Categories
BLOG

nitrogen deficiency weed

How To Prevent And Fix Every Cannabis Nutrient Deficiency

Cannabis plants require a varied and healthy diet to put out the best yields possible. Use this guide to prevent nutrient deficiencies and quickly fix them if they arise.

Nutrient deficiencies: How to prevent and fix them.

  • 1. Macro vs micronutrients
  • 2. Mobile vs immobile nutrients
  • 3. pH matters
  • 4. Going organic
  • 5. How to prevent and solve nutrient deficiencies
  • 6. Nitrogen
  • 7. Phosphorous
  • 8. Potassium
  • 9. Calcium
  • 10. Sulphur
  • 11. Magnesium
  • 12. Iron
  • 13. Manganese
  • 14. Boron
  • 15. Molybdenum
  • 16. Zinc
  • 1. Macro vs micronutrients
  • 2. Mobile vs immobile nutrients
  • 3. pH matters
  • 4. Going organic
  • 5. How to prevent and solve nutrient deficiencies
  • 6. Nitrogen
  • 7. Phosphorous
  • 8. Potassium
  • 9. Calcium
  • 10. Sulphur
  • 11. Magnesium
  • 12. Iron
  • 13. Manganese
  • 14. Boron
  • 15. Molybdenum
  • 16. Zinc

Just like us, cannabis plants require a varied and healthy diet to survive and thrive. They need the right amount of nutrients to fulfil important physiological functions, and if they lack just one piece of the puzzle, growth will slow down and yields may be affected.

Luckily, the cannabis plant does a pretty good job of communicating what it needs. If nutrient deficiency strikes, it often sends out a signal—wilting, discolouration, curled leaves—to inform the cultivator of what it requires.

Before we dive into how to prevent and fix each nutrient deficiency, they are a few important things you should know.

MACRO VS MICRONUTRIENTS

Macronutrients are minerals that cannabis plants require in large amounts. These include nitrogen, phosphorus, and potassium. Just like fats, carbs, and protein form the cornerstone of the human diet, cannabis needs these important minerals in large quantities to carry out key processes.

Micronutrients are minerals and elements required in much smaller amounts. However, they are just as vital to plant health. These include iron, zinc, sulphur, boron, and others. Think of them like minerals and vitamins in the human diet. We don’t need much of them, but without them, it wouldn’t take long to fall ill.

MOBILE VS IMMOBILE NUTRIENTS

Learning the difference between mobile and immobile nutrients can help growers diagnose deficiencies more accurately.

Mobile nutrients are minerals that can be shuttled throughout the plant to areas that need them the most. For example, phosphorus stored in older fan leaves can be directed towards newer growth if a deficiency occurs. Therefore, deficiency of a mobile nutrient will first become noticeable in older growth.

Immobile nutrients remain locked in place and plants cannot redistribute them. For example, if a zinc deficiency takes hold, the signs will first show in the newer growth as the plant can’t relocate its mineral stash.

NUTRIENT DEFICIENCY
(Old leaves)

MOBILE VS IMMOBILE NUTRIENTS
ELEMENT (Symbol) MOBILITY IN PLANT NUTRIENT DEFICIENCY
(Old leaves)
NUTRIENT DEFICIENCY
(New leaves)
Nitrogen (N) Mobile X
Phosphorous (P) Mobile X
Potassium (K) Mobile X
Calcium (Ca) Immobile X
Sulfur (S) Immobile X
Magnesium (Mg) Mobile X
Iron (Fe) Immobile X
Manganese (Mn) Immobile X
Boron (B) Immobile X
Molybdenum (Mo) Immobile X
Zinc (Zn) Immobile X

PH MATTERS

Your soil can hold all of the nutrients your plant needs, but it won’t be able to access them if the pH is off. Cannabis plants thrive in a soil pH of between 6.0–6.5. Any lower or higher and plant roots will struggle to absorb key nutrients—a phenomenon known as nutrient lockout. Routine flushes can prevent this from happening. Keep an eye on your values using a pH meter. You can also change the pH of your soil using these techniques.

