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Automatic Watering for your Cannabis Grow

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In this article we’re going to talk about how to set up automatic watering for your cannabis grow, something that can genuinely be a lifesaver for growers that have spent years hand-watering their plants.

Technically, 100% automatic watering is something that still can’t be done, but there are systems in which, if you pick the right substrate, you can water a large amount of plants by simple keeping a tank full of water. This can be helpful if you’re growing a rather large amount of plants so that you don’t have to spend hours watering them all.

If you decide to use this method, keep in mind that your plants won’t grow the same than if you were to hand water them and mind them one by one – if you have lots and lots of plants, then doing this is probably not in your best interest. You can also do this if you don’t have time to water your plants and you only have a few in your grow tent, but keep in mind that the yield will be a bit lower.

If growing in soil you should only begin watering automatically when you’re sure that your plants are drinking a reasonable amount of water per day. In my opinion, I think automatic watering in soil should be used no earlier than when flowering begins, and in a 7L pot your plants should be drinking about half a liter of water a day.

You need to program the watering so that when it waters, it only gives your plants the amount of water they need for one day – you can’t water a 10cm plant with two whole liters as you’d end up soaking the soil, the roots will rot and you’ll probably end up with a dead or hardly productive plant.

If you want this to be more efficient, then you should grow in coco coir which dries up faster than soil, or in coco coir or rockwool slabs. These kinds of substrates drain the leftover water efficiently, so even if you manage to over-water your plants they should dry up soon enough and your roots won’t rot. This means that you’ll be able to water much more efficiently in this medium. Once your plants are big they can dry out our pots or slabs two or three times a day, needing to be watered more than once but this can easily be controlled with a digital timer.

If you’re growing in soil it can be hard to get the timing right, and if you mess it up twice in a row your plants will suffer quite a lot, which is why we recommend using a different kind of substrate with better water drainage if you want to use this automatic system.

Automatic watering is as easy as having at least a 2L tank per plant. You can even prepare enough water for a week, so the most you need to use is 1.5L per plant for 7 days – this is perfect as a week is about how long mineral nutrients can last in water without going bad – if you use organic nutrients you might end up blocking the pipes and you’ll also need to mix them every day as they won’t last more than 24h in the water without going bad.

You need to place a submergible pump into your tank which is capable of maintaining pressure in the pipes, so that the same amount of water comes out of each micro-pipe so that, logically, the plants all receive the same amount of water. You’ll need to install a pipe system that then connects to micro-pipes used for drip irrigation – make holes in the main pipe system for each of your micro-pipes which will then be used to water your plants. You can get pipes that can deal with 16 of these micro-pipes, or drippers such as the Octopussy, which has 6 micro-tubes etc.

Now you need a growing table so that the water can drain out under the flowerpots and flow into a tank which you can then empty – never reuse water from these kinds of systems, and always ensure that your timing is right so that you don’t waste precious water and nutrients, as you’ll basically be throwing money down the drain.

You should have your system set up by now, but you still need to know how much water is being pumped per minute by the pump. Place a glass at the end of one of the drippers and turn the pump on for one minute with the timer to see how much water your plants will be getting per minute. Once you know that, you’ll know how long you’ll need to have it on for when watering. Generally, half a liter per minute is what most pumps give – if you get more than that then your pump is much too big – you need about 1000L/H per square meter of grow with 16 plants in each square meter for the micro-pipes to work correctly.

The last thing you need to do is get an air pump with an air stone, which will ensure that the nutrient mixture and the water is in constant movement and oxygenized – your fertilizers won’t end up accumulating on the bottom and will always be available for your plants once the pump turns on.

Each time you need to fill the tank up again pay attention to how your plants react; if they’re soaked, if they’re too dry, anything that could indicate you need to change your method or water them more/less. They should grow massively and if you’re using slabs they can grow so big that you’ll have to water them up to 3 times a day.

Automatic Watering for your Cannabis Grow – Material needed

Flood table:
These are trays that have grooves in them so that you can direct any leftover water to a specific point, where you can then channel it through a pipe to wherever you’d like or simply leave a tank underneath the hole on the tray itself so that the water can fall down into it. These trays are easy to clean once the grow is done and they’re very efficient when it comes to getting rid of water so that there’s never any leftover water sitting at the bottom of your pots and soaking into the soil. They’re also useful in the fact that leftover water from one plant has the opportunity to be absorbed by another plant, which can help avoid all sorts of salt excess in the substrate and whatnot. There are various sizes available to fit your exact needs.

