Cannabis Nutrient Disorders

CANNABIS NUTRIENT DISORDERS

Nutrient disorders are caused by too much or too little of one or several nutrients being available. 

These nutrients are made available between a pH range of five and seven (5-7) and a total dissolved solids (TDS) range from (800 -3000 PPM) (parts per million).  Maintaining these conditions is the key to proper nutrient uptake.

Too much of a nutrient may cause toxicity.  Symptoms of toxicity often mimic symptoms of deficiency.

Nutrients:  Over twenty elements are necessary for a plant to grow.  Carbon, hydrogen and oxygen are absorbed from the air and water.  The rest of the elements, called mineral nutrients, are dissolved in the nutrient solution.  The primary or macronutrients (nitrogen (N), phosphorus (P) and potassium (K)) are the elements plants use the most.  Calcium (Ca) and magnesium (Mg) are secondary nutrients and used in smaller amounts.  Iron (Fe), sulfur (S), manganese (Mn), boron (B), molybdenum (Mo), zinc (Zn) and copper (Cu) are micronutrients or trace elements.  Trace elements are found in most soils.  Rockwool (hydroponic) fertilizers must contain these trace elements, as they do not normally exist in sufficient quantities in Rockwool or water.  Other elements also play a part in plant growth.  Aluminum, chlorine, cobalt, iodine, selenium, silicon, sodium and vanadium are not normally included in nutrient mixes.  They are required in very minute amounts that are usually present as impurities in the water supply or mixed along with other nutrients.

*NOTE: The nutrients must be soluble (able to be dissolved in water) and go into solution. Useless otherwise.

Macronutrients are those plants use a lot of while micronutrients are needed in much smaller amounts by plants.

Macronutrients:   Nitrogen (N) is primary to plant growth.  Nitrogen is the most common deficiency in cannabis.  Nitrogen deficiency shifts sex ratios towards male plants.  Nitrogen deficiency is common in loose, sandy soils.  Excess nitrogen causes lush, dark green growth, susceptible to insects and diseases.  Roots of nitrogen-overdosed plants discolor and rot.  Plants convert nitrogen to make proteins essential to new cell growth.  Nitrogen is mainly responsible for leaf and stem growth as well as overall size and vigor.  Nitrogen moves easily to active young buds, shoots and leaves and slower to older leaves.  Deficiency signs show first in older leaves.  They turn a pale yellow and may die.  New growth becomes weak and spindly.  An abundance of nitrogen will cause soft, weak growth, even delay flower, and fruit production if it is allowed to accumulate.

Phosphorus (P) is necessary for photosynthesis and works as a catalyst for energy transfer within the plant.  Excess phosphorus reduces the availability of zinc, iron, magnesium, and calcium in new leaves.  Phosphorus helps build strong roots and is vital for flower and seed production.  Highest levels of phosphorus are used during germination, seedling growth and flowering.  Deficiencies will show in older leaves first.  Leaves turn deep green on a uniformly smaller, stunted plant.  Leaves show brown or purple spots.

NOTE: Phosphorus flocculates (gets lumpy) when concentrated and combined with calcium.

Potassium (K) activates the manufacture and movement of sugars and starches, as well as growth by cell division.  Potassium leaches easily (deficiencies arise in sandy soils).  Excesses may lead to deficiencies of calcium or magnesium.  Potassium increases chlorophyll in foliage and helps regulate stomata openings so plants make better use of light and air.  Potassium encourages strong root growth, water uptake and triggers enzymes that fight disease.  Potassium is necessary during all stages of growth.  It is especially important in the development of fruit.  Deficiency signs of potassium:  plants are the tallest and appear healthy.  Older leaves mottle and yellow between veins, followed by whole leaves that turn dark yellow and die.  Flower and fruit drop are common problems associated with potassium deficiency.  Potassium is usually locked out by high salinity.

Secondary Nutrients:  Magnesium (Mg) is a central atom in the chlorophyll molecule and is essential to the absorption of light energy.  Co-factor in production of ATP.  Magnesium aids in the utilization of nutrients, neutralizes acids and toxic compounds produced by the plant.  Deficiency signs of magnesium:  Older leaves yellow from the center outward, while veins remain green on deficient plants.  Leaf tips and edges may discolor and curl upward.  Growing tips turn lime green if the deficiency progresses to the top of the plant.