GOING ORGANIC

Advances in soil science have shown that the rhizosphere (root zone) is beaming with life. Here, a complex network of microorganisms works synergistically with the root system. The soil needs an optimal balance of bacteria and fungi to break down organic matter and free up nutrients for plants to use.

Focusing on composting and building living soil provides long-term prevention of nutrient deficiencies and supports thriving biodiversity within the rhizosphere. Such beneficial life will help your yields soar.

However, growers can take more direct action in the short-term. Foliar spraying can be administered as a quick fix when plants are missing out on some nutrients. These feeds bypass the roots and are absorbed straight through the leaves.

HOW TO PREVENT AND SOLVE NUTRIENT DEFICIENCIES

Below is a list of key nutrient deficiencies that may arise, as well as how to prevent them and fix them if they strike.

NITROGEN

A mobile macronutrient, nitrogen plays a major role in photosynthesis and the formation of vital plant proteins. Nitrogen deficiency can result in yellowing older leaves, older leaves dropping off, eventual discolouration of the entire plant, and reduced yields.

• Keep pH within an optimal range (6.0–6.5).
• Start off with a nutrient-dense potting mix.
• Start composting to ensure a nutrient-dense medium in the future.
• Mycorrhizae are associated with nitrogen-fixing bacteria. Add them to your soil to boost nitrogen levels.

• The majority of organic fertilisers contain enough nitrogen to fix the deficiency: Try fish meal, manure, alfalfa, or feather meal.
• Adjust pH accordingly.
• Apply compost tea as a foliar spray for a fast-acting solution.
• Increase the amount of nitrogen in your compost using kitchen scraps, fresh prunings, and grass clippings.

PHOSPHORUS

Phosphorus also acts as a macronutrient in the cannabis plant. Being a mobile nutrient, plants can direct the mineral to the areas that need it most. Phosphorus plays an essential role in photosynthesis and protein synthesis, and it’s a crucial component of DNA. Phosphorus deficiency can manifest as red/purple stems, brown spots on leaves, and dry leaves.

• Utilise soil high in organic matter.
• Increase the absorption rate by using well-aerated soil.
• Use mycorrhizal fungi in your soil to improve phosphorus uptake. These microbes help to turn insoluble phosphates into available molecules.
• Add more manure to your compost.

• Nudge pH up to the higher end of the spectrum—your plant will have an easier time absorbing it.
• Add worm castings and fish meal to your soil.
• Apply an organic fertiliser high in phosphate.
• You may be overwatering. Only water when the top 3cm of soil is dry to avoid making the medium overly compact.
• Move your plants to a warmer location or erect a tarp to trap heat. Plants find it harder to uptake phosphorus in temperatures below 15°C.

POTASSIUM

Potassium: the third and final macronutrient. It helps to regulate CO₂ uptake and plays a role in photosynthesis. The mobile nutrient also helps in the production of ATP (the cellular unit of energy). Potassium deficiency appears as brown and yellow leaf tips and edges, curled-up leaves, and stretching.

• Be careful when using fertilisers. Feeding your plant too often can cause salt to build up and interrupt potassium uptake.
• Bolster your compost with hardwood ash and kelp meal.
• Don’t overwater.

• Flush the medium.
• Measure and adjust pH to correct possible nutrient lockout.
• Add chicken manure to the soil.
• Apply organic seaweed as a foliar spray.

CALCIUM

Critical to plant health, this immobile micronutrient helps to hold plant cell walls together. Calcium deficiency can lead to new growth—root tips and young leaves—forming incorrectly and becoming warped.

• Add dolomitic lime/garden lime to the growing medium.
• A pH of 6.2 provides the best environment for calcium uptake.
• Add plenty of eggshells to your organic compost.
• Keep a worm farm! Worm castings provide loads of nutrients, including calcium.

• Apply a cal-mag supplement.
• Increase or decrease pH towards 6.2.
• Add one teaspoon of hydrated lime to 4l of water and use the solution to water your plants.

SULPHUR

Although required in very small amounts, this key immobile nutrient contributes to forming vital enzymes and proteins. A sulphur deficiency will lead to yellowing of new growth and discoloration on the undersides of leaves.

• Bolster your compost pile with manure.
• Fungi and bacteria are key for releasing sulfur in the soil. Employ techniques such as no-till to encourage them and add some mycorrhizae if you’re growing in pots.