Water tank:
There are all sorts of water tanks out there that you can use, although we recommend using one that has a lid if you’re growing with chemical or mineral nutrients, as they’ll last the full week and the water will be better conserved if it has a lid – there’s also less possibility of getting fungi infestations and algae that tend to occur when light hits the water- You can also use one of the square tanks without a lid and place it right under the table or inside a grow tent, which can save a lot of space. You need to pick the type of tank but you also need to pick the capacity – the most you’ll use per day is about 2L per plant once they’re fully grown and drinking the most they’re going to drink, so calculate that into about a week of growing and get the right sized tank.

Water pump:
You’ll need a submergible water pump that can give out about 1000L/H per square meter of grow, which is about 16 plants. With this pump you can rest assured that you won’t be pumping too much water per minute, so there’s no need to worry about accidentally over-watering your plants. The minimum amount of time you can program is one minute, and make sure that in that minute no more than half a liter is being pumped out. You need to clean your water pump for every new grow to make sure that it keeps working perfectly – if you wait too long to clean it, it might get all blocked up and break due to the salts used in the water. Make sure to buy a quality pump, and not the first one that you see, as your entire grow will depend on this pump working properly.

Watering pipe:
This tube is used placed in a straight line between two rows of flowerpots or slabs, and the micro-pipes are used alongside the sides of the main pipe – the main pipe is in the middle and then the plants are to the right and left of the pipe, kind of like a corridor. You’ll need one line of pipe per two rows of plants and then you need to place the micro-pipes – there are various models, some of them just need one hole in the main pipe and have 6 different drip pipe endings, some have 12, and some require one hole in the main pipe per drip pipe. You’ll need to pay close attention to the pipes in case they accidentally end up blocked – if you use Ata Clean in your grow about once a week then you can forget about worrying about blockages in the micro-pipes.

Rockwool or coco coir slabs:
Slabs are growing systems that are similar to hydroponics, where the growing medium is wet and then dried often, so it needs continuous watering, and these substrates hardly retain nutrients so you need to add nutrients in almost every watering. You’ll need to plce five slabs on your flood table, cut an X shape in them and place clones in the hole, from 3 to 5 should fit. Place a drip pipe at each plant and all you need to do is pay attention to when it dries up to know how often you’re going to need to water per day.

Air pump:
Air pumps are used to give the water in your tanks more oxygen as well as keeping the nutrients in constant movement, which is something that your plants will greatly enjoy. You’ll need to place an air stone so the oxygen particles are smaller and easier to mix up with the water.

With all of these objects you can easily set up automatic watering for your plants, a small comfort especially if you have a large amount of plants. Don’t forget to keep everything nice and clean so the micro-pipes don’t end up blocked, no algae grows in the tank and no rot begins appearing in the water. Happy growing!

Author: Javier Chinesta
Translation: Ciara Murphy

Automatic Watering for your Cannabis Grow – Learn how to set up automatic watering for your coco coir or rockwool slabs with this informative article.

Automatic Irrigation for Cannabis

Growing cannabis with automatic irrigation

Cultivating cannabis is an art in which each grower uses their best techniques and their own knowledge, as well as different growing apparatus that can help to manage the growing environment or as in this case, the automatic irrigation of cannabis plants.

Automatic irrigation in cannabis cultivation

The duration of a cannabis crop is around 3 months, with the first month for the plants vegetative growth and at least the next 2 months for flowering. During this time plants require water and fertilisers every few days, so irrigation will become a repetitive task that can end up tiring all but the most dedicated grower, especially when time is at a premium.

Manual or automatic irrigation in cannabis cultivation

Pretty much every grower starting out in cannabis cultivation will usually irrigate by hand, but how can we simplify this task?

Many growers prefer to water by hand and can be a bit reluctant to adopt automatic irrigation systems, but when you use one for the first time there’s no turning back. Automatic irrigation gives us more free time to check the plants or to dedicate to other tasks.

Automatic irrigation can be as simple or as complex as we like, depending on the requirements of each grower and the aspects that they want to control, such as the pH or EC. Watering each plant with the same amount of water, using short waterings will mean that the plants will feed well while maintaining a high degree of oxygenation in the roots and preventing the plants from the extremes of drying out or being flooded with water.

Let’s see how automatic irrigation can work with cannabis:

Drip irrigation in cannabis cultivation

Automatic drip irrigation is the simplest and most useful method, as well as the easiest to control, because apart from being able to assemble it to fit according to necessity, there’s also the possibility of being able to use adjustable drippers for when certain plants drink less than others.

SOG with 36 plants per m2 and drip irrigation system

The versatility of this type of irrigation

is what makes it an option well worth considering. There is a wide range of products that can be adapted to the needs of each grower, factors such as; number of plants, cultivable m2, vertical wall irrigation, amount of irrigation per minute, adjustable flow, etc.