Calcium (Ca) is fundamental to cell manufacture and growth.  Part of cell walls.  Regulates cell wall construction.  Enhances uptake of negatively charged ions.  Soil gardeners use dolomite lime, which contains calcium and magnesium, to keep the soil sweet or buffered.  Rockwool gardeners use calcium to buffer excess nutrients.  Calcium moves slowly within the plant and tends to concentrate in roots and older growth.  Consequently, young growth shows deficiency signs first.  Deficient leaf tips, edges and new growth will turn brown and die back.  If too much calcium is applied early in life, it will stunt growth as well.  It will also flocculate (clump) when a concentrated form is combined with potassium.

Trace Elements:  Sulfur (S) is a component of plant proteins and plays a role in root growth and chlorophyll supply. Enzyme activator.   Distributed evenly with the largest amounts in leaves (affects the flavor and odor in many plants).  Symptoms of sulfur shortage resemble nitrogen deficiency—chlorosis of leaves.  Sulfur, like calcium, moves little within plant tissue and the first signs of a deficiency are pale young leaves.  Growth is slow but leaves tend to get brittle and stay narrower than normal.

Iron (Fe) is a key catalyst in chlorophyll production and is used in photosynthesis.  Component in many enzymes.  Young leaves deficient in iron develop interveinal chlorosis with green veins (like symptoms of Mn deficiency).  A lack of iron turns leaves pale yellow or white while the veins remain green.  Iron is difficult for plants to absorb and moves slowly within the plant. Adding an acidifying agent to the soil improves Fe availability.  Always use chelated (immediately available to the plant) iron in nutrient mixes.

Manganese (Mn) works with plant enzymes to reduce nitrates before producing proteins. A co-factor in many plant reactions.  Essential     for chloroplast production.   A lack of manganese turns young leaves a mottled yellow or brown.   Excess Mn arises in acidic soils and soils that have been steam sterilized.  Overdosing Mn locks up Zn and iron.  Mn may play a role in cannabinoid synthesis.

Zinc (Zn) (micronutrient) is a catalyst and must be present in minute amounts for plant growth. Component of many enzymes.  Essential for plant hormone balance,   Zinc causes the most problems in cannabis.  A lack of zinc results in stunting, yellowing and curling of small leaves.  An excess of zinc is uncommon but very toxic and causes wilting or death.

Copper (Cu) is a catalyst for several enzymes.  A shortage of copper makes new growth wilt and

causes irregular growth.  An excess of copper causes sudden death.  Excess Cu results in Fe deficiency, especially in acid soils. Component of enzymes involved with photosynthesis.   Copper is also used as a fungicide and wards off insects and diseases because of this property.  Toxicity may arise from repeated use of copper sulfate fungicides.

Boron (B) is necessary for cells to divide and protein formation.  It also plays an active role in

pollination and seed production. Shortages cause grey specks on leaves, or chlorosis, with twisted growth.  Terminal buds turn brown or grey and then die, lateral buds follow suit.  Boron shortages arise in marshland soils.  Important in sugar transport within plant.  Role in cell division.  Required for production of certain amino acids.

Molybdenum (Mo) helps form proteins and aids the plant's ability to fix nitrogen from the air.  A

deficiency causes “whiptail disease” – young leaves grow pale, twisted, and withered.  Irregular leaf growth may also result. Excess Mo, causes iron and copper deficiency (not common).  Reduces absorbed nitrates into ammonia prior to incorporation into amino acids.  Essential for nitrogen fixation by nitrogen-fixing bacteria.

Chloride (Cl) shortage causes wilting and chlorosis or bronzing of leaves.  Excess does the same thing.  Used for regulating turgor.  Keeps plant cells free of infection by disease organisms.

Selenium (Se) Plants do not require it, but we do.  Plants absorb it from the soil (so it should be in your soil).  In general, soils in rainier areas have less Se (Pacific Northwest).

These nutrients are mixed together to form a complete plant fertilizer.  The mix contains all the

nutrients in the proper ratios to give plants all they need for lush, rapid growth.  Fertilizer is

dissolved in water to make a nutrient solution.  Water transports these soluble nutrients into contact with the plant roots.  In the presence of oxygen and water, the nutrients are absorbed through the root hairs.

Calcium as a nutrient plays an important role in crop health and quality.  Of particular interest to cannabis producers is calcium’s action in strengthening cell structure. Enhances uptake of negatively charged ions (nitrate, sulfate, borate, molybdate).  Balances charged particles (cations, ions) produced by plant.