• Epsom salts are rich in sulphur. Add 1–2 teaspoons of Epsom salts to about 4l of water and supplement until symptoms disappear.
• Adjust pH to the optimal range if needed.

MAGNESIUM

Without this mobile micronutrient, photosynthesis would not be possible. The mineral sits at the heart of the chlorophyll molecule and enables it to absorb light. Magnesium deficiency will result in lower growth looking worse for wear. Leaves will become yellow, dry out, and eventually turn brown.

• Include dolomitic limestone in the growing medium.
• Use compost rich in manure.
• Maintain good pH balance.

• Flush the medium with 6.0 pH water if pH is out of balance.
• Epsom salts also provide magnesium. Add 1–2 teaspoons of Epsom salts to about 4l of water and apply until symptoms resolve.

Iron plays an essential role in chlorophyll formation. The element also forms part of several enzymes and some important pigments. Overall, this immobile micronutrient helps plants carry out metabolic and energy-forming processes. If your plant experiences iron deficiency, you’ll notice young growth at the top of the plant becoming bright yellow.

• Help your plants absorb existing iron by adding mycorrhizae to the soil. These synergistic organisms help to shuttle the element into the root system and beyond.
• Test your soil pH to rule out nutrient lockout.
• Add chicken manure, kitchen scraps, and seaweed to your compost pile.

• Hit the pH sweet spot.
• Flush the growing medium and add an iron supplement afterwards.
• Use a small amount of nitrogen fertiliser to lower pH and make iron more accessible.

MANGANESE

Manganese doesn’t receive too much attention in the world of cannabis growing. However, this immobile micronutrient plays a fundamental role in cannabis physiology. It aids photosynthesis, respiration, nitrogen assimilation, and root cell elongation, and protects roots from bad microbes.
Manganese deficiency will show up as light green discolouration near the base of new growth. This eventually spans out to the tips, and brown spots begin to emerge.

• Imbalanced pH often underpins manganese deficiency. Frequently measure your soil pH and keep it within the optimal range to ensure your plants can access this mineral.
• Make a manganese-rich compost by adding pineapple, tomatoes, cranberries, and carrots to your pile.

• Flush your containers.
• Prune back any affected growth that doesn’t recover.
• Hit the canopy with a seaweed foliar spray.

BORON

Boron works alongside calcium to give integrity to plant cell walls and help with cell division. Breeders also have a soft spot for this immobile nutrient as it helps with the pollination process. A lack of boron will lead to deficiency symptoms such as a lack of turgor, reduced fertility, poor vegetative growth, and terminated meristems. New growth will become twisted, sugar leaves will wilt, and leaves will show a yellowish-brown discolouration.

• Don’t let plants dry out often.
• Avoid nutrient lockout by NOT overfeeding.
• Don’t let humidity levels drop below 25%.
• Use well-draining, aerated soil.
• Add generous amounts of apples, bananas, broccoli, and chickpeas to your compost pile.

• Flush the medium and aim for an ideal pH range.
• Mix one teaspoon of boric acid in 4l of water and apply to affected plants.

MOLYBDENUM

Another lesser-known nutrient, molybdenum helps to form two essential enzymes that convert nitrate into nitrite and then into ammonia. Plants use the latter to make amino acids, which eventually become proteins. If your plants become deficient in molybdenum, they’ll start to display red and pink discolouration at the edges of new growth. Leaves will also start to become yellow and spotted. Thankfully, molybdenum deficiency is quite rare.

• Keep pH between 6.0–6.5.
• Start your grow with good-quality, living compost.
• Throw the occasional bean, pea, grain, and raw nut onto your compost.

• Flush and adjust pH.
• Spray affected plants with a seaweed foliar spray.
• Water plants with a worm casting compost tea.

Plants don’t need much zinc at all, but illness will strike if they miss out. Zinc forms parts of proteins, membranes, and growth hormones. The immobile micronutrient also regulates enzyme function and stabilises DNA and RNA. What happens when zinc goes missing? Deficiency symptoms manifest in slowed new growth; the distance between nodes lessens, and leaves will look wrinkly and yellow. Eventually, new leaves will display yellowing and rust-coloured tips.

