Questions and Answers

 Hello Colin,

We need to recycle our grey water which  we can not obviously presently use on our vegetables at present.  Do you have adaption's we can make or another system we can use so that we can recycle grey water, last year we received 540mls of rain this year it is down to 111 and as we rely on our tanks (no mains water where we live) it is critical we find a way to use every last drop or we have to start carting in water.

The fruit trees are already planted and we definitely could not uproot them again  they would simply die.

Cheers Hayley


Hi Haley,

I suggest you have a look at safeguarding_future_food_supply.pdf  this shows how I used open style wicking beds to irrigate an established orchard


Hi Colin
Great website. I am making a shadehouse with three beds this weekend.
Quick question if you have time- what stops the organic matrix water reservoir decomposing over time and causing the soil bed to sag. How do I stop this ? Is it just a case of digging up sections over time and adding organic waste to the matrix?
Thanks for a fine website !

 Hi Damian

I actually want the organic material to decompose, this is continuously adding nutrients to the soil  (and is also sequestering carbon) so you do need to top up with more organic material.


There are two ways.  Dig out a section of the bed  ( I go down to the top of the pipe so I dont not puncture the plastic) then refill with organic material.  I then spread the excavated soil over the bed until it is flat.   I just use a new spot for the hole each time.


That is the hard work way.


The second way is to make a compost heap on top of the bed and water the compost.  This flushes a nutritious compost tea into the base of the bed.  This is the lazy way.


In fact I use a combination of both methods. When I weed my bed I just throw them onto the compost zone and let them decompose.  After a while I am accumulating a pile of composted material which I then bury.


Now there is one important point.  Composting takes a lot of nitrogen so it is a good idea to add some nitrogen fertilizer to the compost.  I use blood and bone and chicken manure.



Hi Colin 

Great website.

I am also interested to know what is best for the organic matrix. Some
websites say woodchips pull too much nitrogen out of the soil bed. I was
thinking of using a bagasse, woodchip and mulch mix. Maybe you already
answer this question (I need to check your Q&A section). Also, some sites
say use hay or straw or lucerne bales in the organic matrix but other sites
say this introduces all sorts of weeds and pests into the garden beds.

Thanks for the reply.


 Hi Damian

Weeds and pest are a real problem up here in Queensland.  I have never found that simple composting kills of seeds, although some people claim that a hot compost will.  The way I have found that is 100% sure is to immerse the seeds in water.  Seeds are very difficult to kill so I like to let them germinate in the compost then bury in the bottom of the bed where they are immersed in water and a long way from the light.  Once germinated the young plants are easily killed.



Hi Colin
Im about 2 years into a project using your wicking worms beds in containers until our next house where I will put in a more permanent arrangement. On the Costa Garden Odyssey show  I saw that Costa used a geofabric between the soil and the water storage area (sand in his case). Do you know what geofabric he used or at least its specification?. I would guess that it would have to allow the wicking but to keep the soil from the water area in order to allow better flow?
Im starting to get blocked water drains (soil and roots) in some of my containers and so Im thinking about a rebuild using the geofabric with the original design.
Thanks for everything, as a technology I think it is terrific and Im spruiking it to all my friends and pointing them to your website
Peter Hayward

 Hi peter

Now there is a real issue here.  Most people are familiar with the conventional wicking system which has a separate water container with the water wicking up into the growing area.


I have googled wicking bed patents and there are hundreds of different versions of this principle.  But they all have the disadvantage that they need a separate container which is fine for a pot or tub but is totally impractical for a large area.  In my system there is no barrier between the water and soil zone, the water is simply stored in the soil or organic material.


Normally the water available to the plants is the difference between the field capacity (the maximum water that the soil can hold by capillary action) and the wilt point.  Typically this is only 10% of the soil contains available water.


In my system I increase the water holding capacity from the saturation point to the wilt point which means that the available water is increased several times, particularly if a coarse organic matrix is used.  While the volume of water contained per unit of volume is obviously less that in a water container with liquid water the total volume of water stored can much larger than any practical container.  This makes it practical for large area farming.


I am currently experimenting with a system where rows of wicking beds are all linked together by a system with many beds running along a contour but all linked together by lateral running down any slope.  This can be used for large areas.


I do have patents on this system but I actually encourage home growers to use the system for free as this helps promote the system.


Another of my current projects is to get the system accredited for carbon capture.  At some point when carbon trading becomes a reality this will allow growers to earn money from carbon capture.



Hi Colin
Ive been using the EarthBox system to great success but Im very excited by your wicking bed system as it integrates the water and worms into a complete system and so Im keep to start converting to it.  I have one simple (hopefully) question for you. I see the need for the use of a ShadeHouse to keep pest and birds out from enjoying the rewards of your system. I am wondering about how pollination is handled if a shadehouse is employed? Im not a very experienced vegetable grower but I wouldve thought that the vegetables that flower would be compromised by a shadehouse inclusion.
Peter Hayward

 Hi Peter

I know that commercial growers using hot houses will pollinate either by hand or by having a bee hive in the house.  Living up in Queensland with an abundance of insects I have never found pollination to be a problem



Hi Colin

I'm building my first wicking worm beds this weekend and had a quick question.

I've got 2 choices of readily available (free) material for my organic matrix / reservoir layer and was wondering which would be better:
1) Street mulch (fresh mulch from tree loppers - could be anything - probably gums)
2) Composted sheep manure (well composted from my brother-in-law's farm).

Would either of these work?
Would either of these be better?

Thanks for your helpful website,





Hi Hendy,


The tree mulch from the loppers is the best for the reservoir however there is a few things to watch for.  Some trees, particularly pine trees put out toxins or inhibitors to stop other plants growing in their area and competing.  Trees may look pretty but they invented chemical warfare.


It is therefore best to allow a bit of time for the loppings to weather and let the microbes dispose of the toxins.  As long as you keep them moist then a month or so should do.  If after you have made the bed you think the plant growth is not what is should be then you can always give the bed a good flush.


Next as organic waste decomposes they take up nutrients, particularly nitrogen.  I therefore suggest that you mix the sheep manure in with the soil in the root zone.


Hi Colin,


I have made my bed to the dimensions you suggest but in the winter I notice that the surface is still wet.  Am I putting on too much water.






Hi Jeff,


Yes probably, the surface should look dry for most of the time.  If it is wet it can encourage moulds on your plants.  In winter there is no need to fill the reservoir up to the drain hole, you can experiment with filling to a lower level until the soil surface is dry.


Also do not water too often, make sure the water in the lower zone is all used up, at least from time to time.  There is still plenty of water in the soil.





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