Garden spade lifted with soil, taking a deeper look at soil nutrients

A Deeper Look at Soil Nutrients

When growing cannabis, many people forget to pay close attention to the nutrients in their soil; however, this oversight can be detrimental to plant health. Understanding how different macro and micronutrients affect each stage of plant development is important to grow cannabis successfully.

Cannabis plant closeup to leaves, highlighting that Nutrients move within healthy soil, supporting plant growth
Nitrogen, phosphorus, and potassium are the three most common nutrients in growing cannabis; however, there are many other macro and micronutrients that are essential in plant growth.

Last time, in “Soil Nutrients for Cannabis: A Beginner’s Guide”, we learned about the basics of soil nutrition. We covered the “Big 3” macronutrients and saw how each plays a crucial role in optimal cannabis crop growth.

In this post, we will take a deeper look, beyond the typical nitrogen, phosphorus, and potassium requirements. We will talk about the important secondary macronutrients, as well as micronutrients, that cannabis plants need to grow. We will also discuss how nutrients move in the soil, from mobility to lockout. 

There’s a lot to know about the nutritional health of your soil, and BlueSky Organics can help. To start, let’s take a look at macro vs. micronutrients. 


Macro vs. Micronutrients

The main difference between macro and micronutrients, are simply the quantities needed by the plants for optimal growth. Secondary macronutrients are not needed by plants in quantities as large as the “Big 3” macronutrients, but are still just as important and are needed in sizable amounts

On the other hand, micronutrients are minerals found in trace amounts in the soil. Some of these micronutrients exist in quantities of less than 0.1% of the lithosphere. Though they are only present in very small amounts, they are just as important as macronutrients in creating the ideal conditions for your cannabis crop to thrive. 

Before we learn about the different key secondary macronutrients and micronutrients, let’s briefly define two important concepts: “Nutrient Lockout” and “Nutrient Mobility”.


Nutrient Lockout

Barren cropland soil highlighting nutrient lockout in growing cannabis
Nutrient lockout and nutrient mobility are two important concepts related to growing healthy cannabis plants; nutrients must be able to move from the soil into the plant, and also be present in amounts that aid plant growth.

In short, a nutrient lockout is when conditions in growing soil prevent your plant from accessing the macro and micronutrients needed for healthy plant growth. This can be either having the wrong pH, as covered in our “Understanding Soil pH” post, or by not having the correct nutrient balance.

When you have a nutrient imbalance, with too much or too little of a macro or micronutrient, you will run into problems such as nutrient lockout. This can prevent your plant from obtaining the nutrients it needs, and, in serious cases, even be toxic to your plants.


Nutrient Mobility in Plants

Nutrient mobility is how easily a nutrient can be transported from older leaves to areas of new growth. This mobility is important because as plants grow, they’ll be in constant demand for nutrients. These nutrients need to be delivered to areas of development, whether from existing reserves or directly from the soil. 

A helpful analogy is to think about building a house. If you can’t take your hammer and nails with you as you build the next room, and you need to leave and purchase more from the store each time you progress, it’s going to be really hard to get anything done. Plants must also be resourceful and efficient, storing nutrients and mobilizing them when needed.

hand lifting up soil from a pile, illustrating that the difference between mobile and immobile nutrients is important
Starting with a good quality soil is the first step in aiding nutrient mobility.

In plants, mobile nutrients are able to be stored and shifted to fresh new leaves when needed. Immobile nutrients, on the other hand, cannot be stored and are therefore in constant demand. This biological phenomenon can be helpful in figuring out which nutrients you might be missing in your soil

A good rule of thumb is comparing older and newer leaves. If the older leaves look sickly, your plant is most likely hungry for mobile nutrients. If the newer leaves are stunted, your plant is probably lacking an immobile nutrient.

Another thing to keep in mind is that there is a difference between how nutrients move through the soil, and how easily they are taken up by the plant. A nutrient might be mobile in soil, but immobile within your plant. Giving your plants the nutrients they need starts with good quality soil and soil amendments, so let’s dive into the different types of macro and micronutrients.  


Secondary Macronutrients

Calcium (Immobile)

Calcium plays an essential role in regulating plant growth, as well as a plant’s response to stress. Even though calcium levels may be high in the soil, your cannabis plant may not be able to use the calcium due to high levels of phosphorus or nitrogen present (this is an example of nutrient lockout).

The easiest way to spot calcium deficiency in your plants is if leaf growth is uneven, the leaves are curling in, and black spots are present, usually on the tips of the leaves. However, recognizing the problem at this stage can often be too late. It’s important to know the components of your soil before you start growing, to prevent nutrient deficiencies.


Magnesium (Somewhat Mobile)

Small plant growing in the soil with sunshine behind, highlighting micronutrients in the soil
Chlorophyll is a green pigment, which aids in the absorption of light. Without this molecule, plants cannot obtain the energy they need to grow and thrive.

Even small fluctuations in magnesium levels can have big effects on how plants grow. Magnesium is required in plant development, as it is the central atom of chlorophyll and is required to form the molecule. Chlorophyll is vital to the process of photosynthesis, which is how plants harness energy from light. Without it, your plants will not grow to meet their potential.