• An excessively alkaline pH causes most zinc deficiencies. Maintain proper pH.
• Boost zinc levels in your compost using pumpkin and squash scraps.
• Good microbes play a large role in zinc uptake—add beneficial fungi to your growing medium

• Reduce alkaline pH to the ideal range.
• Stop overwatering.
• Use a fish or seaweed foliar spray to swiftly boost zinc levels.

Cannabis nutrient deficiencies can slow down your grow and negatively impact yields. Learn how to prevent and cure all of them using this guide.

Nitrogen Deficiency

Problem: A cannabis nitrogen deficiency will cause the older, lower leaves on your plant to turn yellow, wilt away and eventually die. The plant typically appears pale or lime-colored.

The yellow leaves of a nitrogen deficiency may show signs of brown, and they will usually become soft and sort of “fold” in, before possibly turning crispy but ultimately falling off on their own.

Example of cannabis Nitrogen deficiency – yellow bottom leaves. Almost all plant nutrients contain Nitrogen

Nitrogen-deficient plants often appear pale or lime-colored. The leaves on this marijuana plant don’t have obvious leaf symptoms like spots or markings, but they are pale all over the whole plant. Almost lime green. The light-colored leaves are a sign the plant needs more Nitrogen (and nutrients in general). On the flip side, plants that are receiving too much Nitrogen turn dark.

If the yellowing leaves are at the top of your plant or the yellow leaves are mostly new growth, then you probably don’t have a nitrogen deficiency. Nitrogen deficiencies usually affect the oldest, lowest leaves first, or the entire plant becomes light colored.

Nitrogen is a mobile nutrient, which means it can move throughout the plant as needed. Cannabis needs nitrogen to keep leaves green and make energy from light. All new leaves get plenty of nitrogen to make them green and help with photosynthesis. The leaves that get the most light are the newest, youngest leaves, so the plant “wants” to give those leaves priority for getting light.

If new leaves aren’t getting enough nitrogen, the plant will start to “steal” nitrogen from the older, lower leaves, so that it can give it to newer leaves. This is what causes the yellowing and wilting of a nitrogen deficiency.

It’s relatively normal for your cannabis plant’s leaves to start turning yellow towards the end of your flowering cycle as the plant becomes nitrogen deficient while creating buds.

However, if your cannabis plant is losing lower leaves fast due to yellowing (if yellowing and dying leaves is “climbing” up the plant from the bottom), especially in the vegetative stage before plant is making buds, you have a problem that you will need to fix as soon as possible.

You don’t want a nitrogen deficiency in the vegetative stage!

If you notice your lower cannabis leaves turning yellow in the vegetative stage or in the beginning part of the flowering stage, your plant may be experiencing a nitrogen deficiency which will need to be treated.

It is not good if your cannabis plant is showing signs of an advanced nitrogen deificiency while still in the vegetative stage. It’s normal to lose a few yellow leaves off the bottom of your plant here and there, especially with very big plants. But if you are losing a significant amount of yellow leaves, and the yellowing seems to be moving up the plant quickly, then you have a problem.

As a grower, you’re interested in how much nitrogen to give your plants at what time. The ratio of nitrogen to other nutrients has a huge effect on growth and bud formation.

Vegetative Stage – higher levels of Nitrogen (pretty much any plant food will do)

Most complete plant foods that you get at a gardening store contain high levels of nitrogen (N). These nutrient system tend to work well in the vegetative stage.

Some examples of cannabis-friendly one-part Vegetative nutrient systems…

Pretty much any complete plant food

Flowering Stage – lower levels of Nitrogen (use “Bloom” or Cactus nutrients)

It’s extra important to find a nutrient system with lower levels of nitrogen for the last part of your plant’s life. Many “Bloom” or “Flowering” style base nutrients are just the ticket.

Some examples of good one-part Flowering nutrient systems…

If you can’t order online and can’t find a good one-part base Bloom formula locally, you do have other choices. Though not an ideal choice, most Cactus plant foods will contain good nutrient ratios for growing cannabis during the budding stage. So in a pinch, you can use the cactus nutrients that can be found at most gardening stores.

