What is Cal Mag Deficiency and what is the solution to this problem?
First things first, Cal is short for Calcium and considered a secondary plant nutrient. Although it is considered a secondary nutrient, in Cannabis it is used almost as much as the macronutrients. Mag is short for Magnesium and also considered a secondary plant nutrient. It is not used in such large quantities as Calcium (roughly 5/1), but absolutely essential for the production of chlorophyll as it is the central molecule used in the formation process.
Cal Mag Deficiency is kind of a misnomer. Calcium deficiency is definitely a thing, Magnesium deficiency is definitely a thing, and both things can be going on at the same time, but in an indoor situation it is very unlikely. First, let's talk about each deficiency independently, Cal and Mag being deficient together, and then really expound on another potential problem related to Calcium, Magnesium, and Potassium and their relationship in your root zone.
Calcium deficiency is actually somewhat uncommon indoors, but not uncommon in field planted outdoor crops. Frequently, plants can process more calcium than is available. Deficiency signs may be difficult to detect. They start with weak stems, very dark green foliage, and exceptionally slow growth. Young leaves are affected, and they show signs first. Severe calcium deficiency causes new, growing shoots to develop yellowish to purple hues and to disfigure before shriveling up and dying, bud development is inhibited, the plants are stunted, and harvest is diminished. Growing tips could show signs of calcium deficiency if the humidity is maxed out. At 100%, the stomata close, which stops the transpiration to protect the plant. The calcium that is transported by transpiration becomes immobile.
Magnesium deficiency is possible indoors. The lower leaves, and later the middle leaves, develop yellow patches between dark, green veins. Rusty-brown spots appear on the leaf margins, tips, and between the veins, as the deficiency progresses. The brownish leaf tips usually curl upward before dying. The entire plant could discolor in a few weeks, and if severe, turn a yellow-whitish tinge before browning and dying. A minor deficiency will cause little or no problem with growth. However, minor deficiencies escalate and cause a diminished harvest as flowering progresses. Most often, magnesium is in the soil but is unavailable to the plant because the root environment is too wet and cold or acidic and cold. Magnesium is also bound in the soil if there is an excess of potassium, ammonia (nitrogen), and calcium (carbonate). Small, undeveloped root systems are also unable to take in enough magnesium to supply heavy demand. A high EC slows the water evaporation and will also diminish magnesium availability.
In this paragraph, and the proceeding one, it would be appropriate to discuss how to solve a Calcium deficiency or magnesium deficiency. Offering those solutions without a proper diagnosis in most cases is going to be useless. Before adding one or both of these nutrients which could definitely make the problem worse you really need to figure out what the problem is. We are available for a one on one plant problem diagnosis session, or can give you a no frills, inexpensive, easily repeatable recipe for growing amazing, heavy yielding flowers every time. Our Cannabis Plant Problem Diagnosis book can be found here (coming soon) if you're looking to figure it out on your own.
Before you jump to any diagnostic conclusions, let's discuss antagonism. A nutrient antagonism is when an excessive concentration of one nutrient inhibits the uptake of another. Since K, Ca and Mg have similar properties, and are taken up in a similar fashion, too much of one nutrient can inhibit the uptake of another nutrient. For example, if the concentration of Ca gets too high, it can impede the uptake of Mg. Or if the K concentration gets too high, Ca uptake can be inhibited. Antagonism-induced nutrient deficiencies can cause a variety of crop disorders, ultimately reducing productivity (yield) and quality of your medicine. To keep K, Ca and Mg in balance, the water, media, fertilizer and pH adjusters used to make up and maintain nutrient solutions should all be evaluated. By starting out with the right proportions of K:Ca:Mg, and maintaining them throughout production, antagonisms and the deficiencies they induce can be avoided.
The most proactive approach to managing nutrient antagonisms after mixing fertilizers is to perform regular nutrient solution analyses. Check the quality of water used to make up the nutrient solution. Specifically, look at the alkalinity and hardness. If water alkalinity is high, there will be hardness. It is common for highly alkaline water to come from limestone (calcium carbonate) aquifers. Hardness is a measurement of the combined Ca and Mg of water and is expressed as equivalents of calcium carbonate. The Ca and Mg in water resulting from hardness will be available for uptake by plants, so it needs to be considered when formulating nutrient solutions together.
The next thing to consider is fertilizers. Specifically, how much K, Ca and Mg will be added to the water from fertilizers? This starts with fertilizer types. If a single bottle fertilizer is used, the proportion of nutrients to one another is fixed. If a two or three bottle fertilizer is used, there is some opportunity to adjust the concentrations of Ca and K with the calcium nitrate and the second bottle with other macro- and micronutrients, respectively. Fertilizers mixed from individual salts are the most flexible, as there is no fixed proportion of nutrients with one another and all nutrients can be adjusted to hit target ratios.
Finally, look at how pH is adjusted. If acid is most frequently used to decrease pH, no K, Ca or Mg is being added to systems as sulfuric or phosphoric acids are most commonly used and contribute sulfur (S) or phosphorous (P) to nutrient solutions. Alternatively, if an alkali or base is added to increase pH, K concentrations may climb with their addition. Potassium carbonate or potassium bicarbonate are commonly used to increase pH, and K increases with their use.
The most proactive approach to managing nutrient antagonisms after mixing fertilizers is to perform regular nutrient solution analyses. When nutrient solution samples are submitted to a commercial laboratory for nutrient analyses, the concentration of each essential element in the nutrient solution is measured and adjustments in nutrient management can be made based on plant uptake and residual nutrient concentrations.
The relationship between K, Ca and Mg is a unique one due to their interactions with one another. These nutrients are not only essential for plant growth, but their deficiencies can cause specific problems in Cannabis production. Avoiding antagonism-induced deficiencies is important for maintaining productivity and quality.
Growing does not need to be difficult and complex! We are available for a one on one plant problem diagnosis session, or can give you a no frills, inexpensive, easily repeatable recipe for growing amazing, heavy yielding flowers every time. Our Cannabis Plant Problem Diagnosis book can be found here (coming soon) if you're looking to figure it out on your own.
Check out this great video from an old friend and colleague on Magnesium Deficiency.
As well as this one regarding Calcium deficiency.
Copyright © 2022 Cal Mag Deficiency Diagnosis and Solutions - All Rights Reserved.