How to water marijuana plants in soil

Which is the best way to water marijuana plants in soil?

Novice growers often ask themselves which is the best method for watering their cannabis crops in soil. While it is true that marijuana needs a lot of water, it is also true that it does not tolerate over watering, so it is easy to make mistakes. By following these tips you will ensure optimum results from your crops.

Cannabis is a plant that does not like continuous irrigation. It is imperative to water abundantly our crop and then wait until the substrate gets dry to water again, either with fertilizers or with tap water.

Follow these rules to calculate the needed amount of water per plant:

The volume of water needed in each irrigation must be, at least,  a quarter the total volume of the pot or container.

Examples:

For a 1L pot, use 0.25L of water in each irrigation
For a 4L pot, use 1L of water in each irrigation
For a 12L pot, use 3L of water in each irrigation
For a 30L pot, use 7.5L of water in each irrigation

Usually, we will have to water 2 or 3 times, slowly and uniformly over the surface, to properly moisten all the substrate. Place pot plates under the pots so they will be filled with water once we irrigate the plants; this water will be absorved by capilarity in less than one day. It is also very important to use a quality substrate not only with good retention capacity but also with good drainage (our substrate should contain clay pebbles, perlite and/or coco coir,...)

Once watered, you can notice that your pots/containers are now very heavy, being difficult to move them. What you should do now is weighing the containers every day - you can do it with your hands -. You can use a pot filled up with dry substrate to compare both weights. Once they have lost most of their weight, it is time to water them again.

In effect, as water weighs much more than soil, a pot saturated with water weighs a lot more than another ready to be watered. With a little practice, you will quickly learn when is the appropriate time for watering your crops.

This technique is extremely easy and efficient, and suitable for any kind of potted plants! Using this method, you will probably water your plants every 3-6 days. Several factors may require a more frequent irrigation, such as small pots, dry and hot climate, sun exposure,etc.

Drip irrigation does not offer good results in soil, and it should be only used in exceptional cases (holidays). If you want a functional drip irrigation system, you should forget about soil and use any hydroponic substrate available on the market (coco coir, rockwool, clay pebbles, etc).

 Which is the best water to irrigate marijuana?

You can use tap water as long as its EC value is <0.4. Otherwise, you should dilute it with pure water (EC = 0.0) such as rainwater, or osmosis/demineralized water in order to get an EC value of about 0.3

Indeed, cannabis plants don't like chlorine, limy (hard) water or other substances contained in tap water. It is recommended to allow your water to evaporate all chlorine (rest for 24hrs) at room temperature.

• Osmosis water is perfect for cannabis growing as long as we add a few supplements. It can be easily found in pet/fish shops, or can be produced by using an osmosis system. We should add Calcium/Magnesium/Trace elements since most fertilizers are made for using with tap water.

• Rainwwater is also very useful, but it is recommended - specially indoors - to put it in the microwave for a few seconds to sterilize it from bacteria, eggs, fungi spores, etc.

• The water pH value must be between 6 and 7. Otherwise, it should be adjusted with a pH tester and a pH reducer.

Marijuana watering tips

During the last weeks before harvest, the plant's need for water descreases. We must then progressively reduce the amount of water in each irrigation, because we can have problems with molds developing in the buds if the substrate takes too long to dry.  Furthermore, a slight "water stress" at the end of flowering increases resin production.

However, don't forget to flush your plants with water (without any fertilizer) 3-4 weeks before harvest.

Use fertilizers every 2 irrigations, or two times out of three. Flushing your plants with water (eventually, you can add enzymes or humic/fulvic acids) dilutes and "recycles" those nutrients accumulated in the soil, which can cause an intoxication of marijuana plants .

After a few irrigations, a hard layer may appear in the surface of the substrate. Break it gently and regularly so water can moisten the substrate correctly. You can use natural humectants with your irrigation water to avoid this issue (Yuca, Aloe Vera…), which also allows better water absorption and nutrient assimilation.

Naturally, the bigger the plant, the more water it needs. If you notice that a specific plant needs less water than the others, you can reduce the amount of water per irrigation so you can water all your plants the same day. The same happens with plants that demand more water than the others.

Spraying the plants with water makes the plant to develop less roots, so you shoul avoid spraying them more than 1-2 times per week. Since plants get water from their leafs, they don't develop a nice rootball to find it in the soil.

The first symptoms of over watering are similar to drought. Weigh your pots to know what happens: if the pot weighs too much, you are over watering your plants!

Happy irrigations and harvests!!