How to Regulate Automatic Irrigation

25-05-2016 - Grow with Mr. José

When growing most plants, how they are watered is absolutely crucial and is often the deciding factor in whether the crop will be successful or, on the contrary, unsuccessful. Many growers try to automate irrigation, either to save time or for more efficient cultivation. To this end, there are a variety of automatic irrigation systems you can use, but most of them will not guarantee the correct level of moisture in the growing medium. Let’s have a look at how we can best regulate automatic irrigation.

Before you start to set up the irrigation system you must be aware of what is needed by the plants you intend to grow. You should also ask yourself whether you are going to focus mainly on setting up automatic irrigation for a greenhouse or for plants under artificial light. For cultivation with sunlight you have to consider natural irrigation when it rains and greater fluctuations in temperature – optimal irrigation settings are not possible without additional automatic regulators and sensors, which we won’t discuss here. Let’s go back to the needs of the plants. Most plants cultivated for their fruit or flowers need regular watering and enough oxygen at their roots. This means that you need to alternate high and low humidity in the growing medium. When you water a plant, it always absorbs dissolved nutrients from the water. As the growing medium dries out, the roots have enough of the all-important oxygen. If the growing medium is permanently wet, the roots will begin to rot and the plant will die. Maybe you will now object that there are cultivation systems in which the roots are permanently under water, even if they are not aquatic plants, and this is true. However, don’t forget that the water in such systems must be constantly oxygenated to guarantee the optimal mix of moisture and oxygen. You certainly know that, if you don’t water plants at all, they will most likely wither. Every species of plant has specific requirements for the level of moisture in the growing medium. For example, pepper plants like high humidity levels, but bulbous plants are less demanding. Hemp is able to absorb a large quantity of moisture. The bigger the plants, the greater the consumption of water.

Moisture and the Growing Medium

The moisture in the growing medium and an appraisal of whether the plant is being watered enough greatly depend on which growing medium you are using. The frequency of watering is also governed by the current size of the plants and by climactic conditions: atmospheric humidity and temperature. These are all elements which must always be taken into consideration when setting up automatic irrigation. The very best way to determine the optimal dose and frequency of watering is to do it manually for a while. In this way you can best identify how much water the plants consume. When watering manually you can try to observe exactly how much water or nutrient solution you are using, and how frequently you need to administer it. If, for example, you establish that a plant consumes 500ml of water per day, you can try to set the irrigation so that this plant receives exactly that amount. And how do you know that a plant needs to be watered when watering manually? For specific growing media, as follows:

Soil Substrate

If you have a light and nicely aerated substrate, it should permanently be slightly moist. You can increase the aeration of the substrate by adding perlite. As water usually soaks down to the bottom of the planter, it’s better to check the moisture level by stabbing your finger through a hole in the bottom. As a general rule, if some water comes out with your finger, there is plenty of water in the substrate. When growing in flowerpots, you can also identify the amount of water in the substrate by weighing the flowerpot. Compare the weight of the plant before and after watering. In this way you will more easily identify whether or not the plant has already consumed all the fluid before you water it again.

Coco Coir

Again, you can check the moisture levels of this medium by stabbing a finger into it, or by weighing the flowerpots, if used. It is very easy to overfill coco coir when watering, so I recommend mixing coco coir with perlite 50-50. This will greatly increase the permeability of the coco coir fibres and will create the ideal conditions for the growth of the root system. Coco coir can also be mixed with peat or with heavier types of substrate, because they lighten it slightly. You can mix it with rockwool and ex-clay too – or both in the case of hydroponic cultivation systems.

Rockwool XE "Rockwool"

Rockwool is primarily used for hydroponic cultivation. If it is too dry, it absorbs water very poorly. If there is insufficient moisture, the plants will very quickly indicate this and will start to wilt. Rockwool is very porous and overfilling it is very easy, so water carefully, particularly at the beginning, when the root system is developing. Too much nutrient fluid can easily be identified. Make a small hole (1-2 cm) in the mineral wool with your finger. If it fills up with water, the moisture levels in the rockwool are too high. We can now proceed to cultivation in mapito, which is similar to rockwool.

