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Cannabis is a versatile plant that can grow in a variety of conditions, but it does have specific nutrient requirements that vary depending on the strain and the stage of growth. Here, we’ll help you choose the right nutrient mix for your plants and experience level.
Nutrient Requirements for Cannabis
When it comes to growing cannabis in soil, it's important to understand the difference between macronutrients and micronutrients.
Cannabis requires both macronutrients (i.e. nitrogen, phosphorus, and potassium) and micronutrients (i.e., calcium, sulfur, magnesium, copper, iron, manganese, molybdenum, and zinc) for successful growth.
Macronutrients are responsible for important functions such as photosynthesis, energy storage and transfer, and the development of strong roots and healthy foliage. Micronutrients are responsible for functions such as enzyme production, chlorophyll formation, and overall plant metabolism.
Most commercially available soils have fertilizers and nutrients in them and will not usually require additional fertilizers and nutrients during the first month or two of growth. It is important for growers to use a balanced fertilizer that provides both macronutrients and micronutrients in the right ration for the plants to grow healthy.
Cannabis typically requires the use of more nitrogen (N) during the vegetative growing cycle. During the flowering cycle cannabis will generally require an increase in phosphorus (P).
Nitrogen is essential for the production of chlorophyll, which is vital for photosynthesis, and it helps to build strong stems and healthy foliage. Phosphorus is essential for the development of strong roots and healthy buds, and potassium helps to regulate water balance and improve overall plant health.
Nitrogen (N) requirements also vary with light intensity and temperature. During “Hot” conditions (more than 90 degrees Fahrenheit), the plants will require 10 to 20% less nitrogen.
During cool periods (less than 60 degrees Fahrenheit), the plant will require 10 to 20% more nitrogen. For intense light (greater than 80 watts per square foot), the plants will require more nitrogen (N) and for low light conditions (less than 25 watts per square foot), the plants will require less nitrogen (N).
Cannabis Nutrients Deficiencies
Watch the plants closely for any changes or signs of nutrient deficiencies and disorders. Nutrient deficiencies in cannabis plants can offer when the plant is not receiving the necessary nutrients to grow and thrive.
These deficiencies can manifest in various ways, including stunted growth, discoloration of leaves, and overall poor health. Some of the most common nutrient deficiencies in cannabis plants include the following:
- Nitrogen deficiency: Nitrogen is an essential macronutrient that is necessary for the production of chlorophyll and the growth of leaves and stems. A nitrogen deficiency can result in the yellowing of the lower leaves and slow growth.
- Phosphorus deficiency: Phosphorus is essential for developing strong roots and healthy buds. A deficiency can result in slow growth, purple or reddish discoloration of the leaves, and small, poorly developed buds.
- Potassium deficiency: Potassium is necessary for regulating water balance and overall plant health. A deficiency can cause yellowing around the leaf edges, wilting, and a lack of resistance to pests and diseases.
- Iron deficiency: Magnesium is necessary to produce chlorophyll and overall plant metabolism. A deficiency can cause yellowing of the leaves, curled leaves, and lead to stunted growth.
It's important to note that the symptoms of nutrient deficiencies can be similar to those caused by other issues, such as pests or diseases, so it's important to properly diagnose the problem before attempting to treat it. In addition, sometimes over-fertilization can lead to nutrient burn, which can cause similar symptoms as deficiency.
Soil-Based Products and Cannabis Nutrients
Cannabis compost tea is a liquid solution made by steeping aged compost in water. The process of making compost tea involves adding a source of bacteria and fungi, such as molasses or fish hydrolysate, to the compost. These microorganisms are then extracted into the water and can be used as a fertilizer for cannabis plants.
Compost tea is rich in beneficial microorganisms, including bacteria and fungi, that can help to improve soil health and increase the availability of essential nutrients to the cannabis plants. These microorganisms can help to break down organic matter, create a more porous soil structure, suppress the growth of harmful pathogens, and suppress pests.