Total soil balance requires not only a balance of “base” cations (calcium, magnesium, and potassium), but also a balance of anions, particularly phosphates and sulfates.

Efficiency of carbon cycling is ultimately dependent on phosphorus.  Rock phosphates are the least expensive source of phosphate, but also supply about twenty-four percent (24%) calcium and a range of micronutrients (particularly molybdenum) as well.

Sulfur is essential for enthusiastic microbial activity.  Most microbes need one part of sulfur for each ten parts of nitrogen and phosphorus.  What is commonly described as the carbon: nitrogen ratio (C:  N) is really the carbon:  nitrogen:  phosphorus:  sulfur ratio and should be about 250:10:10:1 for optimal microbial health.  The second important role for sulfur is its significant influence on protein quality.  Enzyme activator and co-enzyme.   Part of all proteins.  Sufficient sulfur provided by adding gypsum or potassium sulfate.

It is not wise to attempt micronutrient correction of a soil.  Most micronutrients are very expensive, and several are toxic if too much is added.

Cannabis is nutrient hog.  It requires even more nutrients than an equivalent crop of maize.

Agronomically ideal recipe for a field crop of cannabis:   One ton of 10-10-10

360 kg.  ammonium sulfate

200 kg.  Mono-ammonium phosphate

110 kg.  sulfate of potash-magnesia

90 kg.  fertilizer grade gypsum

80 kg.  potassium chloride (muriate)

55 kg.  potassium sulfate

50 kg.  sodium-calcium borate

15 kg.  magnesium oxide

14 kg.  manganese sulfate

14 kg.  zinc sulfate

12 kg.  copper sulfate

Fertilizing glass houses and grow room soils.  Three (3) soil mixtures:

1. 
   5 parts soil/2 parts perlite/1 part composted manure
2. 
   5 parts soil/1 part sand/1 part peat/half part blood meal/half part wood ash
3. 
   5 parts soil/1 part vermiculite/1 part sand/1 part peat/quarter part 12-12-12 chemical fertilizer

Organic matter must be added to your soil.  It improves all soils!  Particles of organic material have negatively charged surfaces, which keep K, Mg, Ca, and other positively charged cations from leaching out of soil.  Organic material brings soil to life by providing nutrients for saprophytic microorganisms.  Soil should consist of between four and ten (4-10%) organic material.  Organic matter must be added to soil every year, since soil microorganisms break it down.

It is better to supplement with organic fertilizers rather than chemical fertilizers.  Organic fertilizers (composted manures), improve soil texture and nurture soil microorganisms.  Chemical fertilizers harm soil texture and kill soil organisms.  Organically grown plants contain seventy nine percent (79%) more THC than inorganically grown cannabis.  Organic crops cause less laryngitis in smokers than chemically fertilized crops.

Not all organic fertilizers are safe.  Do not spray marijuana plants with fish emulsion—virtually all liquid foliar fertilizers, including fish emulsion, contain nitrates.  Leaves of cannabis convert nitrates into carcinogenic N-nitrosamines.

Macronutrient deficiencies should be corrected with a mix of rapidly absorbed fertilizers and slow release fertilizers.

Micronutrient supplementation is tricky.  They are easily over-supplemented, causing toxicity.  Composted manure contains adequate micronutrients.  Maintaining organic matter and proper soil pH is usually sufficient for most micronutrients.

The pH of soil affects the availability of soil nutrients.  In humid areas, soil acidity increases to the point that many nutrients become unavailable.  Acid soils need to be limed.  Limestone (calcium carbonate, CaCO3) is a cheap way to neutralize acid soils.

Cannabis does not tolerate excess salt (NaCl), or saline/brackish water.  Many air pollutants are injurious to plants.  Injury peaks during daylight hours, and worsens in warm, humid conditions.  “Acid rain” doubles the damage by acidifying soil and creating various nutrient deficiencies.  The lowest rain pH reported (pH 1.7 in Los Angeles) was more acidic than vinegar (pH 3.0).  Sulfur dioxide gas (SO2) causes chlorosis in cannabis.  Combined with water it forms toxic droplets of acid rain.  Hydrogen fluoride gas (HF) causes necrosis of leaf tips and margins.  Young growth is most susceptible, especially when wet.  Various industries and factories processing ore or oil produce HF vapors.  Nitrogen dioxide gas (NO2 causes symptoms similar to SO2 toxicity.  NO2 combines with O2 in bright sunlight to form ozone.  Ozone (O3) is the most destructive air pollutant to plants.  Chlorotic spots appear, enlarge, and turn brown, leaves defoliate prematurely and plants become severely stunted.  Ozone binds with incompletely combusted gasoline to produce peroxyacyl nitrates (smog).  Automobiles, industries, and burning rainforests produce carbon dioxide (CO2).  Global levels of CO2 are rising.  This may promote photosynthesis, and plant growth.  However, it dilutes the plant’s nitrogen concentration, which forces insects and other nitrogen seeking herbivores to eat more plant tissue.  Increased CO2 also exacerbates weed problems.

