The Importance of using CalMag in Coco

Calcium (Ca) and magnesium (Mg) deficiencies are common issues in coco coir cultivation. Understanding the relationship between coco coir and these essential nutrients is crucial for effective fertigation management. In this article, I will explain the fundamentals of cation exchange in coco coir. Why Calcium (Ca) and magnesium (Mg) supplementation is necessary when growing in coco. Additionally, I will provide guidelines on when and how much CalMag to use in the different stages of plant growth.

While cannabis fertilizers contain Ca and Mg, it’s important to note that coco coir itself requires a certain amount of these nutrients. The cation exchange sites in coco coir can bind with Ca and Mg, rendering them unavailable to the plant. Therefore, larger doses of Ca and Mg need to be provided to ensure a sufficient supply for the plants.

Buffering the cation exchange sites in coco coir prior to use is critical. You can refer to our tutorial, “Preparing and Buffering Coco Coir” for detailed instructions on this process. Even with thorough buffering or the use of pre-buffered coco products like Roots Organics, it’s still necessary to add additional Cal Mag supplement to all irrigation water during the grow.

Understanding Cation Exchange in Coco Coir

Coco substrate has a fairly high ability to hold onto nutrients. This is due to it having plenty of cation exchange sites. These are docking stations for cations, or positively charged ions, like calcium (Ca⁺²), magnesium (Mg⁺²), and potassium (K⁺). In addition, coco naturally comes with a high concentration of potassium, since it is part of the material itself. The plant utilizes these nutrients when needed after they rest in these exchange sites. It’s important to balance out the ratio of calcium, magnesium, and potassium found on the coco. This is so that the plant receives the correct balance for successful growth and to prevent deficiencies.

A good coco substrate arrives pre-buffered with a nutrient solution or includes instructions for self-buffering. To maintain the nutrient buffer, apply a specially designed solution to balance the calcium and magnesium needs. It is also important to water with sufficient drainage, every time you apply the nutrient solution. And, lastly but importantly, avoid applying plain water or a poor nutrient solution.

Damaging the Buffer

Pouring plain water over the coco damages the coco nutrient buffer. This displaces some calcium and magnesium from the substrate and replacing it with potassium within the coco medium. This movement happens due to the nutrient elements on the coco substrate striving for a concentration balance with the nutrient elements in the water. Consequently, the plant does not receive the correct balance of nutrients it requires, leaving the substrate imbalanced as well. During subsequent feedings with a proper nutrient solution, the coco substrate will attract some of the nutrients in order to restore its nutrient balance. As a result, continue to leave a nutrient shortage for the plant.
To resolve the issue, thoroughly flushing the coco with a balanced, complete nutrient solution is necessary, allowing some time for the coco buffer to repair itself.

Why Do You Need Cal Mag Supplement If the Coco Coir Is Buffered?

The reason is that coco coir is constantly breaking down. As larger coco coir fibers break apart, new surface areas and cation exchange sites are exposed, resulting in the coco coir extracting Ca and Mg from the nutrient solution. This reduces the availability of these nutrients for the plant.

When to Use Cal Mag in Coco

Cal Mag supplement should be added to all irrigation water provided to the plant throughout the grow. However, it’s important to note that when adding Cal Mag, you are not doing it for the plants themselves but rather to satisfy the coco coir’s needs. The amount of Cal Mag you need to add reflects the requirements of the coco coir, not the plant.

During the early stages of growth, fresh coco coir has the highest potential for breaking down, accelerated by the roots of growing plants. Young plants expend a lot of energy pushing their roots through the coco coir, contributing to its breakdown and creating an ongoing need for additional Ca and Mg. As plants enter the flowering stage, the coco coir becomes more stable, requiring less Cal Mag supplementation. This is advantageous, as bloom boosters can supplement the EC quota that Cal Mag supplements relinquish.

Choosing a Cal Mag Supplement

I personally use and recommend

I use and recommend General Hydroponics CaliMagic. It is formulated to deliver a high dose of Ca and Mg without significantly contributing to the amount of nitrogen, phosphorous or potassium. When selecting a Cal Mag product, be aware of the quantity of nitrogen (N) in particular. N is the first number in the three number set listed on all fertilizers, for Calimagic it is 1-0-0. Many Cal Mag products also deliver high doses of N, which can create problems with your nutrient element ratio.

