After the flurry of activity last year to get the Dome built not much else happened on that plot because of the pressures of work and the weather and laziness. Now the weather is easing up a little it is time to start work getting the Dome plot productive.
There is a long list of things that need to be done but the main things are to get the perimeter fence built to keep out rabbits, level the ground inside and outside of the Dome, build the Aquaponics system, build the straw bail hotbeds in the Dome and insulate the northern side of the Dome.
Last weekend I started work on the Aquaponics system. We were given an IBC container but it is not ideal. I has a hole where we don’t need a hole and it used to contain styrene. It has been used for water storage for a long time so all traces of styrene have probably gone by now but I do not want to take any chances so I am going to line the IBC with a pond liner. I am building a simple IBC Aquaponics system for now but because I want to expand this later on into what’s called a CHIFT PIST system I have decided to bury the IBC in the ground. The topsoil at the allotment is quite shallow and then you get down to hard packed shale with lumps of granite so it was hard going to dig down the 700mm or so. The IBC is about a meter tall but I will be cutting the top off to form one of the grow beds plus I can remove the pallet from the bottom so I only have to go down the 700mm. I am undecided whether or not I need to insulate the fish tank from the earth or not. I think I probably will but we will see.
An IBC Aquaponics system is very simple and easy to build. It consists of a fish tank made from the bottom 800mm of an IBC container and a growbed from the top of the container flipped over. The water from the fish tank is continuously pumped up into the growbed at a steady rate which fills the bed up until it reaches the top of a siphoning stand pipe. The the water empties back into the fish tank and the whole cycle starts again. The growbed is filled with a growing medium like gravel or expanded clay pebbles and this is what your plants grow in. The growbed also has an overflow back into the fish tank just in case the siphon stops working and prevents the fish tank from being emptied which would be catastrophic for you fish. You can have problems with this system though because when the growbed or growbeds ar full there is little water in the fish tank and under certain circumstances the fish could get stressed due to lack of water. This is where the CHIFT PIST system comes in.
CHIFT PIST stands for Constant Height In Fish Tank, Pump In Sum Tank. The pump pumps the water from the sump tank into the growbeds which drain into the fish Tank which in turn overflows back into the sump tank. At all stages of the cycle the fish Tank is full so the fish never get stressed due to lack of water. Even if a pipe failed and all the water got pumped out of the sump tank the fish Tank would remain full. So this is why I am going to all the trouble of burying the IBC now. The aquaponics will be an ongoing project over the next few months but I needed to get the hole dug first. Here is the tank in the ground.
All the earth removed from the hole is going to be used to level and slightly raise the floor of the dome. We will then put down a layer of weed suppressant membrane and then cover with wood chips just so we have a tidy looking interior to the dome.
The next thing to go into the dome will be the straw bail hotbed. This will consist of a raised bed constructed out of 6 straw bails. The bed will be filled with fresh manure with a top dressing of compost. This will heat up and help heat the dome and will be a nice place to put our seed trays to help germination. In the summer we will plant melon and squash etc. Next winter we can then dig out the well rotted manure to use outside in the beds and replace it with fresh manure again to keep the dome heated over the winter. This is the plan anyway. As with everything I do in the garden it is a bit of an experiment.
We have done nothing to the outside area of the dome plot so that is also going to be addressed over the next few weeks. We are going to rip out the old fence and rotten posts and set scaffold boards on edge all around the perimeter. We will then build a framework of 2 by 1 timber with wire mesh attached to keep out the rabbits. The scaffold boards will serve a couple functions. One it will stop the wire mesh from tangling with the strimmers when they cut the grass between the plots and two it will mean we can fill the plot with manure and other organic matter making a large raised bed.
So we will be progress as we find the materials. We have the the weed suppressant membrane as a local company kindly donated a massive amount of sizeable offcuts. Certainly enough to do the whole dome floor. I need need about 7 scaffold boards to do the perimeter of the plot and I have 4 so far so that should not be a problem. I am still trying to find some straw bails and a supply of fresh manure but we will get there.