World Water Day is observed each year on March 22nd to promote the responsible use and access to safe and fresh water for everyone. This year is about accelerating change and what we, as a global community, can do to help solve the world’s water and sanitation crisis by encouraging people to change how they use, consume and manage water. 

Why is this so important?  

According to the 2023 United Nations World Water Development Report, 26% of the world's population doesn't have access to safe drinking water and 46% lack access to basic sanitation. 

In the United States alone, the agriculture industry accounts for roughly 80% of the United States consumptive water use, which is the amount of water removed from available supplies without return to a water resource system. 

At Grodan, our goal has been and always will be to provide growers with the best products, technology and services. By utilizing our Precision Growing principles, we aim to support cultivators, regardless of their experience and the size of their operation, to reach the goal of producing more with less, from seed through harvest.  

Our stone wool, more than almost any other growing media on the market, has one of the highest water-holding capacities due to the unique composition of the rock fibres. With more water readily available for uptake by the plants compared to other mediums, like coco or peat, for instance, it can be challenging for some to avoid overwatering, especially when it comes to our smaller starter cubes and blocks.  

How to avoid overwatering during propagation

The more water you apply or, the deeper you submerge the cubes, the more air you push out of the substrate. This excess water will only slow down root development and weaken the plant making them more susceptible to diseases. 

For the first irrigation, after dry back, the water only needs to touch the bottom of the cubes or go up to a quarter of an inch up the side if using a flood or dip method of irrigating. If top watering, a quick gentle spray or mist will help re-saturate the medium and refresh the substrate without drowning out the young developing root zone. Some cultivators, at this time, may opt to grade their cuttings by separating the ones with roots showing from those that aren’t in an effort to prevent overwatering.  

When it comes time for the first irrigation, growers should measure the tray or cube before and after irrigation and then record the weights and experiment with the saturation levels to find what works best based on the specific variety being propagated. 

The importance of an irrigation strategy 

Finding the desired balance between vegetative and generative growth requires a smart cannabis irrigation strategy, one that’s been tailored to a cultivar’s unique genetics and growth habits, as well as their goals for the final product and how the root zone was established and managed during previous growth stages.  

As previously mentioned, only by monitoring and measuring the weight of a Gro-Block regularly and throughout the irrigation process can cultivators determine the exact timing and allotment of daily water needed. By utilizing this method, growers will have an easier time understanding the substrate’s water retention and drainage cadence. 

How much water should you give the plant during each watering event? 

The volume of each irrigation event should be equal to 3% to 6% volume of the stone wool you are watering. It’s also important to remember that when stacking a block on a slab (or another block), you need to add the volumes together to determine the proper irrigation volume. 

For more information on irrigation events and shot sizes, download our wetting instructions for Grodan Improved Gro-Blocks below. 

To find out how you can “Be the change” in your community, explore issues, and see how others are making a difference, visit www.worldwaterday.org/learn.