Let’s see an example:

In this case, a SOG grow has been carried out, in which 36 plants per m2 have been cultivated in a mounted irrigation system using the following components:

1- Irrigation tube 16mm
2- Elbow connectors 16mm
3- End caps 16mm
4- T connectors 16mm
5- Hose 16mm
6- Water pump 700l/h

7- Drippers 40ml/min
8- Digital timer programmable minute by minute
9- Nutrient tank 90L
10- Grow tray with drainage
11- Air pump with diffusor stone

In the photo you can see an even growth over all the plants by having a balanced diet and accurate watering during the vegetative stage. In this case, there was an initial watering of 30 to 40 seconds, started manually, and later automated using a digital timer, in order to regulate the amount of water and nutrients as much as possible.

SOG with 36 plantas per m2 with drip irrigation

The root development of these plants is explosive and their growth is vigorous since the beginning. This vigor is due to a degree of humidity and stable dryness of the substrate during the vegetation phase. In this case trichodermas have been used to have a greater and faster colonisation of the root zone, in addition to improving the ion exchange between substrate and root for better assimilation of nutrients by cannabis plants.

In this setup, the irrigation water has been drained away, meaning it is not recovered and reused once it has left the nutrient tank. Coco fibre, clay balls, rockwool and in general all hydroponic substrates can be used in recirculation, but it is preferable to drain the solution to avoid altering the nutrient solution in the tank, in particular with coco fibre, rockwool and soil .

If we recirculate in rockwool or clay pebbles, when we water, the runoff that escapes from the drainage holes at the base of the pot can dissolve salts deposited on the pot or grow tray. If these salts are washed back to the deposit they can raise the EC and disrupt the pH levels.

Flushing the roots with automatic irrigation

The same thing applies to soil or coco, it’s better to irrigate to drain than to recover the runoff, as the salts could upset the stability of the nutrient solution in the deposit, which will later affect the plants. Moreover, small particles of substrate can clog the water pump or the irrigation tubes.

Setting up an automatic irrigation system

To begin to assemble the automatic irrigation, we need to be clear about the space that the crop will occupy and the number of plants to be cultivated, to help us estimate the size of pump needed, the quantity of drippers and the layout of the main and secondary branches of the irrigation pipes, as well as and where to make the joints with the elbows and T- connectors.

We’re going to use a common case as an example, in which 16 plants per m2 are in 7L pots with soil as the substrate. What materials are required and how is the space arranged for the irrigation inside a 1.20m2 closet?

First of all we have the 1.20m x 1.20m grow tent with a 1.20m2 cultivation tray and 16 plants and a 90L tank, which can be left outside or placed inside the tent underneath the tray. If there’s enough space, and to facilitate filling the tank, it’s better to leave it outside of the grow tent, if there isn’t enough space in the room, we can fit it inside the tent.

Now that the tray and the tank are in place, we can look at the distribution of the pots and a sketch of how the irrigation system should be set up. In this case we already mentioned that we will have 16 plants per m2 and the most logical way to fit all 16 plants in is to use 4 rows of 4 plants each.

Layout sketch of an irrigation system for 16 indoor plants

Layout sketch of automatic irrigation for 16 plants

In this example, as we can see in the sketch, there are 16 pots, with 4 rows of 4 pots. What we will do is use a main line and two secondary lines to feed the drippers, which will be anchored in the cultivation pots. Let’s see how to assemble the irrigation system step by step.

The main line: This is an irrigation pipe, in this case 16mm, which is attached to the pump located inside the tank. To connect the main line to the pump a piece of hose of 16mm (same size as the irrigation pipe) and a connection T has been used to connect the right and left sides of the main line and. The main line runs, in this case, horizontally so that the secondary branches go vertically.

Secondary lines: These are irrigation pipes, also 16mm, branches connected to the main, horizontal line. The number of secondary branches depends on the number of pots and how they are distributed in the grow space. In this case, only two secondary lines are required, which each feed two rows of pots, a total of 8 pots per secondary line. To connect the secondary branch to the main line, we can use elbows or T connectors, in this case we need 2 16mm elbow connectors.

End cap: The final stopper as its name indicates is a cap that is fitted, normally, at the end of the secondary branches to avoid water leaks and to create the water pressure that allows it to exit through the microtubing and dripper stakes.

Water pump: In this case 700l/h is enough to feed the 16 pots of the grow. When selecting an irrigation pump, apart from the flow rate in litres per hour, it is necessary to take lift into account, which is the amount that the pump has to move the water vertically. If we have are growing at at ground level there is no problem but if it is more than 1 meter high we have to look for a pump that has a lift strength of 1.5m. The pump attaches to the hose to be push the water through the drippers.

Microtubing and drippers or stakes: The part that connects the secondary branches with the plants. The microtube allows a restricted water passage of between 40 to 60ml per minute to perfectly control irrigation. The drippers or stakes are attached to the microtubing, by means of an internal thread that connects them, and are driven into the substrate in the pot to allow the water to reach the plant.