, which provides a high dose of Ca and Mg without significantly impacting nitrogen (N), phosphorus (P), or potassium (K) levels. When selecting a Cal Mag product, pay attention to the nitrogen content, as it’s the first number listed in the fertilizer’s three-number set. Cal Mag products with high nitrogen levels can disrupt the nutrient element ratio.

How Much Cal Mag to Use

The specific dosage will depend on the Cal Mag product you are using. Cal Mag supplements have a significant impact on electrical conductivity (EC), requiring careful dosing. The amount of Cal Mag used will affect the doses of other nutrients added. To gain a deeper understanding of nutrient dosing and the importance of EC, I recommend reading our articles “Understanding Electrical Conductivity (EC) and Osmosis” and “Setting EC Targets”.

Due to its strong impact on EC, Cal Mag takes up a substantial portion of the “EC budget.” For instance, during vegetative growth, I recommend a nutrient solution with an EC of 1100-1200. However, a full-strength dose (5ml/gal) of Calimagic contributes an EC of about 800. This leaves only 300 EC for other nutrients in the budget. If you are confident in the buffering process, you may reduce the dose to accommodate other nutrients, particularly in late flowering. Nevertheless, some Cal Mag supplement should be added to every nutrient solution.

Cal Mag Doses During Vegetative Growth

It’s advisable to start with a full or nearly full dose, such as 5ml/gal for CaliMagic, accounting for approximately 800 EC. However, during the seedling stage, when plants require a very low inflow EC, dosing Cal Mag can be more challenging. Refer to our article “A Step-by-Step Guide to Growing Cannabis From Seed” for specific guidance on Cal Mag dosing for seedlings. If you start with the full dose and the plants do not exhibit Cal Mag issues, you can reduce the dose as you enter late vegetative growth.

For pre-buffered products like Roots Organics, a half dose may be sufficient initially. However, even with pre-buffered coco coir, inadequate Cal Mag supplementation can lead to Ca deficiency.

To ensure proper nutrient mixing, refer to our article “How to Mix Nutrients for Cannabis” which provides a comprehensive nutrient recipe schedule including the appropriate dose of Cal Mag and other essential components.

Cal Mag Doses During Flowering

If the plants are not experiencing Ca or Mg deficiencies, the Cal Mag dose can be halved during flowering. This adjustment is particularly important during mid to late bloom to allow for higher doses of phosphorus and potassium for optimal flowering.

By mid-bloom, plants should thrive with half the dose of Cal Mag used during vegetative growth. However, closely monitor your plants and be prepared to increase the dose if deficiency symptoms, such as brown spots on lower leaves, appear.

Calcium (Ca) and Magnesium (Mg) Deficiencies

Remember, using CalMag supplementation is crucial for maintaining the health and nutrient balance of your cannabis plants when growing in coco coir.

Calcium Deficiency

Magnesium Deficiency

By utilizing buffered coco and adhering to the guidelines provided, you should be able to prevent or effectively handle any calcium (Ca) and magnesium (Mg) deficiencies that may arise during your grow. However, in the event that you encounter any issues, feel free to visit our Grower’s Forum where our team will gladly assist you by answering any questions you may have.

Product & Equipment Guide

Set-up Your Grow

Growing Cannabis

About Our Product Recommendations

Here at 420 Grow Help, our primary goal is to assist growers in achieving the utmost success with their cannabis crops by providing accurate scientific information and sharing proven cultivation techniques. The products we recommend are the very ones we have personally chosen to purchase and use ourselves. We maintain a strict policy of not accepting sponsorships or advertising, and we only endorse products that meet our own high standards. For detailed product recommendations, please refer to our Product and Equipment Guide.

Please note that when you make a purchase through the links we provide, we may receive a referral fee. This is the primary source of revenue that supports and sustains 420 Grow Help. By clicking through our links and making purchases, you are directly contributing to our ongoing work. As an Amazon Associate, we earn from qualifying purchases.

Disclaimer:

The information presented on 420GrowHelp.com should not be regarded as financial, legal, or medical advice. It is your responsibility to familiarize yourself with and abide by the local laws and regulations pertaining to the cultivation, possession, and use of cannabis. Decisions regarding cannabis cultivation should be made in consultation with a lawyer or qualified legal advisor, while decisions regarding cannabis use should be made in consultation with a doctor or medical professional.

The Importance of using CalMag in Coco