Secondary Common Plant Deficiencies

Recognizing Calcium and Magnesium Deficiencies

What’s up everyone, Dr. NPK here. Today’s post is about diagnosing some common secondary plant deficiencies and some potential remedies for them. I guess it’s finally time to devote a blog post to my “doctor” status, right? But for real…not a medical doctor so don’t listen to me in that realm, only chemistry! Over the next few months, I’ll detail certain elements and how to fix their respective deficiencies

A Word of Caution

The jackpot for scientists is a well-designed experiment. Scientists are always trying to setup a system that tests one variable. In science, it is important to note that you can’t make a conclusion (or diagnose a culprit) unless you are rigorously testing for one variable only! I cannot stress this enough. For example, let’s say your plants are not doing well. To help fix the problem, you change when you feed your plants as well as the quantity of fertilizer. The plants start to look better; you blame the amount of nutrients you were using. HOWEVER, because you changed two variables (time of feed + amount), you cannot make a definitive conclusion! I see these issues all the time with growers.

To be clear, I don’t say this to scare you; I just want to make sure you understand that sometimes identifying the culprit is harder than you think, and that it is important to have an open mind that there may be multiple issues (or variables).

Let’s Get to It….

Ever wonder why most calmag supplements contain both calcium and magnesium? Most formulators put these two vital nutrients together because it can be very difficult to diagnose one deficiency over the other. Also, calcium ions (Ca²⁺) and magnesium ions (Mg²⁺) typically behave the same way in your water solution; if you are getting nutrient lockout of one (e.g., calcium sulfate or calcium phosphate formation, the white salt at the bottom of your res), you are likely getting nutrient lockout of the other (magnesium sulfate is an exception, but magnesium phosphate is insoluble). Elite CalMag is our solution to blanketing any issues you may have with a lack of secondary nutrients. When I think of secondary nutrients, I think of chlorophyll, which is green. If I am deficient in these nutrients, my chlorophyll will be low, and I would expect lack of green color.

Calcium

Of the secondary nutrient deficiencies, calcium deficiencies tend to be more concerning, because calcium is also used in the growth of the plant’s cell wall. Things to look out for:

Yellowing at the top of the plant (calcium cannot migrate through the plant like other elements)
Weak stems (poor cell wall = poor growth)
Slow growth (and you’re sure your main macronutrients are correct)

If you are sure you are supplementing with the correct amount of calcium (remember, if you use RO, use Elite CalMag), a common issue I see with growers is their root zone pH is off. Calcium uptake in cannabis plants is pH-dependent! You should target 5.2-6.1 pH range to ensure proper calcium uptake. An easy way to tell if your plant is uptaking calcium is to use one of your calcium supplements, and measure your EC before the roots (but after the sump) and then after the root zone. If your EC doesn’t go down, it means your plant hasn’t taken in any of the nutrients (likely the calcium). Lastly, check your reservoir for calcium lockout (white solids in your reservoir). Usually these useless inorganic salts are formed when you mix the concentrates too quickly. Add each fertilizer product to your water res more slowly with good mixing so it has time to fully dissolve before adding the next fertilizer concentrate.

Signs of calcium deficiency. Spotty brown/yellow marks that usually affect the top of the plant.

Calcium Mobility

Calcium deficiencies will typically appear in newer leaves. This is because calcium stored in older leaves cannot be transferred to new growth as calcium is an immobile ion in the plant.

Magnesium

As I had mentioned before, magnesium deficiencies follow similar appearances to calcium deficiencies (chlorophyll, the whole brown/yellowing deal). There’s one key difference between them: calcium-caused browning affects growth from the beginning (and affects plants towards the top of the plant), magnesium-caused browning affects already-established leaves (e.g., they don’t “grow in yellow,”). Signs to look out for to start thinking it’s a magnesium problem:

curling down of leaves
yellow/browning outside of the veins
general plant droopiness (less telling, could be a variety of things)
above issues affect lower parts of the plant (unlike calcium, magnesium is a mobile ion in the plant).

Troubleshooting is similar to calcium deficiencies: check EC before and after root zone, look for nutrient lockout, confirm you’re in the right root zone pH (similar to calcium’s pH range) and make sure to supplement your RO water with Elite CalMag. Remember: magnesium deficiencies can be disguised as calcium deficiencies, so make sure to keep an open mind when troubleshooting!

Magnesium deficiency in cannabis. Note the yellowing is outside the plant veins.

Magnesium Mobility

Magnesium deficiencies will typically appear in older leaves. This is because magnesium is allocated to new growth as it is a mobile ion in the plant.

Closing Thoughts

Calcium and magnesium are two vital elements to grow good bud. Yellowing is often a sign of an impact on chloroplasts/chlorophyll, and it’s a good chance it’s related to the secondary nutrients (including iron, which we will discuss in a later post). Using Elite CalMag could solve all your problems with a single supplement!