Compost teas work best in soil-based systems because the solids and particles that make up the tea can cause problems with hydroponic equipment.
When the tea is applied to soil, the solids and particles are able to settle to the bottom of the container and can be removed easily, without clogging or blocking the equipment. The microorganisms and nutrients in the tea are then able to be absorbed by the roots of the plants and improve the health of the soil.
However, in hydroponic systems, where the plants are grown in nutrient-rich water rather than soil, the solids and particulates can clog pumps and other equipment, causing damage and reducing the efficiency of the system.
The microorganisms and nutrients in the tea can also be difficult to control in a hydroponic system, leading to imbalances in the nutrient solution and potentially harming the plants.
Organic fertilizers and additives that can be used in soil-based systems are:
Ammonia – (NH3) is a gas containing 82% nitrogen, often used as a foliar feed in its aqueous form. It is a highly concentrated form of nitrogen and can be used to quickly boost the soul's nitrogen level. Use it with caution, as over application can lead to nutrient burn.
Cottonseed Meal -A byproduct resulting from oil extraction from cottonseed with a nitrogen content of 67%. Generally, it is used as a partial, slow-release nitrogen source in mixed fertilizers. It is also a good source of other nutrients such as potassium and phosphorus.
Blood Meal – Blood meal is a byproduct of the meatpacking industry and has a nitrogen content of 12 to 14%. The nitrogen is available quickly, but it does little for the mechanical properties of the soil.
Urea – Urea is a white crystalline compound containing 46% readily available nitrogen. This affordable form of nitrogen fertilizer is usually made from anhydrous ammonia (NH3) and is easy to handle, store and transport.
Fish Emulsion – Fish emulsion is prepared from non-edible fish and waste from fisheries. It has about 8% nitrogen. It is rich in nitrogen, phosphorus, and potassium, and it is also a good source of micronutrients like zinc and iron.
Bone Meal – Two kinds: raw and steamed. Steamed bone meal has less nitrogen than raw, but more phosphoric acid. This material releases its nutrients slowly so it can be used without fear of injuring the crop.
Rock Phosphate – Mineral occurring in deposits throughout the world. Its effectiveness is dependant on its degree of fineness and the reaction of the soil. It's a slow-release fertilizer and it can take a long time to break down and become available to the plants.
Super Phosphate – A source of phosphoric acid in complete fertilizers and a direct treatment of soils deficient in phosphorous but well supplied with nitrogen and potassium. It's a fast-acting fertilizer and it's a good source of phosphorus, but it can cause an increase in soil pH.
Slag – Finely ground byproduct of steel manufacture. Its free lime content makes it of special value in the reclamation of acid soils. It's a slow-release fertilizer and it can help to improve soil structure.
Wood ashes – Rapidly absorbable form of potassium that will raise pH because it is alkaline. It's important to be aware that wood ashes also contain high levels of salts that can be harmful if not used in moderation.
Seaweed – Contains a host of macro- and micro-nutrients, helps in water retention and absorption, and aids in weed prevention.
Growth and Flowering Supplements and Additives
There are more cannabis growth supplements, bloom supplements and stimulants, root stimulators and additives available than can be easily described here.
All supplements and additives must be added with caution to prevent any nutrient disorders, over-fertilization or nutrient burns. We will provide an overview of what is commonly available.
Fulvic Acid – used as a growth stimulator. Full acid is a natural acidic organic polymer that is extracted from humus found in soil, sediment, or aquatic environments.
Humic Acid – a principal component of humid substances, which are the major organic constituents of soil, peat, coal, many upland streams, lakes and ocean water. It is produced by biodegradation of dead organic matter. It is not a single acid; rather, it is a complex mixture of many different acids.
Gibberellic Acid – a hormone found in and extracted from plants. It is a naturally occurring plant growth regulator, which may cause a variety of effects including increasing the number and size of buds and the stimulation of seed germination.
