they were right - well almost. It is absolutely true that if you have stagnant water with even a small amount of organic material, with no air it will go anaerobic and soon smell.


My challenge was to work out a way of stopping them going putrid.  My solution was based on my childhood experience of the flood and drain principle of lowering pots into a tank of water (actually compost tea). the water would expel all the air as could be seen by simply watching the bubbles.  You can see this in my video


However when the water drained out (or was sucked out by plants) as in the wicking bed fresh air would be sucked into the soil.


For this system to work you have to ensure that from time to time that you allow the plants to suck out all the free water.  Technically this is not difficult, and it works brilliantly.


I guess that some people are so mothering to their beds that they keep the water topped up all the time which resulted in the beds going putrid so somebody came up with an alternative solution of having stones covered with a cloth in the bottom of the bed.


Stones and cloth or soil biology


Up here is sunny Gin Gin we have tried both systems to see how they compare and the fact it they both work pretty well.  We have done this in glass boxes so we can watch what happens inside the bed.  It is clear that the cloth is no real barrier to the roots - they go right down into the water reservoir and suck out the water just like in the all soil bed.


So that raised the question which is the best system? 


One of our tests has been to compare the water holding capacity so various soils and the stone system.  The conclusion is that the system which preforms the worst is just to use heavy clay with no soil improvement, the stone and cloth system works better than the unimproved all clay mix however a good open soil outperforms the stone and cloth system.


A good soil simply holds more water than the stone system.


The improved soil mix has obvious advantages as the total amount of working soil is much greater and the nutrient content will be higher.


The obvious next question is how to get a good improved soil?


Improving soil


It’s now forty years since I ran a project on regenerating heavy clay soils - one of the most humiliating experiences of my life.


I tried all sort of chemical methods using any and every so called clay breaker I could lay my hands on - from gypsum, sulphur and all sorts of proprietary products. Basically none of them really worked - just minor improvements in some cases.


Then I tried a physical approach maxing up various mixtures, sand, stones, sawdust composts etc. Basically all I produced was reinforced clay which was harder and stronger than the basic clay - just as concrete is stronger than pure cement.


Next I tried mechanical systems of working the soil, using dry and wet soils and various methods of working from ploughing to rotary hoeing. Again while rotary hoeing dry soil produced a beautiful tilth as soon at first on the first real rain it just congealed into a solid mess.


Lesson - if you are in the innovation business learn to live with failure.


Soil biology


However I did learn that if you grow something (anything) and keep the soil moist that it will l convert into the most beautiful tilth with the very fine clay particles coagulating into tiny little balls.  I subsequently learned that this was the effect of soil biology - it is still amazing to me how soil biology can turn what is essentially a useless mass of clay into such a beautiful soil. I fear I may have become a soil biology nutter but the scientific evidence is clear - soil biology can dramatically change the structure of the soil and release nutrients so they are available to the plants.


If you think about it this is exactly what happens in the natural world.  Virtually all the energy that drives the world comes from the sun (apart from a minute amount of thermal energy). On land the solar energy is picked up plants and algae while in the vast oceans plankton and the sea plants do a similar job.  And all for free.


Plants break down carbon dioxide from the atmosphere and water from the soil in the process of photosynthesis to form a complex array of hydrocarbons which form the basics of life.


Trace minerals


But the chemistry of photosynthesis requires certain elements which come from rocks. But plants cannot absorb these elements from rocks. Plants can only extract these elements when they are chemically converted into solutions which are inevitably transient as they are soon washed away by rain.


However plants exude various sugars which provide the energy to power soil biology, particularly the fungi, which make these essential elements available to the plants as a form of slow release fertilisr.  It is an essential symbiotic relationship between plants and soil biology.


We should not ask which came first the chicken or the egg but which came first the soil biology or the plants.


Choices choices stone and cloth or improved soil


This does leave wicking bedders with a decision to take.  They can use the stones and cloth approach, buy potting mix (which is typically inert), a range of chemical fertilizers and any sprays needed to keep the pests and weeds under control and grow plants which are nice and neat and tidy and look good.  There is no doubt this works.


The alternative is to go for a soil biology approach which will produce plants with a greater range of nutrients and healthy phytochemicals and learn to live with the implications. Soil biology is a complex business and we simply do not have the technology to be able to cultivate only the beneficial biology.


The only approach currently available to us is to create an ecosystem which favours the beneficial biology which can then provide some degree of control over the harmful biology. For example we know that certain fungi will control the nematodes which attack the root structure of plants.


When I studied organic farming in America some time ago they had a system of sterilising the soil with methyl bromide - which kills everything - then introducing the known beneficial species. I am not sure what the current status is as Governments around the world are trying to ban methyl bromide which is a highly toxic material which destroys the ozone layer. 


To my way of thinking this misses the key point that we simply do not understand the thousands of species which make an active soil biology so introducing isolated species inevitably means missing some species which may well be critical.


The situation seems totally analogous to taking vitamins pills versus eating plants rich in phytonutrients.


Managing imperfect knowledge


Soil chemistry, particularly the surface chemistry of the particles, has a major influence on the soil structure as it can make the fine particles coagulate into a porous matrix.

Science gives us a very clear understanding of the mineral required by plants particularly the process of photosynthesis and the key elements needed,

A simple run through a spectrograph will show the type and quantity of the elements in a plant.  We can also undertake tests in which growing plants are deprived of certain minerals and see if they are healthy and if not then adding that mineral and if the plant recovers then it is proven that that is an essential element. On this basis we can say we have a good understanding of the elements needed for plants to grow.

With humans it is a bit more difficult, there is a shortage of willing volunteers who are prepared to be deprived of key ingredients in their diet to see if they die or hopefully almost die, then see if they recover if they are then given the chemical under investigation.

That process was used unintentionally by the British Navy to discover vitamin C and the study of various remote tribes has helped us identify further vitamins, but the fact remains that there are probably many critical food components which we have yet to identify – in fact we are still discovering new vitamins at a reasonable rate.

What is very clear is that the human body needs many more elements than do plants, some like selenium and vanadium etc. plants do not seem to need at all while others like magnesium and zinc are required by us in much higher quantities than plants - see (Newsletters particularly Newsletter_22_June_2014.pdf).

Phytonutrients, health and partial understanding


But plants provide a crucial role in making these minerals available to us in a form in which they can be processed by our bodies.  There are literally thousands of phytochemicals produced by plants which we regularly digest and we have yet to understand the role they play in our health.


My aim in my experiments with soils has been more than learning how to grow healthy plants but growing plants that will make us healthy.  It is clear that the synergistic relationship between plants, soil biology and the minerals in the soil play a crucial role in this.


As humans we have to accept that we have only partial knowledge of what forms a healthy diet.  You only have to search the internet to see the range of views and diets being promoted by reputable scientists (let alone the quacks and conmen).


How do we manage our lack of total understanding?  Do we just confine ourselves to foods which contain compounds which science has proven is beneficial or do we aim for a diet which contain the full range of phytonutrients which have evolved over time even though the scientific proof of their benefits has yet to be established?


This is question which has to be based on judgement.  My view is that the wisest approach is to focus on developing the soil biology to create a healthy soil and once you have a biology active quality soil then using the cloth and stones approach is as the jargonist like to say sub-optimal.  This is my philosophy in developing Wickimix™ which is discussed in


Colin Austin