Digital timer in minutes: A digital timer that allows us to control irrigation with a minimum time of 1 minute and a maximum of 24 hours. This timer is responsible for starting and stopping the irrigation pump automatically, according to the users settings.

Air pump and stone diffuser: An air pump that takes air from the room and pushes it through a non-toxic silicone tubes to the stone diffuser. The diffusing stone is responsible for spreading the air in small bubbles inside the nutrient deposit, and keeping the nutrient solution oxygenated and in good condition.

Water heater: a simple water heater allows you to maintain an optimal temperature for the nutrient solution, around 20ºC.

Nutrient tank: It is a water tank in which the mixture of nutrients is made to be able to irrigate by automatic irrigation.

Giving your automatic irrigation system the professional touch:

There are many other grow devices that can make a conventional irrigation much more professional. It’s possible to further automate the irrigation and to make it more complex, which consequently allows better management of the irrigation and the dosing of fertilisers, greatly improving the final result. In this case we’re talking about pH and EC Pumps.

How to use a pH pump

A pH pump is a cultivation tool that allows us to automatically control the pH of the nutrient tank for maximum convenience. The pump consists of a probe that is continuously reading the pH of the nutrient solution and depending on the resets assigned by the user, the pump will raise or lower pH levels as required.

Kontrol01 pH Pump

As we can see in the photo of the Kontrol 01 pump, it is a square unit, containing the mechanism in charge of slowly and gradually pumping pH down acid (mixed with water) to the nutrient tank via a non-toxic silicone tube. The pump works by taking water with a very low pH from a bottle, or another tank, which it then pumps to the nutrient tank, where the pH is high.

The pump relies on readings given by a probe to monitor the pH level of the nutrient solution in the tank. The unit activates automatically and will continue pumping until it has lowered the pH to the level indicated by the user.

There are two types of pH pumps: one that incorporates a probe within the pump itself, independently monitoring the pH in the tank; and the second type, that need to be connected to a continuous PH meter as in the case of the Milwaukee MC720 pH controller with pump. If we already have a continuous pH meter, we need only buy the pump, which is always a little cheaper than the other available option, as in the case of the Kontrol01 pH pump.

Milwaukee MC720 pH Pump Controller

When growing in soil, normal pH is between 6 and 7. If the pH must be lowered, we can use an acidic liquid, such as PH Down from GHE or Citric Acid from Trabe to lower the pH in the tank. The same thing applies when growing in coconut, clay balls, rock wool, aeroponics, or in DWC.

Tips and tricks when using a pH pump

When using a pH meter that continuously monitors the levels, the pH readings are always active so if levels get high enough, the pump will keep adding acid to raise the tank to the correct level. As we are dealing with irrigation to drain, rather than recirculating, we can avoid the pump working all day and continually wasting pH down in the solution by setting the unit to only regulate the pH for a few minutes before the irrigation pump is turned on to feed the plants.

To perform this task, we need only add a timer switch to the pH pump programmed to turn on 15 minutes before the irrigation pump does and to deactivate just before watering.

An example of this method would be, if we water once a day at 15:30, we set the timer so that it will activate the pump from 15:15 to 15:30. During this time the pH pump works to stabilise the pH at the indicated level and then switches off. This operation is automated throughout the grow, removing the need to regulate the pH every time we water.

It should be noted that in hydroponic systems such as coco fibre, where a large number of short irrigations are used per day, this is a very good option to have the pH always under control, resulting in a heavier, higher quality harvest thanks to the high stability of the pH from the start to the finish of the grow.

EC Control Pumps to stabilise nutrient levels

También existen bombas controladras de EC que hacen la misma función mantener una Ec estable durante todo el cultivo, ideal para los sistemas de recirculación donde la misma solución nutriente realiza una y otra vez el mismo circuito alimentando las plantas diariamente.

En el circuito cerrado las plantas se alimentan de la Ec del depósito de modo que la EC del mismo se va reduciendo a medida que las plantas se van alimentando. Es en estos casos donde también es imprescindible el control de la Ec.

There are also EC control pumps that do the same function to maintain a stable EC throughout the grow, ideal for recirculation systems where the same nutrient solution makes the same circuit again and again feeding the plants daily.

In a closed circuit, the plants feed on the nutrients in the tank, meaning that the EC levels are gradually reduced as the plants are fed. It’s in these cases that controlling the EC is essential.

We hope this article encourages you to set up your automatic irrigation system, you’ll only have to work a few hours to save lots of time in the future and get better results! Do not hesitate to leave here your doubts and comments, we’ll be pleased to reply them.

In this Alchimia blog post we take an in-depth look at automatic irrigation systems, outlining the advantages of automated watering, detailing how to