Water efficiency growing cannabis is one of the most asked questions we recieve from our customers, frequently worried about the huge water demands of plants, specially by those grown outdoors with bigger size. Water is a limited resource in our planet, so it is a good idea to try reducing wasted as much as possible.
Water consume growing marijuana
Marijuana plants need water for their developement, as any other plant. If we talk about water consumption of a cannabis plant it is good to specify that this consume depends on many factors:
- Size of a plant.
- Air temperature.
- Water temperature.
- Solar radiation.
- relative Humidity in air.
- Wind speed.
Logically the size of plant has a direct relationship with its needings (bigger the plant is, more water it will need to survive and develope properly). At the same time the sun plays a very important rol too. Plants put under high temperatures and powerful sun will tend to dehydrate quicker. So, we can affirm that those plants with a long sun journey will precise more water than those that only recieve few hours of light per day.
How to save water growing plants?
We know that water is an essential element for plants to survive, but if we talk about reducing consume we our plan is not to reduce the amount of water plants need, we just want to be more efficient using it so we don't waste a single drop of water. To do so one of the best ways to be more water efficient is to irrigate plants just before sunset, or early in the morning, when heat is lower, so the evaporation.
Water efficiency growing weed
As we said, there are many factors that we can not control, like size of the plants or day-light hours they recieve, but what we do can control is the use of the water to minimize (as much as we can) possible water losses.
Evaporation: Water evaporation happens when we water our plants in moments of the day when temperatures are too high (between 11am and 4pm), and the substrate is specially hot. If we like to avoid evaporation, a great solution is to water our plants early in the morning, or late in the evening (I specially like to do it at 8am or 8pm).
Another great solution, used by growers all-arround the world, specially in warm areas, is to cover the substrate with a layer that helps preventing against direct impact of sun to the substrate, so it works as a thermal insulation. Some farmers use special fabric to cover the substrate, but if we are growing in pots, it is better solution, and much esier, to cover the surface with perlite.
Pot material: Growing outdoors, specially in terraces, it is common to use plastic pots. Due to sun impact on them, this material gets hot, so it is not rare to see that mostly all growers use white pots as this color attracts less the sun than black or darker ones.. Even though water consume of plants grown in this containers is usually superior to others grown in other kind of container materials. As in this post we talk about water efficiency growing marijuana, and sustainability using water, we can not stop recommending to user other materials than plastic to be used for outdoor growing. Nowadays there are better insulated materials to use like porexpan or fabric pots. Using these kind of materials it is not rare to detect that the amount of water used to water plants will be less than using plastic ones, specially in terraces where the floor is hot and plants can consume up to 20% more water in adult individuals (about 1 liter a day per plant in a 40 liters pot).
Floor temperature: also growing in terraces, or in places where the floor is so hot due to sunrays, this may cause a dehydration of plants. Being the floor hot, this heat is transmited to the pot, that also will transmit it to humid substrate, what promotes evaporation (in this case we get a double harmful effect, because this heat will also "cook" our roots, what makes root weaker, causing plant illness). One good way of reducing dehydration of plants is placing the pots on insulating material (like porexpan used to protect some electronic devices). If we use these kind of insulating materials to place the pots on, it is not rare to beneffit from up to 20% of water consumation, reducing this way the total amount of water needed to water plants, so improving water efficiency.
Shadow covering: This option is so common in specially hot areas, with high intensity sunlight, and desert areas. Shading meshes, reduce sun impact on plants, what will help them resist against high temperatures thanks to solar retention that mesh resists. This is a light structure, resistant, an not too expensive, that can reduce the water evaporation up to 80%. It is important to mention that this is a good option to grow more discreet, because covering our plants will protect them to be seen from helicopters or high hills close to our garden. On the other hand, if we install this kind of meshes in areas were they are not strictly needed, it is normal to percieve a reduction of yields, dure to less sun intensity recieved by plants.
Products to save water
There are many studies that create a relationship between certain products use and water efficiency. Some of them had been used in areas were drought is a constant, to help plants resist better the periods of water shortage In other cases, where water isn't a problem, some products are used to get a more efficient consume of plants.
In-between these type of products we find humic acid or mycorrhizal fungi, that not only improve the hydric effiency of plants, they also add extra beneffits in growth.
As we previously commented, the use of shading screens, fabric pots or porexpan, can also minimize the hydric needings of plants without reducing the yields (and even improving in some cases).
Tips for a water effiincient irrigation
When we proceed to water cannabis plants, and how we do it is also a key factor when we look for a water efficiency growth. It is not logic to describe what's mentioned before in this post, and then use twice or three times the needed water to water your plants. In another post we talked about how to properly water your plants (we do recommend reading it), but today we will talk about when and how to water them.
When to water plants: All kinds of plants, and cannabis is not an exception, grown in soil, or coco, should be watered hydrating all the substrate, and then, once this is done, wait until the substrate is dry again. The substrate can take 24 hours, 2 days, 3 days, or even a week to dry, depending on their size, the size of the pot they are placed in, temperatures... The key point here is not how many days they need to dry the pot, but not to water them again until has dried.
How much water is needed: If we listen to other growers, or read some articles written on the net, is common to hear that we should water plants until we see the water is dropping through the bottom of the pot. It is true that this can be used as indicative, if we look for water efficiency (so we waste the minimum water amount possible) we should try to know the maximum amount of water the substrate can retain. That certain amount is something that depends on many factors, but we can know it just proceeding with low amounts of water, once and another, until we reach the total amount needed. Said this, it is important to mention that, specially for those less experienced growers, a spongy substrate can retain water easily, while dried substrate will drain the water quickly without retaining it. To help all those growers resolve that issue, the way to proceed is to water your plants with a very low quantity of water, then wait for about 5 minutes, re-water again with a low amount, wait for 5 minutes more, re-water again with low amount, and keep repeating this process until the substrate becomes spongy again.
Growing indoors (outdoors is not easy to use these type of systems) a great efficient formula to use water are hydroponic systems. Hydroponic gardens use a closed-system where water is in constant circultaion. As these systems use the same water for a week, or even more, there are no losses. These systems have other advantages that we will not detail here today, but that make them very interesting because of multiple aspects.
Aeroponic systems
* Growing in soil, or coco, using a flood irrigation method, is also a water efficient way to optimize thos parameter, due to plants uptake all the water used.
Water Filtering Systems
There are many water filter systems in market to purify water. These equipments use filters and membranes (used to make the water pass-through) that catch particules and salts dissolved in water, so they traansform tab water into RO (reverse osmosis) water with an EC=0. The use of these filters is a must for any grower looking for best quality and quantity (specially indoor growing), but it is also true that these type of filters waste part of the water used to produce a good quality water.
* We want to include this amendment because we think it is important to mention, in a post that talks about water efficiency, that not all the RO filters in market waste the same amount of water. At SantYerbasi we sell cheap RO filters that has a waste ratio of 4:1 84 liters wasted to produce 1 of good quality water), and also Growmax Water Reverse Osmosis filters with a ratio of 2:1 (2 liters wasted to produce 1 liter of RO water). We know that prices of these last ones is expensiver, but talking about water efficiency it would be a shame to use the cheap ones instead of more efficient ones. It is also important to mention that, wasting less amount of water will turn cheaper what we thought it was expensiver, because water is not cheap, so maybe in a year the extra money spent will be paid itself. In addition, these type of filters will also produce more liters of good quality water per hour, what makes growers a better life, so they don't need to wait long hours until they have the needed amount of RO water to water their plants.
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