If you are growing in bigger containers or pots – 2 gallons or more – chances are you’re watering much less often than a grower in a small pot or block. Because of this, monitoring runoff and making adjustments to the next feeding is critical to a healthy garden.
In this section we will discuss the best watering techniques for larger containers. If you are growing in rockwool cubes or smaller pots – 1 gallon or less – please follow the watering strategies found here instead.
Every watering we do in a cube, pot or container should always be to runoff. Runoff is extremely valuable data and unless you’re watching it, issues can be just around the corner.
Runoff provides a better picture of what the roots are living in. Just because you feed a nutrient solution at let’s say 900 PPM (1.8 EC), doesn’t mean the roots are living in 900 PPM as well. It’s very possible nutrients are accumulating and the PPM/EC of the root zone is increasing.
The chart below is a great runoff guide when growing in large containers:
After you mix any recipe from our feeding charts, you will use a meter to test the overall EC / PPM of the mixture. Whatever the recipe measures out to is the “Full Strength Nutrient Target” found on the top of this chart. If you need help converting PPM into EC, please use the chart here.
The left hand side of this chart is your runoff measured in EC. If you need more information on collecting runoff properly, please click here. Next, match your runoff EC value with your nutrient solution EC and find where the two intersect in the chart.
If you fall into the green zone, everything is good. You don’t need to adjust anything and you can continue on with another full strength feeding.
If you fall into the yellow zone, things are just beginning to accumulate. If you do another full strength feed, there’s a good chance you’ll push the plants into the red zone. If you are in this yellow section, you want to dilute or reduce your next feeding to 1/3, 1/2 or 3/4 strength.
You can do this by adding fresh water to your full strength mix and lowering the overall PPM/EC. If you are mixing a fresh batch, reduce every product by the same amount – for example, reduce every product by 50% – and mix up a new reservoir. This reduced feed will dilute the root zone and get the plants back into the sweet spot.
The goal of this reduced feed is to dilute the root zone and get runoff back down very close to your original “Full strength nutrient feed” value. It’s important not to dilute it too much or you’ll risk the plants being under-fed and hungry. How much you dilute the next feed will take some getting used to but with a little time and practice, you’ll get the hang of it in no time. After you’ve done a diluted correction, you’ll want to switch back to a full strength feeding next watering. Rise, wash and repeat!
If your runoff is in the red zone that says “increase”, your nutrient strength is too light. In this case, increase the strength of your feed using the guidelines and recommendations found on our feeding charts.
If your runoff is in the red zone that says “water”, there’s a lot of accumulation and signs of “lockout” or EC / PPM stress will show soon. In a situation like this, don’t panic and flush everything back to zero. What you want to do is feed fresh pH’d water until the runoff is diluted back down to the same EC / PPM of your normal nutrient feed. Feeding too much water will dilute things too far and the plants will go from over-fed to hungry and under-fed.
After the root zone has been diluted and corrected, make sure the next feeding is back to full strength and continue to monitor and make adjustments as necessary.