Amino Acid – the key elements are carbon, hydrogen, oxygen, and nitrogen. Amino acids are critical to life and have many functions in metabolism. One particularly important function is to serve as the building blocks of proteins.
Enzymes – proteins that increase or decrease the rates of chemical reactions. At this time there are limited products available that claim to promote the use of enzymes for improving and increasing the growth of medical cannabis.
Carbohydrates – plants require sugar and carbohydrates in order to have enough energy for intense flowering periods and rigorous growth. The logical solution would be to just add sugar to the nutrient solution right? Many have tried this and often molasses is used as a simple sugar additive. The problem with this is that the sugar is not as easily taken-in by plants in this form.
It is better to add a carbohydrate additive, which is designed to make these carbohydrate supplements easier for the plant to take in. By using these additives, a grower can expect the plants to have sweeter tasting fruits, increase their essential oils, and nourish the plants to prepare them for intense flowering periods. If possible look for a carbohydrate additive that is organic, and combines easily with the rest of the nutrients being used.
Silica based products – promote healthier and stronger plant growth. When the roots take up silica, it is deposited in the cell walls of the plant as a solid, rigid ‘quartz-like' matrix. This produces a ‘mechanically’ stronger plant, which enables superior leaf orientation and therefore greater rates of photosynthesis and growth.
It increases the weight and shelf life of fruit due to the physical accumulation of silica in plant cells. Silica increases a plant's tolerance to heat stress or “wilting”. It also increases resistance to fungal diseases, particularly mildews and botrytis. It resists fungal ingress by accumulating around the points of fungal attack.
Silica improves the healing rate and neatness of pruning wounds. This property is especially beneficial in commercial cropping of plants such as medical cannabis. Regular pruning of these species threatens the plant's survival due to the risk of disease penetration through the site of the pruning wound.
Finally, silica increases a plant’s tolerance to nuisance chemicals such as sodium and chloride.
Vitamin supplements – help a plant feel better when stressed and keep a plant healthy. Vitamins will help with resistance to fungal rots and insect attacks. While plants normally manufacture vitamins for themselves, if they have an external additional supply of them, they can then turn their energy to producing other elements they need, and thereby speed up growth.
Minerals – There are many minerals that are either required by the needs of the plant or are beneficial for improving the growth of the plant. Below are a few descriptions of minerals available for use.
Calcium-when added to the plants nutrient solution or to the soil it will improve the efficiency of nutrient uptake and encourage superior flowering.
Calcium – when added to the plant's nutrient solution or to the soil it will improve the efficiency of nutrient uptake and encourage superior flowering.
Citric acids – can be added as a chelator (binder) for improved availability and plant uptake of nutrients and fertilizers.
Sulfur based additives – will activate enzymes, process compost and manure fertilizers, liberate roots systems and help balance soil pH.
Mycorrhiza – this is the relationship between the plant roots and beneficial fungi. Mycorrhizal products increase plant growth, nutrient and water uptake and improve soil structure.
Manufacturing Compost Tea
Compost tea for cannabis can be easily made by soaking or steeping compost in water. The resulting compost tea is used for either a foliar application (sprayed on the leaves) or applied to the soil.
We all know that compost is a wonderful addition to soil and helps gardens grow better. The plants can benefit even more by using compost tea.
Using compost tea to replace chemical-based fertilizers, pesticides, and fungicides, makes the cannabis garden safer and is more protective of the environment. Compost tea:
- Increases plant growth
- Increases nutrient availability
- Improves soil structure
- Provides nutrients to plants and soil
- Provides beneficial organisms
- Helps to suppress diseases and pests
- Replaces toxic garden chemicals
- 2 five-gallon buckets
- 1 gallon mature compost
- 1 aquarium pump
- 1 gang valve (to divide the air supply into several streams)
- 4 gallons of water
- 3+ feet of aquarium hose
- unsulfured molasses
Attach 3 separate pieces of hose at least 12″ long to the gang valve.
