Cannabis garden substrates like soil, coco and stone wool all have different benefits for the Cannabis garden and play a part in our recipe for crop steering. Each has their own moisture gradient from the top to the bottom. Understanding these differences and subtleties can increase your yields and health of your plants. Stone wool has become a preferred choice for myself and many indoor growers to help create uniformity of canopy growth. Whenever considering new substrate products, you want to choose one that drains according to your desired feeding schedule. Additionally, some substrates can hold more water than others. Stone wool substrates aim to make it easy to replace nutrients inside and gain better control of the plants. Cultivators steer crop growth on the basis of climate and irrigation strategy, which is largely determined by the choice of Stone Wool blocks we use.
For my home garden, Grodan offers an ideal range of stone wool blocks that produce uniform quality plants with excellent yields. Companies like Perlite Institute and The Schundler Company produce perlite and vermiculite, which are commonly used as components in growing media. Vermiculite is excellent for water retention which means water that it holds has more nutrient retention. Perlite is great for drainage and is commonly made from heated volcanic glass. It's so lightweight, doesn't decompose and is great for aerating compact soils. For indoor home medicinal plants and commercial facilities, I prefer a stone wool substrate for ease-of-use, lower environmental impact and overall cleanliness. Many hydroponic retailers have their own brands of media to choose from.
ParGro by Grodan is the standard stone wool substrate that was used before Grodan released their newer Improved Gro line. ParGro is still cost-effective for many applications and I still use it in my home garden. It doesn't retain as much water, and it drains faster, making it great for smaller facilities and projects. It has a slightly slower refreshment rate than some others and is available in all the most popular configurations.
"We're striving to create a Stone Wool substrate that's more adaptable to crop steering and various environments." Says Ben from Grodan during our discussion.
When we're looking at crops, we're aiming for maximum outputs with minimal inputs, considering labor, materials, nutrients, and water. It's an integrated approach involving energy and labor. Precision is key to maintaining the right moisture level; too much or too little can lead to issues. Managing the substrate is easier than soil or cocoa, offering an environmentally sound growing method and improved business performance.
Two common parameters of control are the root zone environment and canopy environment, involving water and air content in the root zone, electrical conductivity, pH levels, and temperature. In the canopy environment, we deal with air movement, temperature, relative humidity, radiation, CO2, and pressure levels on a seasonal and daily basis. Effective Root Zone Management is ongoing to ensure optimal crop growth and production.
When you master Root Zone Management, you'll typically see increased yields through controlled growth and steering. This results in improved product quality and batch consistency, allowing you to replicate success consistently. Ensuring uniformity in the substrate, considering water distribution and volume based on growth stage, is crucial.
Grodan 3-phase feeding drain system focuses on re-saturation, refreshment, and direct drain. The choice of when and how much to irrigate depends on whether you want a vegetative or generative response in your crop. EC levels play a crucial role in controlling the plant growth, with lower EC allowing for more water uptake.
Three Phase Feedings & Drain Charts
Phase one is your first shot of the day at your peak water content in the substrate. One of the major pitfalls I see cultivators experience during feedings is draining before they reach desired water content. They start pushing more water thinking they can pump their shot size but they're actually dumping water on the table, exactly opposite of what we want. They should be having multiple small shots in that first phase to build up the moisture content when they reach the second phase. That's when you start draining to the desired water content. Draining allows for refreshment in the core of the subject. In phase three, that is a good trigger for the plant to be regenerative or vegetative with response to your last shot of the day.
You can have large dry backs overnight to be generative or the reverse for vegetative steering. Whenever you lose too much moisture in the third phase of the day, you have to restore it in the first phase. If you don't replace enough moisture in the first phase of the day, then the next day you have to trend downward, which might be good for a generative response in the crop but if you're flowering for two months it can get pretty stressful for the plant on this day-to-day 24-hour water cycle.
How does Electrical Conductivity (EC) affect plant responses?
If you're increasing the EC in the substrate or the dripper you're going to have a generative response. If you're decreasing EC, you're going to get a vegetative response.
If you're steering in these directions, think of it as a scale. You have multiple types of triggers throughout the day and you might have a couple vegetative responses to tip the scale one way and then one big generative variation in the third phase of the day. So when you're steering it becomes a balancing act between these indicators. Balancing your salts with your clean water flushes will help increase these responses towards how you want to steer the crop.
The other thing is people get comfortable taking drain readings out of the bottom of the substrate. The water that comes out of the substrate is not necessarily indicative of what's going on inside. So cultivators put a 2.0 shot in there, plus salts, and I see them get scared because they take a drain reading and then see it's 0.5. They change the irrigation practices prematurely and then they're chasing their tail. But if they wait until it begins to drain and then take the sample during the second phase, you get a more appropriate response in the schedule. If we don't use a root zone sensor and still want to get a good idea of what's going in the block substrates then this is the way. If you have access to root sensors, monitoring 24/7, then this is the way to collect data professionally.
So just a recap, in the first phase of the day we are building up water moisture in the substrate. The second phase they're pushing out and maintaining what should be the substrate and then phase three were pushing the crop vegetative or generative type responses overnight.
A lot of these responses also come with climate, so if you're looking at feeding responses and basing everything on nutrients keep in mind your 24-hour responses are based on different inputs from the climate as well and 24-hour averages can be much lower than what you expect. Let's say you like the room at 80° F in a vegetative state and if you drop down to 70° F degrees, you're going to get a generative response from the crop.
During the veg phase, the temperature between night and day are very close together promoting a vegetative response in the crop. In flowering stages, plants experience 12 hours of light and 12 dark where temperatures decrease 10° F or more. That temperature change is going to elicit a generative response in the crop. You can be in a veg room implementing generative steering protocols and conversely can be in the flower stages using vegetative steering protocols.
If you look at your crop thinking "this is looking really leafy", then you need to look at light, irrigation and climate because something is wrong. If you're in the flowering stage, you don't have to be always pushing generative plant responses. Keep in mind not to get stuck in any one mode while crop steering.
Steering with irrigation requires a long-term perspective, and it's important to balance your approach throughout the day. The Three Phase system focuses on maintaining the right moisture content and nutritive qualities in the substrate while triggering the desired plant response.
In conclusion, changing the EC in the substrate or the dripper can drive a generative or vegetative response. Steering involves a balancing act, taking into account various triggers throughout the day and considering changing climate conditions. Don't solely rely on nutrient inputs.
Thank you to the Grodan team for hosting this enlightening slides on the basics of crop steering protocols for achieving vegetative and generative plant responses in both veg and flower stages.