The First in a Series on Clean Hydroponic Techniques, for the Cultivation of Cannabis (Part One)
Hydroponic Cannabis Principles
With most plants, this difference is not a big deal. As you'll begin to learn from my posts, cannabis is definitely not like most plants. One of the main differences being how the pH swing is handled in the reservoir.
Roots-In Hydroponic Systems
Simply enough, Roots-In Hydroponic systems are systems with roots constantly exposed to nutrient solution. Among other differences, there are strict temperature requirements, for success with roots-in hydro systems.
These systems include and are not limited to:
- NFT Nutrient Film Technique, roots are constantly exposed to a flow or nutrient solution.
- DWC Deep Water Culture, roots are constantly suspended in the nutrient solution.
- RDWC/URDWC Recirculating and Undercurrent-Recirculating Deep Water Culture
Cannabis roots are rather picky and have a narrow range where they're comfortable. They have problems with nutrient uptake at temperatures below 65F(18.3C), and begin to rot at temperatures above 69F(20.5C). Root Rot is not pretty.
Nutrient Solution Aeration
Cannabis requires a certain amount of oxygen in the nutrient solution. Not enough oxygen and the roots rot, causing plants to look as if they need water. Excessive amounts of room air, pumped through the solution, causes a temporary rise in pH. This rise in pH dissipates quickly when air levels are reduced, it does have an effect on nutrient absorption.
Pump air through a proper temperature reservoir without nutrients first. Check pH as you increase the amount of air being pumped through the reservoir. When you reach a point where the pH begins to rise, reduce the amount of air. Recheck pH at intervals while lowering air levels until the pH returns to 7.
Reservoir Management of pH Swing
Cannabis evolved with a constantly changing pH. Like most plants, the cannabis plant has the ability to store nutrient elements for a short time. As pH levels change, the ability to absorb certain elements changes as well. When a specific elment is being easily absorbed, the plant will fill up the storage for that element.
With roots constantly exposed to nutrient solution, the pH swing must happen in the nutrient solution itself. This is accomplished through some rather simple reservoir management techniques. The end result is a regular and cyclic pH swing.
Roots-In hydroponic cannabis has a comfortable/healthy/vigorous pH range of 5.4 to 5.8, in the root zone. When the full pH swing is accomplished, cannabis has full access to the entire range of elements needed for growth. A full pH swing has always produced, for me, the highest yeilds, potency and terpene/oil production.
Cannabis evolved with a pH swing, including the ability to fill and empty a certain reserve capacity for each element. When these reserves are nearly filled and emptied regularly, the cleanest cannabis is produced.
Nutrients are pH Down
When you add nutrients to your reservoir of water, the pH goes down. As the plants absorb those nutrients, the pH rises. This is a fundamental key to a natural pH swing in the reservoir. This can only be accomplished through proper setup and maintenence of the reservoir.
I have personally used the following methods to manage the same nutrient solution for over 4 months. At harvest time the solution was still clean and clear with healthy plant growth.
Roots-In Reservoir Setup
- Use clean water, 15ppm or less, to maximize these methods and the cleanliness of the end cannabis flowers. Any levels of contaminants above 15pp begin to affect pH, water filtered using reverse osmosis has a pH of nearly 7.
- Control Reservoir Temperatures as previously stated, nutrient solution temperatures above or below the comfort range will cause problems.
- Pharmaceutical Grade Nutrients because cannabis paints any contaminants and un-needed elements into new growth. Clean hydro is about growing plants without contaminants and pharmaceutical grade is 99.9% free of them.
- Nutrient Profile for Cannabis AND a Full pH Swing When cannabis is given a full pH swing, the cleanest cannabis comes from a carefully balanced mix of elements. An element available in excess, yet not easily absorbed, can become a contaminant, as soon as the pH swing raises the absorption rate.
- Provide Sufficient Aeration cannabis grows best when areation levels are at maximum. The maximum is just below the rate where pH begins to be affected.
Once you've filled the reservoir with water, nutrients are added to the strength necessary for the environment. This will significantly drop the pH below 4.
Add pH Up
I use a pharmaceutical grade pH up to bring the pH to 5.4. Unless you manage the reservoir for more than 3 months, additional pH up is generally unnecessary.
Add Clean Water and Check pH Daily
I add only reverse osmosis filtered water to my reservoirs. Each day I add water to re-fill what the plants have used. Each day I check the pH after adding the water.
As the days progress (like the chart above), the pH will go up. Again, this is the natural progress of plants absorbing nutrients from the water. When the pH reaches 5.8, we drop it back down.
Dropping the pH
Simply add enough nutrients to reach the starting strength when you first mixed the reservoir. You'll find that the pH has dropped back down to 5.4. Wasn't that easy?
Lather, Rinse, Repeat
This cycle continues until for several months with vegetative reservoirs, before needing to be dumped. Flowering reservoirs can be run, without dumping, for most strains under 4 months. This saves a significant amount of nutrients ($$) and water.
Roots-Out Hydroponic Systems
Look for a link in the comments below, I'll be posting it up as soon as it's finished. In it I'll describe Roots-Out Systems and how reservoir management is different from Roots-In Systems.
Be sure to read the preview to my book, hit the link to my neatly categorized blog posts below. ;) Feel free to ask your questions on Roots-In systems below. General cannabis questions will be answered in my Ask TheCleanGame thread. Thank you for expanding your awareness of cannabis...