We do everything in our power to make sure the plants can grow as well as possible. We create an optimal lighting to make sure there’s a good supply of CO2. The third essential component is regular watering.
In its simplest form an irrigation system consists of a submersion pump coupled to a timer, to which hoses with drippers are attached. The submersion pump is placed in a vat of feed water with a volume big enough that we don’t have to fill it more than twice a week. A good rule of thumb is to use a feed water vat with a volume of at least 25 litres per m2 of garden space. Per square metre of garden this is 5-7 litres of water nutrients used per day. A top up once every 3 - 4 days should be enough. Keep in mind that there should be sufficient water in the vat to keep the heating element and the submersion pump under water. Both instruments will break if they run with no water over them...
The feedwater storage tank should be on the ground by preference. For a start, this saves space. It can easily be placed under the grow table(s). Secondly, this prevents that communication between vessels from occurring. If the tank is placed high up, the water will also flow from the tank without the need for a submersion pump. This will happen as long as the water level in the tank is the same level as the lowest point of the attached irrigation hose.
For the problem of communicating tanks there are solutions. For example, by attaching an electric tap between the feedwater tank and the irrigation hose. This solution is unnecessarily expensive. We can prevent the tanks from communicating by placing an overflow pipe at the highest point of the tylene (flexible pipe) and above the level of liquid.
The submersion pump needs to be powerful enough to drive water into all the attached sprinklers. For a garden of 2 to 10 m2 a submersion pump with a head of 7 metres when using a 1-inch irrigation hose is sufficient. The pressure of the submersion pump may also be not so high, since the sprinklers (also known as capillaries) don’t drip but spray...
Most sprinklers work with a minimum a pressure of 0.5 bar. We attach an irrigation hose (PE hose) to the submersion pump. This runs through the middle of the grow tubs. In the PE hose we make small holes, into which we fit the sprinklers. Install a sprinkler for every plant.
We want to avoid very narrow holes, which can block the sprinklers with dust and waste particles. We therefore do two things. First we close the feedwater vat with a lid, so that nothing unwanted ends up in the water. Secondly, we attach a filter (the so-called PE filter) between the submersion pump and the irrigation hose.
In an ideal situation the plants should have access to evenly sprayed water spread over the course of a day and receive nutrients. We can arrange this by using a timer clock on the irrigation system. A suitable timer must be equipped with a minute timer and be able to be switched on and off at least 6 times a day. Modern timers are digital; to save the entered time they use computer memory. In the event of a power loss they can switch to backup power to maintain their memory. In some cases the reserve power comes from batteries. This has the disadvantage that batteries can become depleted. If the batteries are empty and a power cut strikes, then the memory will be wiped. Then even irrigation stops and the garden can be damaged. It is therefore recommended that you use a timer with an accumulator as backup power supply.
Our irrigation system now ensures that the plants are given the right amount of food and water at the right time, and the sprinklers ensure an even spread of the feed water. The water can be drained away via a gutter (libra tubs).
The irrigation of the plants in an 18-hour light cycle is by preference split into 6 periods. The first feeding takes place when the light is switched on. Every 3 hours there is another feed, up until 3 hour before the light goes off again (the plants should be able to take up the nutrients during the light period, after all). In the beginning we let the sprinkler sessions last no more than a minute, or else there could be problems with the rooting. The short irrigation time is kept up for the entire veg phase.
In the generative phase (12 hour cycle), we further divide the 6 feeding events so that the plants are fed and watered every 2 hours. Because the plants by then have grown a bit, we let the sprinkler times last for 2 minutes.
When irrigating the plants you have to watch out that the feed water soaks through sufficiently. This is happening when around a third of the water given runs out again. This thorough soaking is necessary to make sure that nutrient salts do not accumulate in the rock wool mats. When you are not able to let sufficient water soak through, it is an idea to increase the number of sprinklings.
Everyone knows that water and electricity have about as good a relationship as water and fire. Both the submersion pump and the heating element work on mains electricity and under water. So only use materials that you are certain are well insulated. Furthermore, it is a good idea to remove all plugs from their sockets before you go sticking your hands into the water in the feed water vat. It can save you from a shocking experience.