Heavy rains and drainage
I now live in Bundaberg, Queensland, the latitude is about 25 ° which is in the band of deserts around the world.
The winter climate is as near to perfect as you can get and is is possible to grow a wide range of plants. It rarely rains so as long as you have a supply of water everything is fine.
But summer is different, day after day we get these hot sunny winds with very high evaporation which just dries everything out.
If you are like me and have a thing about using chemicals the insects are a major challenge.
But we also get these summer cyclones which can drop massive amounts of rain causing major flooding.
I have found by bitter experience that if the roots of the plants are completely submerged for more than a few days they just die. However what I see is that if there are some roots which are not submerged the plant will survive. Maybe the deep roots will die but from what I can see the plants will soon regrow these lower roots without that much of a hiccup to growth.
I used to live in Melbourne and even there you can get major flooding, maybe not as regular as Bundaberg but they can still kill of any submerged plants.
Therefore my strong recommendation is that beds should be build so there is a layer of the soil above the surrounding soil, with no plastics or any waterproofing so that the water can escape quickly from that top layer.
I know the next question is how high should this layer be. There is a big difference in life between thinking you know something and knowing you know something. I have never been able to schedule cyclones to conduct scientific experiments so my answer is I think that at least 100mm above the surrounding soil is required.
That’s the way I make my beds, but we missed out on a decent cyclone this year so we will have to wait until the next cyclone to see if I think I know what I am talking about or actually know what I am talking about.
Top or bottom watering
The next question is about top or bottom watering.
If you had asked me last year I would have explained the positive benefit of bottom watering, particularly focusing on less surface evaporation and greater water efficiency.
However the Corona virus seems to have changed all the rules of life. Up here seeds are a bigger crisis than toilet paper and, I and everyone else, want to grow plants quickl with any old seeds we have left over. (New seeds are impossible to buy right now, I am scrounging of my mates).
I am a great enthusiast for baby greens and tipping where top watering is great.
That means that with bottom watering I would need to water everyday until the seeds germinated. And the truth is I am not a good routine person so I have converted most of my beds to top watering for now.
Nothing sophisticated, just a pipe with slots buried just below the surface. There are two points I would make.
It seems to be working fine – and being an engineer the first question I always ask is ‘does it work’ and tghe answer is yes.
The next point is it only takes seconds to unplug the top watering and reconnect to bottom watering, and engineers have learned that however good a design what really matters is can it be fixed when it goes wrong. (nb not if but when it goes wrong).
Soil dams
The next bunch of questions are about soil dams.
Let me try and explain what soil dams are all about. Many people make Wicking beds with stones in the base – which works fine if all you want to do is add nice clean water.
However things have moved on a bit and now we can use Gbiota beds (which are really just a version of Wicking beds with an external reservoir) to add nutrients. Again this did not cause any major problems.
But then we began to understand just how important our gut biology (and hence immune system) was for our health so people took a great deal of interest in spending large amounts of money on pre and probiotic pills.
Then some bright spark, (who is no longer employed and looking for a job) pointed out that these pills did not work very well and that the best pre and probiotics by far were natural plants which are full of biology and food – and were dead cheap.
That is when he lost his job as a research scientist.
But it did create a lot of interest in how to grow plants as natural pre and probiotics and so I began to think how I could modify Wicking beds to grow these plants pre and probiotics plants.
Anyone who reads any papers on soil and gut biology will quickly appreciate there are thousands of species with very long names so it all seems very complex and technical – until they learned the basic rules of biology which are – there are two sort of bugs, good bugs and bad bugs. If you feed the good bugs good bug food they will out compete the bad bugs.
So all we had to do was feed the good bugs, good bug food and they would win. Even better the food that good bugs like most of all (like cheese cake with me) is compost.
It is true that they do need minerals and nitrogen to help digest there favourite meal but as these come from rock dust (preferably volcanic) and animal manure which are both really cheap, in fact waste products so all was looking extremely rosy.
But then, as always happens with ideas that sound so great at first, the snags appeared. Specifically the combination of compost, animal manure (even if processed) and minerals was not only extremely potent food for the good bugs it would go putrid and stink to high heaven if left to stand for any length of time.
So that is when I came up with the idea of a soil dam, which in essence restricts the flow of water out of the base of the Wicking (Gbiota) bed so the beds floods then slowly allows the water to leak out to a sump ready to be recycled.
Now I am an innovator and have lots of ideas, most of them stupid and don’t work, but I have so say that the soil dam worked first time without any snags so I though there was no problems and everything in the world was wonderful.
All I had to do was jump up and down on the soil dam until I got the right resistance to give the right emptying time.
But it seemed that people just could not believe something so simple could work and I needed to make some instructions that people could follow.
Also I hit a problem when I made my dead simple Gbiota beds where I applied water from a hose rather than a nicely controlled low flow pump. I got a bit over excited and put the water on too fast ans washed my nice compacted soil dam away.
I solved that problem by using a bit of shade cloth I had kicking around to hold the soil in place.
So here is my recommendations.
If you are using an automated system with a pump and timer you will probably be pulsing the water after several hours (my time is set to three hours per pulse) so a drain time for the bed of around about an hour is fine. This is not precise but it does need to empty before the next pulse.
If you are like me getting infantile pleasure from doing silly things like squashing the soil with your bare feet then go for it. (I spend a lot of my life trying to follow the scientific method so a bit of a break and back to childhood is welcome).
If that is not your scene then make up bags of soil with some sort of porous cloth, (like shade cloth), to act as a restrictor.
You may need to do a bit of experimentation to find the right medium. Clay is almost certainly too resistant for an automated bed while gravel is to open. Fine sand tends to get washed away but a nice mix of sandy soil may be your solution.
But there is one little issue with the dead simple manual beds. Here you want a much longer emptying time as you don’t want to be watering the beds every day (once the seeds have germinated) so nice bag of clay may be the solution.
I spend my life experimenting (which I very much enjoy) but this is a job I am leaving to you guys hoping you will write in with your learning so I can publish or even better you can enter into the comments section.
Just a little tip. I am suggesting that you click all three buttons at the bottom of the comments section (or fill in the icon on the right) when you will receive notifications of new comments.
Also I am very happy to publish any articles you may write on my web (www.gbiota.com that’s my chatty web). There is some clever way that people can publish directly but I haven’t learned that trick yet.
As they say – we are all in this together.
Colin
ps have a look at my videos on YouTube, just search for Gbiota, I am making a new video every week to help people set up Gbiota beds to fight the virus