Ex-clay XE "Keramzit" (expanded clay)

This growing medium, which is in itself intended exclusively for hydroponic cultivation, is very difficult to overfill. You will recognise the correct moisture levels by stabbing your finger into the grower full of ex-clay (from above and below). You must be able to feel the moisture. If the plants are still small and there is only a small probability that the roots already reach into every part of the grower, stab your finger in as near to the stem as possible, but be careful not to damage the roots. You can also weigh the growers when using ex-clay.

Now you know how to identify the correct moisture levels in the growing medium. It is very important to check this before you water the plants. If you stick to this approach and learn how to water plants manually, it will be a significant help when setting up automatic irrigation in any cultivation system.

The Primary Settings for Automatic Irrigation

Let’s assume that you have already chosen an irrigation system. The most common is probably drip and pressure irrigation, which can be installed basically anywhere and with minimal costs. When selecting one of these systems, don’t forget about filtering the irrigation solution, whether it is pure water or water with nutrients. The system is suitable for connection before planting, at least if you are doing it for the very first time. In this way you can check that the irrigation is working without difficulties and the solution is not leaking anywhere it is not needed. Also you can find out how much solution flows from the irrigation unit for one plant during a specific period of time. If you have capillary irrigation and one capillary leads to each plant, you can find out how much solution flows through this capillary during 30 or 60 seconds. When everything has been measured and everything is working, you can use the automatic irrigation system for real. Before you bring the automatic timer into play, you should turn on the irrigation manually for a few days. At the same time, remember that the growing medium must provide the plants with moisture and oxygen. It will never hurt to oxygenate the water or nutrient fluid with an aquarium compressor (especially in hydroponic systems). It has also been shown that frequent irrigation with smaller doses of solution is more effective than one larger dose. If, for example, you know that one plant needs 500ml of water or nutrient fluid per day, it is better to give it five doses of 100ml than two of 250ml. You should also try to distribute the watering evenly throughout the day. This means that, if you are watering five times daily, you should carry out the first one in the early morning, the last in the evening and the remaining three at equal intervals during the day.

Subsequent Setting of the Irrigation System

Whether you are growing in substrate or hydroponically, you must react to the plants’ changing requirements during cultivation. The volume and frequency of watering sufficient for a 10cm-high plant is probably not going to suit a 1m-high plant. Therefore, it is necessary to make regular checks on the moisture levels in the growing medium, and always before watering. Usually it is necessary to increase the frequency and volume of watering, but you should always do this gradually and increase the doses slightly. After changing the intervals and duration of irrigation, you should check the moisture levels in substrate just before the next watering cycle.

Mistakes in Irrigation

Faulty irrigation is the most common cause of poor harvests, stunted plants and a number of diseases or other problems. Overwatering is far and away the most common problem. Many people think that the growing medium must be permanently wet, so they water the plants so often that not enough oxygen can reach the roots, and as a result the roots quickly start to rot and cannot deliver water and nutrients to the parts of the plant above the ground. The plant will react to this by starting to wither. A lot of growers interpret this symptom as the result of insufficient watering, so they start to water the plants even more, which is exactly the opposite of what the plants want. This approach means that the plants will stop developing, they will continue to wither, and if the situation is left unchecked, they will die. It could be said that if you had to choose between underwatering and overwatering, you would create fewer problems by underwatering. But of course your goal is optimal watering; that is why you have learned manual watering before setting up an automatic irrigation system – to understand the plants better.

Worry-Free Automatic Irrigation

If you are just starting to grow hemp and you don’t have the time or the inclination to bother with setting up an irrigation system, there remains one other possibility – buy a ready-made system which will be very tolerant towards any mistakes on the part of the grower. In this instance I would recommend two systems. One of them is Aqua-System – a hydroponic system which can irrigate non-stop and which will always guarantee the correct levels of watering. This system needs a little electricity to run, but not enough to stagger you! Generally, it can be said that a hydroponic system with ex-clay as the sole growing medium is highly unlikely to overflow. Another suitable system is AutoPot – a passive growing system which does not need any electricity and which in addition will water each plant separately and exactly in accordance with what it needs. Another advantage is that there is nothing to be set up; you can grow organically, both hydroponically and in substrate. Of course you will have to pay extra for any system that will tolerate your mistakes – nothing is free! Automatic irrigation will give you more freedom, and in addition it will always water the plants at the same time. Plants like regularity. There is only one condition: the irrigation must be correctly set up. You know how to do that now.

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