Cannabis absorbs many heavy metals from the soil without ill effects.  Ingesting plants laced with lead (contaminant found in chemical fertilizers) causes anemia and brain damage.  Ingesting mercury, another cumulative toxin, also causes neurologic deficits.  Volcanoes and coal release Mercury.  Cannabis grown in Hawaiian soil is much worse for us.  Smoking 100 g. of volcanic marijuana per week would lead to mercury poisoning.  Cannabis absorbs heavy metals that are in the soil where it is grown.  .  Cannabis grown near uranium mines or gold mines will be loaded with these metals.

Some of the most dangerous toxins are agricultural pesticides.  Many insecticides, miticides and fungicides are phytotoxic.

Farmers apply tons of herbicides to their fields, and tons of herbicides move off target by vapor drift and water runoff.  Cannabis is very sensitive to herbicide drift.

Do not forget; stop fertilizing at least fourteen (14) days before you intend to harvest your plants.  Water with clean, pure water.  This will improve the taste and flavor, the burn, and it will be better for your health.

Solutions to Nutrient Deficiencies

The Nutrients:

Nitrogen - Plants need lots of N during vegging, but it is easy to overdo it.  Added too much?  Flush the soil with plain water.  Soluble nitrogen (especially nitrate) is the form that is the most quickly available to the roots, while insoluble N (like urea) first needs to be broken down by microbes in the soil before the roots can absorb it.  Avoid excessive ammonium nitrogen, which can interfere with other nutrients.  Too much N delays flowering.  Plants should become N-deficient late in flowering for best flavor.

Magnesium ( Mg) deficiency is common since cannabis uses lots of it and many fertilizers do not have enough of it.  Mg deficiency is easily fixed with ¼ teaspoon/gallon of Epsom salts (first powdered and dissolved in some hot water) or foliar feed at ½ teaspoon/quart.  When mixing up soil, use two teaspoons dolomite lime per gallon of soil for Mg.  Too much Ca, Cl or (ammonium) nitrogen can lock up Mg.  Do not overdo Mg or you will lock up other nutrients.

Potassium - Too much sodium (Na) displaces K, causing a K deficiency.  Sources of high salinity are baking soda (sodium bicarbonate "pH-up"), too much manure, and the use of water-softening filters (which should not be used).  If the problem is Na, flush the soil.  K can be locked up from too much Ca or ammonium nitrogen, and possibly cold weather.

Phosphorous - Some deficiency during flowering is normal, but too much should not be tolerated.  Red petioles and stems are a normal, genetic characteristic for many varieties, plus it can also be a co-symptom of N, K, and Mg-deficiencies, so red stems are not a foolproof sign of P-deficiency.  Too much P can lead to iron deficiency.

Iron - Fe is unavailable to plants when the pH of the water or soil is too high.  If deficient, lower the pH to about 6.5 (for Rockwool, about 5.7), and check that you are not adding too much P, which can lock up Fe.  Use iron that is chelated for maximum availability.  Read your fertilizer's ingredients - chelated iron might read something like "iron EDTA".  Too much Fe without adding enough P can cause a P-deficiency.

Manganese - Mn is locked out when the pH is too high, and when there is too much iron.  Use

chelated Mn.

Zinc - Also is locked out due to high pH.  Zn, Fe, and Mn deficiencies often occur together, and are usually from a high pH.  Do not overdo the micronutrients.  Lower the pH if that is the problem so the

nutrients become available.  Foliar feed if the plant looks stressed.  Use chelated zinc.