The first cannabis plant pictured below is showing signs of nitrogen deficiency late in flowering; nitrogen deficiency in late flowering is completely normal and even desired. The last picture is an infographic about nitrogen and your marijuana plant.

It’s normal for plants to show signs of a nitrogen deficiency as the plant gets close to harvest. This is actually a good thing! Too much nitrogen can actually prevent proper budding, and can reduce the overall taste and smell of your plant. This is why all “bloom” and flowering nutrient formulas are relatively low in nitrogen.

Don’t worry about yellow leaves close to harvest! It’s normal to see a few Nitrogen-deficient leaves in the flowering stage. Nothing to worry about unless you see the yellowing leaves start climbing up the plant.

So don’t sweat it if you see your cannabis show some signs of nitrogen deficiency late in the flowering stage! Relatively low levels of nitrogen in the late flowering stage help promote proper cannabis bud development and will increase your yields!

Solution: You can find many pre-mixed nutrients from the store which contain nitrogen or you could use nitrate of soda or organic fertilizer which are both good sources of nitrogen. In fact almost all plant nutrients of any kind will include nitrogen. If you haven’t been providing any nutrient to your plants, try supplementing your regular nutrients with a bit more nitrogen and see if the plant starts recovering.

If you’ve already been using nutrients, then you probably don’t have a nitrogen deficiency. If you’re seeing the signs of spreading nitrogen deficiency even a week or two giving nitrogen to your plants through nutrients, then you need to figure out what else is causing the yellowing so you can stop it.

More About Nitrogen and Your Marijuana Plants

Sometimes you can get the signs of a cannabis nitrogen deficiency if the pH at the plant root zone is too low, even if the nitrogen is there. This is because when the pH at the roots is not right, your plant roots can’t properly absorb nutrients. If you aren’t sure about your root pH, learn more about pH & growing cannabis plants here.

Nitrogen is especially important during the vegetative stage of your cannabis plants. As your plants start flowering, they will need lower amounts of nitrogen.

Nitrogen is one of the 3 nutrients that is included in almost every kind of plant food.

When looking at plant nutrients, you’ll almost always see 3 numbers listed, like 3-12-6 or 5-10-5. These numbers represent the percentage of Nitrogen (N), Phosphorous (P) and Potassium (K) contained in the bottle. Just about all plant life on Earth needs these 3 elements to grow.

The 3 numbers on the front of plant nutrient bottles list the amount of Nitrogen, Phosphorus, and Potassium.

The very first number, “3” in the case of the picture to the right, always displays the proportion of nitrogen in this nutrient bottle compared to the other 2 nutrients (Phosphorus and Potassium respectively).

Nitrogen is in all plant nutrient formulations because it’s vital to plant processes.

Note: During the last few weeks before harvest, marijuana plants start pulling all the remaining nitrogen from her leaves as part of the bud-making process. This causes yellowing leaves starting towards the bottom of the plant. This is part of the natural flowering process and you don’t need to fight it. You may notice that marijuana leaves are yellowing in almost all pictures of marijuana plants with big buds that are close to harvest. You tend to get smaller yields from nitrogen-toxic plants with dark green leaves at harvest.

Remember: It’s Normal For Marijuana Leaves To Start Turning Yellow As Harvest Time Approaches

Occassionally a nitrogen toxicity is mistake for a deficiency. Could your plant actually be nitrogen toxic? (pictured below)

This picture shows a Nitrogen Toxicity

Plant Symptoms

  • Bronze or brown patches
  • Brown or slimy roots
  • Brown or yellow leaf tips/edges
  • Buds dying
  • Buds look odd
  • Bugs are visible
  • Curling or clawing leaves
  • Dark leaves
  • Drooping plant
  • Holes in leaves
  • Mold or powder
  • Pink or purple on leaves
  • Red stems
  • Shiny or smooth leaves
  • Spots or markings
  • Twisted growth
  • Webbing
  • Wilting leaves
  • Yellow between leaf veins
  • Yellow leaves

This page is part of our Plant Doctor series. You can use our tool to filter by symptom and help diagnose your plant.

A nitrogen deficiency causes the lower/older leaves of a cannabis plant to start yellowing, wilting, and dropping off on their own. Learn how to fix it.