Place the gang valve onto the bucket and make sure the hoses reach the bottom of the bucket. Weigh down the ends of the hoses with weights or small rocks taped or wired to the end of the hoses so that they remain at the bottom of the bucket.
Add the finished mature compost and ensure the hoses' ends are covered. Add the water, filling the bucket to within 6 inches of the top.
(NOTE: If using water from a public water source, run the pump and bubble air through the water for at least an hour before adding the water to the compost. This allows any chlorine to evaporate. Chlorine can kill beneficial organisms in the tea).
Add 1 ounce of unsulfured molasses to provide a food source for the beneficial microorganisms. Turn on the aquarium pump and let the mixture brew for 2 to 3 days. Stir the brew occasionally to help mix the compost and separate the microorganisms from the solid compost particles.
After brewing the mixture, strain the tea. Use cheesecloth and strain the tea/compost mixture into another bucket. (Put the compost solids back into the compost pile or in the garden).
The tea should smell sweet and earthy. If it smells bad, do not use it on the plants, but dump the mixture back into the compost pile.
Apply the compost tea to the plants immediately. The beneficial microbes will begin to die shortly after the air source is removed. Sprinkle the compost tea onto the foliage and the soil around each plant.
The tea will provide nutrients and an energy boost to the plants. Apply compost tea every two weeks to the garden.
Mixing Growing Medium (soil)
There are many commercially available soil mixes online or at a local grow supply stores that have been specifically developed for growing cannabis both indoors and outdoors.
For the experienced grower who chooses to mix their own soil, consider using this as a starting point for creating cannabis grow medium (soil):
- 50% Premium Potting Soil
- 20% Bat Guano High Phosphate Fertilizer
- 10% Organic Seafood Fertilizer
- 10% Perlite
- 05% Sand (optional)
- 05% Organic Mix roots, bark, etc.
Add more if a deficiency occurs in flowering. It is highly doubtful that it will, but if it does, use a diluted foliar feed.
- 3 lbs. Bone Meal
- 1 cup Dolomite Lime
- 2 tbsp. Humic acids are highly recommended.
Apply as recommended per the manufacturer's instructions.
- 5 lbs. Bat guano
- 2 five-gallon scoops of Perlite
It is recommended that all the ingredients be mixed together in a large barrel with a tight fitting lid, so as not to breathe in any dust or particles.
Roll the barrel around to mix the ingredients. If mixing the grow medium without a barrel with a lid and instead mixing the ingredients in an open container, a particle or dust mask must be worn.
Slightly moisten the ingredients to help avoid creating too much airborne dust and particles as the ingredients are mixed.
Some of the leading brands of cannabis nutrients are:
These are some of the best cannabis nutrients on the market today.
Start You Garden Today with Online Cannabis Training
Starting an indoor or outdoor cannabis garden can be a rewarding and fulfilling experience, but it is important to have a solid understanding of the plant's specific nutrient requirements. By enrolling at Cannabis Training University (CTU), you will gain the knowledge and skills needed to successfully grow your own cannabis.
CTU offers a wide range of courses for individuals of all experience levels, from beginner to advanced. Whether you are interested in growing cannabis for personal use or for a commercial operation, CTU's comprehensive curriculum will provide you with the training and resources you need to be successful.
To learn how to grow robust, healthy cannabis plants from seed to harvest, enroll in Cannabis Training University's marijuana courses.
Luis Cordova is a distinguished author, and renowned expert in cannabis cultivation, who possesses a Master's degree in Plant Biotechnology and Pharmaceutical Science. As a valued contributor to highly esteemed publications such as Cannabis Training University and Maximum Yield Magazine, Luis has emerged as a trusted source of guidance and knowledge in the cannabis industry. Having written thousands of informative articles, Luis is widely recognized for his comprehensive expertise on cultivating cannabis, both indoors and outdoors.