The Easiest Way to Know You’re Not Over- or Under-Feeding Your Cannabis Plants

The two most common things that go wrong for cannabis cultivators are 1) over- or under-watering plants and 2) over- or under-feeding them. Fortunately, there are tools available to help you avoid watering and feeding problems. A tensiometer gives you all of the data you need to ensure you’re watering correctly, and a chlorophyll meter tells you when your cannabis plants truly need to be fed.

What is a Chlorophyll Meter?

A chlorophyll meter is an inexpensive tool used to measure how much chlorophyll is in a plant’s leaf. You can get a reliable chlorophyll meter for just $200-$300, and the cost savings on labor and fertilizer that you’ll see over time will add up quickly.

The amount of chlorophyll in your plant directly correlates to the amount of nitrogen in the plant, and nitrogen is what drives feeding decisions in the first half of a cannabis plant’s growth cycle. Therefore, a chlorophyll meter takes the guesswork out of feeding because you’ll know in real-time and with great accuracy if you’ve overfed or underfed your plants.

A low percentage of chlorophyll in your plant tells you that you’ve been underfeeding while a high percentage of chlorophyll tells you the plant has enough nitrogen and continuing to feed would be wasteful, possibly dangerous for your plant. The goal is to get to maintain a stable number so your plants have the right amount of nutrients to achieve optimal growth.

Why Use a Chlorophyll Meter vs. Measuring Runoff EC?

When you feed your cannabis plants only when they truly need nutrients, your plants will be healthier, you’ll save employees’ time, and you’ll save money on fertilizer costs. There are two ways to measure whether or not your plants need fertilizer: by measuring runoff EC or measuring chlorophyll with a chlorophyll meter.

Measuring Runoff EC

Measuring runoff EC (electrical conductivity) requires following a manual protocol to detect the amount of electrical currents in the runoff water from the substrate your cannabis plants are grown in. The EC is higher when more nutrients are in the growing media, so a low EC measurement is assumed to mean you need to add more fertilizer while a high EC is assumed to mean you need to cut back on feeding.

The problem with measuring runoff EC is that it’s a very unreliable method to determine whether your plants actually need more or less feeding. Runoff from plants is wildly inconsistent, and the EC measurement has a huge error rate. That’s because electrical conductivity picks up a lot of nutrients besides nitrogen, no two cultivators do it exactly the same way, and the process itself is prone to mistakes. It’s a broad measurement that gives you a ballpark reading, but there are a lot of reasons why it could be inaccurate as a way to determine if your plants actually need fertilizer.

Runoff EC does not correlate directly to nitrogen levels in your plants, which is the most important feeding guide during the first six weeks of a cannabis plant’s growth. For example, your plants’ leaves may be yellow, so your grower could think the plants aren’t getting enough water. An EC runoff measurement may be low as well. However, there are actually many reasons why a plants’ leaves could be yellow, such as pests and pathogens, not necessarily nitrogen deficiency, which is the nutrient that guides feeding.

Bottom-line, EC runoff may not give you the information you need to get the best outcomes and avoid creating more problems.

Chlorophyll Meter

Measuring the amount of chlorophyll in your plants is the most accurate way to manage feeding. Since you know how much nitrogen is in your plants based on the amount of chlorophyll (and chlorophyll and nitrogen correlate during the first six weeks of growth), you won’t have to guess about adding fertilizer. You also won’t have to rely on following the overly-generalized, and sometimes inaccurate, feeding chart from the fertilizer company whose goal is really just to sell you more fertilizer.

When you know exactly when your plants really need to be fed, you’ll save a significant amount of time and money on labor and fertilizer costs, and your plants will grow healthier. This is especially important in the early stages of growth when you need to get plants established and get the right root structure.

Chlorophyll meters are the best way to measure nitrogen levels in real-time, but they’re usefulness is limited to the critical first six weeks or so of the plant cycle. After the second or third week of the flowering stage, the process of plant growth is no longer driven by nitrogen. At this point, growth is driven by phosphorous and potassium.

Therefore, using a chlorophyll meter during the first six weeks or so of the plant cycle when growth is driven by nitrogen is critical to future-proof your cannabis plants. Chlorophyll meters are extremely accurate and can help you establish healthy plants in the early stages of growing, so things are less likely to go wrong in the later stages.

How to Use a Chlorophyll Meter in Your Cannabis Cultivation Facility

Chlorophyll meters are extremely easy to use. You just insert a leaf into the meter (or hold a light beam to the plant depending on the type of meter you use), and you’ll get instant data that tells you the real-time chlorophyll level in your plant.

At bio365, we’ve tested many chlorophyll meters and recommend the atLEAF chlorophyll meter. It’s inexpensive, and we’ve found it to be as accurate as really expensive chlorophyll meters. It’s the chlorophyll meter we use.

Key Takeaways about Using Chlorophyll Meters to Feed Cannabis Plants Correctly and Save Money

Chlorophyll meters are inexpensive and easy to use. Small growers and large growers can grow healthier plants and save money with this one important tool. If your facility uses a grow software, you can even log data from the chlorophyll meter into your software. It only takes about 10 minutes to learn how to use a chlorophyll meter, and even entry-level team members can use them. Bottom-line, you’ll get a high return for a low cost.

At bio365, we recommend using a chlorophyll meter during the first six weeks or so of the growth cycle to ensure you’re not over- or under-watering your plants during this critical time. If you’d like to learn more about chlorophyll meters, nutrients, feeding, and more, contact us and talk to a soil expert.