Check Your Water - Crusty faucets and showerheads mean your water is "hard”, usually due to too

many minerals.  Tap water with a TDS (total dissolved solids) level of more than around 200ppm (parts

per million) is "hard" and should be looked into, especially if your plants have a chronic problem.  Ask

your water company for an analysis listing, which will usually list the pH, TDS, and mineral levels (as

well as the pollutants, carcinogens, etc) for the tap water in your area.  This is a common request,

especially currently, so it should not raise any red flags.  Regular water filters will not reduce a

high TDS level, but the costlier reverse-osmosis units, distillers, and de-ionizers will.  A digital TDS

meter (or EC = electrical conductivity meter) is an incredibly useful tool for monitoring the nutrient

levels of nutrient solution, and will pay for itself before you know it.

General Feeding Tips – Cannabis plants are very adaptable, but a general rule of thumb is to use more

nitrogen and less phosphorous during the vegetative period, and the exact opposite during the flowering

period.  For the vegetative period try an N:  P:  K ratio of about 10:7:8 (which is the same ratio as

20:14:16).  For flowering plants, 4:8:8.  Check the pH after adding nutrients.  If you use a reservoir,

keep it circulating and change it every 2 weeks.  A general guideline for TDS levels is as follows: 

seedlings = 50-150 ppm; unrooted clones = 100-350 ppm; small plants =400-800 ppm; large plants =

900-1800 ppm; last week of flowering = taper off to plain water.  These numbers are just a guideline, and

many factors can change the actual level the plants will need.  Certain nutrients are "invisible" to TDS

meters, especially organics, so use TDS level only as an estimate of actual nutrient levels.  When in

doubt about a new fertilizer, follow the fertilizer's directions for feeding tomatoes.  Grow a few tomato or

radish plants nearby for comparison.

PH - The pH of water after adding any nutrients should be around 5.9-6.5, (in Rockwool, 5.5-6.1).

pH Scale  { 1  2  3  4  5  6  7  8  9  10  11  12  13  14}  7 neutral,  1 most acid,  14 most alkaline

Generally ,  the micro-nutrients (Fe, Zn, Mn, Cu) get locked out at a high pH (alkaline) above 7.0,  while the major nutrients (N, P, K, Mg) can be less available in acidic soil or water (below 5.0).  Tap water is often too alkaline.  Soils with lots of peat or other organic matter in them tend to get too acidic.  Add some dolomite

lime.  It is a good idea to get a “good” soil test kit.  Also good to get a pH (color based) test kit.  Invest in a digital pH meter ($40-$80), preferably a waterproof one.

Cold weather (below 50 degrees F./10 degrees C.) can lock up phosphorous.  Some varieties (equatorial sativas) do not do well in cold weather.  If you can keep the roots warmer, the plant will be able to take cooler temperatures than it otherwise could.

If the lights are too close to the plant, the tops may get curled, dry, and looked burnt (because they are).

This can look like a nutrient problem.  Your hand should not feel hot after a minute when you

hold it at the top of the plants.  Raise the lights and/or aim a fan at the hot zone.  Room temperature best less than 85 degrees F.  Alternatively (29 degrees C.), or 90 degrees F. or (33 degrees C.) if you have extra CO2. 

Humidity - Thin, shriveled leaves can come from low humidity.  Forty to eighty percent is usually okay.

Mold and fungus - Dark patchy areas on leaves and buds can be mold.  Lower the humidity and

increase the ventilation if mold is a problem.  Remove any dead leaves, wherever they are.  Keep your

garden clean.

Insects - White spots on the tops of leaves can mean spider mites hiding underneath

Sprays - Foliar sprays can have a "magnifying glass" effect under bright lights causing small white,

yellow or burnt spots that can be confused with a nutrient problem.  Some sprays can also cause

chemical reactions.

Insufficient light -- tall, stretching plants are usually from using the wrong kind of light.  Do not use

regular incandescent bulbs ("grow bulbs") or halogens to grow cannabis.  Invest in fluorescent lighting

(good) or HID lighting (much better) which supply the high-intensity light that cannabis needs for

good growth and tight buds.  Even better, grow in sunlight.

Clones - yellowing leaves on unrooted clones can be from too much light, or the stem may not be firmly touching the rooting medium.  Turn off any CO2 until they root.  Too much fertilizer can shrivel, wilt, or kill clones.  Plain tap water (with Olivia’s in it) is perfect.

Video on nutrient deficiencies:

www.videos.lalibre.be/video/iLyROoafY4kK.html

www.youtube.com/watch?v=DzcSA39im1g

www.youtube.com/watch?v=XpphmpzoQqM

Symptoms of Nutrient Deficiencies

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