Fixing your ph in the grow
Considering pH In Your Grow
Maybe you’ve never heard of pH before, and that’s okay.
I aim to give you a quick (but quality) overview of pH and how to optimize your plant’s health by adjusting your water or nutrient solution’s PH. For the growers who’ve been at it, this will be a bit of a refresher for you.
pH, or potential hydrogen, is one of the most critical aspects of irrigation.
Whether you are a beginner or have been growing for a long time, without a proper understanding of how it affects nutrient uptake, gardeners will spend a lot of unnecessary time wondering why their plants don’t look happy.
pH or potential hydrogen is the negative log of the concentration of positively charged ions in a solution. In simple terms, pH is a way to measure how acidic or how basic your solution is and allows you to get a general idea for the way the plant is taking up certain ions.
Here is a breakdown of the pH scale:
0-6: Acidic
7: Neutral
8-14: Alkaline (Basic)
The pH scale is logarithmic, meaning each whole number change on the scale represents a tenfold change in acidity or alkalinity.
For example, a nutrient solution with a pH of 5 is ten times more acidic than a pH of 6.
My BlueLab pH pen. Keep reading for more info on this!
Your PH is the problem. here’s how to fix it.
Your pH might be off, and you don’t even know it.
pH problems can pop up sneakily in the root zone or the feed without proper monitoring. For example, a hard dryback can send your EC through the roof, causing the pH to vary from your desired setpoint.
Though the perfect pH needed will vary from media to media and variety to variety, there are general ranges to work within to get started.
In order to optimize your irrigation process, you should have an in-depth understanding of feed pH, growing media pH, and runoff pH.
Feed pH
Each growing medium has a different ideal pH range.
Soil growers generally want to keep a higher pH than an inert, hydroponic growing media.
If you are growing in soil, a pH of 6.0 - 6.4 is ideal, but hydroponic growing media should be fed a lower pH solution between 5.6 - 6.0. Peat moss can handle feed pH values as high as 6.1.
Keeping feed pH consistent is essential for uniform nutrient delivery.
As mentioned above, different cannabis varieties will have different ideal feed pHs to satisfy certain nutrients they need more or less.
It’s ideal to pair cannabis varieties with similar preferences to each other to optimize their performance under said conditions. For example, if you notice that two varieties work better when fed a 5.9 pH as opposed to a 5.6, it’s ideal to pair those two for production.
Those using synthetic nutrients will have more control over modulating this variable than those using organic inputs.
MEDIA PH
Just as your feed pH should remain consistent, your media pH should also. This can become a challenge as your plants grow.
Your plants will demand a higher nutrient concentration within the growing media and without proper management of your irrigation events and drybacks, you can run into pH fluctuations and plant health will suffer.
The positive ion concentration increases in the media as the plants consume negatively charged ions. This increase in positive ions caused the pH to go down in the media over time.
The higher the nutrient concentration in the growing media relative to each variety’s desired media EC, the higher the pH can rise. The less nutrition the media inherently has or holds on to, the lower the pH needs to be to optimize nutrient uptake.
In either case, it’s not the end of the world. Those growing in hydroponic media will have the ability to flush and recharge or pH balance the media consistently. You can do this with a full-strength, 75% strength, or 50% strength nutrient solution applied for 7-10 seconds into the growing media.
Never go below 50% of your typical feed concentration as you can cause osmotic shock to your plants and damage the plant tissue at the cellular level. Regardless of strength, each solution should be pH-balanced for your media of choice.
During this time, you should see runoff leaving the bottom of the growing media itself, signaling that you are adequately flushing the substrate with the new solution.
Flushing in a soil-based media is technically possible but not as efficient as flushing within hydroponic growing media.
Soil growers will primarily rely on nurturing the microbial life in the root zone to balance the pH by communicating with the root system.
You can also actively monitor your root zone pH in soil and soilless systems with the technology offered by Growlink and Aroya. These companies offer sensor technology to monitor and log various metrics in the root zone.
Flower shot from a commercial run of mine.
Runoff pH
To complete your visibility over pH during the process of irrigation, it’s also important to look at your runoff or leachate pH values. You won’t be steering your entire crop off of runoff pH data alone, but recording runoff pH completes the puzzle with an additional data point that lets growers know how their plants are uptaking the nutrients in the media. When growers consider this data point in tandem with feed pH and media pH, an educated decision can be made about how to alter the fertigation solution or schedule for better nutrient uptake. If your runoff pH is lower than your inflow or feed solution, it could mean a few things:
A. Your plants could be happy with the feed concentration, but have an imbalance of negative and positively charged ions due to consuming negatively charged ions like sulfates and phosphates. With a higher concentration of positively charged ions, the pH of the solution decreases.
B. You are feeding too high of a feed concentration to your plants, leading to nutrient lockout and pH drop.
C. A hard dryback can lead to a decrease in pH due to the accumulation of acidic ions in the solution.
A higher runoff pH than your feed solution suggests that your plants aren’t taking up certain nutrients efficiently potentially due to high feed concentrations. You’ll notice your plants struggle to uptake negatively charged ions like phosphate and iron.
It’s also crucial to take your runoff samples simultaneously concerning your irrigation. Meaning, take your samples at the same time each day. Otherwise, you will likely skew the data due to evaporation, rising EC and ionic concentration.
pH Pens/Probes
To get a pH reading, you’ll need a pH probe. I use a BlueLab pH Pen, which gives me an accurate pH and temperature reading of whatever solution I measure.
From the BlueLab website, it will cost just over $100. You can find cheaper pricing on Amazon, but remember that some models could be used.
To maintain these BlueLab pens over time, you’ll also need to purchase a bottle of storage solution, 4.0 pH calibration solution, and 7.0 pH calibration solution.
The storage solution offered by BlueLab is made of calcium chloride and helps preserve the probe itself.
These solutions are used to calibrate pH meters and monitors. Each solution calibrates the pH meter at 4.0 and 7.0 respectively.
Calibrating with both solutions is a common two-point calibration method used to cover a broad pH range.
If your budget doesn’t permit the immediate purchase of BlueLab’s products, other budget-friendly options available on various websites like Amazon for a fraction of the cost.