Sulphur (Immobile)

Sulphur, like magnesium and iron, is very important for photosynthesis. Sulphur is also a key ingredient for the amino acids, cysteine and methionine. These amino acids both play a role in plant growth and development

Sulphur deficiencies occur when there isn’t enough organic matter content in the soil. Sulphur deficiency is often misdiagnosed as nitrogen deficiency, which can make the sulphur deficiency even worse. To avoid this mistake, take into note that sulphur is not as mobile as nitrogen, so the symptom of leaves yellowing will show up in the younger, fresher leaves first.



Boron (Immobile)

Boron plays a variety of roles in plant development. It helps to maintain plant cell walls, which keeps your plant standing straight. It also ensures that the plant cells divide properly, resulting in efficient plant growth. Without boron, you’re likely going to have a low plant yield

Cannabis plant buds, for which the micronutrient Boron is essential
Boron is a micronutrient that is responsible for many growth processes, including the development of healthy cannabis buds.

Even if your plants survive, lack of boron in your soil leads to poor development of plant reproductive structures. This means plants with less growth and fewer flowers, and of course, less flowering buds. For most growers, abundant, high-quality buds are the end-goal; having the right amount of boron can help get you there.


Copper (Immobile)

Copper is a micronutrient that prevents plants from wilting and also improves their ability to take up nitrogen, one of the Big 3 macronutrients. 

Copper also regulates chlorophyll production. This means that deficiencies in copper can lead to leaves that are either yellow in colour (known as chlorosis) or a green that is too deep

Due to copper’s importance in various plant growth processes, plants lacking copper often fail to develop or are stunted in growth. In some cases, the plants may not even grow at all, and may not make it past a seedling state.


Iron (Immobile)

Plants growing outdoors in the sun, highlighting that iron is an essential micronutrient for plant growth
Iron is a micronutrient that aids in the production of chlorophyll, the green pigment involved in photosynthesis. Iron also aids in nitrogen uptake, a process that is essential for plant health.

In our “Microbial Products: Working for Your Soil” post, we talked about how tiny microbes in your soil can help your plant access the iron that it needs for healthy growth. Iron is required for the formation of chlorophyll and is also fundamental to the uptake of nitrogen, one of the Big 3 macronutrients.

A mild form of chlorosis, known as interveinal chlorosis, is a common symptom of iron deficiencies. Interveinal chlorosis results in the veins of the leaves remaining green, while the leaf tissue between them begins to pale. In this situation, the more yellow the leaf gets, the more serious the problem.


Manganese (Immobile)

Manganese plays three main roles in plant development: photosynthesis, nitrogen metabolism and disease resistance.

In photosynthesis, manganese assists iron in the formation of chlorophyll. Their close relationship is not always a good thing, as high levels of manganese can cause nutrient lockout of iron. For this reason, deficiencies in manganese can often be confused with deficiencies in iron.


Molybdenum (Immobile)

Cannabis plant growing under a purple UV light, highlighting that Zinc helps plants deal with light stress
Zinc is a micronutrient that helps plants deal with stressors, such as heat, light, and microbial contamination.

Similar to the role of iron, molybdenum aids in nitrogen processing. This introduces the issue of molybdenum deficiencies being masked, as the symptoms of stunted growth and yellow leaves are shared. Thankfully, molybdenum deficiencies are rare; however, it is still wise to keep this micronutrient in mind when identifying deficiencies.


Zinc (Immobile)

Zinc has many roles in cannabis plant growth. One of its main roles is helping plants fight against stressors, such as temperature fluctuations, light, and fungal infection. Zinc deficiencies can cause major headaches for growers, as plant resilience is important in both indoor and outdoor growing environments. Zinc is also crucial in flower development, so deficiencies can result in longer times for cannabis plants to mature.

Uptake of zinc by plants is inhibited by excess phosphorus, calcium, iron, and copper levels in the soil, while zinc works in tandem with nitrogen and potassium. Symptoms of zinc deficiency include stunted growth, small leaves, the aforementioned susceptibility to disease, and lower yields.

BlueSky Organics Vit-Alive micronutrient booster
Compost teas, such as BlueSky Organics Vit-Alive, are great sources of macro and micronutrients for optimal plant growth. They boost the beneficial microorganisms in the soil, maintaining a healthy plant-soil ecosystem.


What Blue Sky Organics Can Offer

Macronutrients and micronutrients are key ingredients in the recipe for cannabis growing success.

A quick way to ensure you have the perfect macro and micronutrient balance in your soil is to use Blue Sky’s Vit-Alive Dry Compost Tea and Organic Reactor topdress. The addition of important microbes, covered in our “Microbial Growers: Feeding Your Soil” article, also allows your plant to make the most of these nutrients. These microbes can be found in Blue Sky’s Super Soil, along with many other plant-loving soil amendments.

With a super-soil for nutrient mobility and the right combination of macro and micronutrients to prevent lockout, your plants will be fully nourished and ready for optimal growth. At BlueSky Organics, we’ve created award-winning formulations that have optimal nutrient combinations. We’ve also created an informative growing guide, to take you through each growing step until your potent cannabis flowers are ready for harvest.

We’re passionate about growing high-quality, organic cannabis; it’s not just what you grow, but what you grow it with.