The irrigation system
We do everything we can to promote plant growth. We provide optimal lighting and sufficient CO2. As a third component, regular irrigation is an essential link. This way the plants receive their water and nutrients in time. The easiest way is to water by hand several times a day. But, in the first place, that involves carrying a lot of watering cans around, in which you’ve dissolved the correct amount of fertilizer every time. In the second place, watering by hand requires enormous discipline. Giving water regularly on time will quickly ‘water’ YOU down You can’t skip a few days here and there, and leave your plants to themselves. Finding a babysitter for cannabis plants is often more difficult than finding a babysitter for your kids . . . So, we prefer to give water regularly with an irrigation system controlled by a timer clock. This way, we can rest assured the plants get their wet and dry periods on time. In Chapter 3, we’ve given a lot of attention to the installation of an irrigation system. Now, we’ll go a little deeper. In its simplest form, an irrigation system consists of an immersible pump, controlled by a timer clock, which has hoses with sprinklers attached to it. The sump pump is placed in a nutrient tank with a capacity large enough to make refilling necessary only two times per week. We’re talking about a tank with a contents of at least 25 liters per square meter of garden space. 5 to 7 liters of water with nutrients are used every day for each square meter. So, refilling the tank every 3 or 4 days is enough. Remember, there must always be enough water in the tank to cover the heating element and the pump. Both instruments will be ruined if they are left without water Preferably, the nutrient tank should sit on the floor. There are two important reasons for this. In the first place, it saves space. The tank can also be underneath the tables. In the second place, it prevents the natural working regarding water levels between communicating vessels. If the nutrient tank is placed too high, the water will flow through the hose without the aid of a pump. This goes on until the water level in the tank reaches the same level as the lowest point of the connected irrigation hose. Solutions can be devised for the problem of ‘communicating’ vessels; – coupling an electric faucet between the nutrient tank and the irrigation hose, for example. This solution is unnecessarily expensive. The problem of communicating vessels can be prevented by placing a sprinkler outlet on the top of the hose. The sump pump must be powerful enough to send water to all the sprinklers that will be installed. For a garden 2 to 10 m2 in size an immersible pump with performance capability of 7 meters is enough, if used with a 1-inch irrigation hose. Also, the pressure of the pump should not be too high, otherwise the sprinklers (also called capillaries) won’t drip, but spray Most sprinklers function at a pressure from 0.5 bar on up. To the immersible pump, we connect an irrigation hose (polyethylene or PE- hose). The irrigation hose goes through the middle of the grow trays. Then we make holes in the polyethylene hose and insert the sprinklers. We install one sprinkler for every plant. We have to prevent dirt and other materials from clogging up the narrow openings of the sprinklers. We take two measures: first, we keep a lid on the nutrient tank so nothing undesirable falls in the water. Second, we place a filter between the pump and the irrigation hose. In an ideal situation, plants should get water and nutrients spread evenly throughout the day. We can arrange for this by connecting a timer clock to the irrigation system. A suitable timer clock must also have a minute setting, and must be able to switch on and off at least 6 times a day. Modern timer clocks are digital. These clocks have a memory to store the desired times. If the electricity goes off, batteries usually supply current to preserve the memory. The disadvantage is that batteries run down. If the battery is dead, and the electricity goes off, the memory is erased. The steady watering stops, and the garden is damaged. The recommended choice is a timer clock with a good car battery for backup. Now, our irrigation system ensures that the plants get the correct amount of water and fertilizer on time. The sprinklers evenly distribute the nutrient solution. We prefer growing in ‘libra trays’; – so-called ‘growing trays’ which have been especially designed for growing on rockwool slabs. There are other methods, of course. You can also lay rockwool slabs on corrugated roofing sheets, for example. This does give problems with drainage water . It’s more hygienic, and more practical to work with growing trays. They’re not expensive, and it’s simple to connect a drainage system to them. Easier still is snapping drainage spouts onto the growing trays. Then the water can be drained into a gutter. We divide the irrigation of the plants into 6 periods during the 18-hour light cycle. The first feeding takes place when the lights are switched on. A feeding session follows every 3 hours, until 3 hours before the lights go off again (the plants can take in nutrients only during the light period!). In the beginning, we don’t let the irrigations periods last more than one minute, because otherwise, problems with root development can occur. We stick to short feeding periods. Throughout the entire vegetative phase. During the generative phase (12-hour light cycle), we also divide the 6 feeding sessions so the plants will get water every two hours. Since the plants have grown a little by then, and they need more water, we let the irrigation periods last for two minutes. When irrigating the plants, you must make sure the nutrient solutions soaks through thoroughly. Thorough watering means that about one-third of the water applied drains off. Thorough watering is important to prevent the accumulation of the nutrient salts in the rockwool slabs. If watering is not sufficiently thorough, it’s sensible to raise the number of irrigation sessions. Finally, another word about safety. Everyone knows that water and electricity are equally related as water and fire. The sump pump, as well as the thermostatic heating element, work with use electric currency and under water. Use only equipment of which you are sure it is well-insulated. Moreover, it’s sensible to disconnect the plugs before you put your hands in the nutrient tank. This can save you from a possibly shocking experience.