Secondary Nutrients

The secondary nutrients-magnesium, calcium, and sulfur-are also used by the plants in large amounts. Rapid-growing indoor marijuana crops are able to process more secondary nutrients than most general-purpose fertilizers are able to supply. Many growers opt to use high quality two- and three-part hydroponic fertilizers to supply all necessary secondary and trace elements. But be careful, these three nutrients may be present in high levels in the ground water. It is important to consider these values when adding nutrient supplements. If growing in a soil or soilless mix with a pH below 7 such as Peat-Lite, incorporating one cup of fine (flour) dolomite lime per gallon of medium ensures adequate supplies of calcium and magnesium.

Macronutrients are the elements that the plants use most. The fertilizers usually show nitrogen (N), potassium (P), phosphorous (K) as (N-P-K) percentages in big numbers on the front of the package. They are always listed in the same N-P-K order. These nutrients must always be in an available form to supply marijuana with the building blocks for rapid growtlv

Magnesium (Mg) - mobile

Practical Information: Marijuana uses a lot of magnesium, and deficiencies are common, especially in acidic (pH below 7) soils. Adding dolomite lime to acidic potting soils before planting will stabilize the pH, plus it will add magnesium and calcium to the soil. Add Epsom salts with each watering to correct magnesium deficiencies, if no dolomite was added when planting. Use Epsom salts designed specifically for plants rather than the supermarket-type.

Technical Information: Magnesium is found as a central atom in every chlorophyll molecule, and it is essential to the absorption of light energy, It aids in the utilization of nutrients. Magnesium helps enzymes make carbohydrates and sugars that are later transformed into flowers. It also neutralizes the soil acids and toxic compounds produced by the plant.

Deficiency: Magnesium deficiency is common

indoors. The lower leaves, and later the middle leaves, develop yellow patches between dark, green veins. Rusty-brown spots appear on the leaf margins, tips, and between the veins, as the deficiency progresses. The brownish leaf lips usually curl upward before dying. The entire plant could discolor in a few weeks, and if severe, turn a yellow-whitish tinge before browning and dying. A minor deficiency will cause little or no problem with growth. However, minor deficiencies escalate and cause a diminished harvest as flowering progresses. Most often, magnesium is in the soil but is unavailable to the plant because the root environment is too wet and cold or acidic and cold. Magnesium is also bound in the soil if there is an excess of potassium, ammonia (nitrogen), and calcium (carbonate). Small root systems are also unable to take in enough magnesium to supply heavy demand. A high EC slows the water evaporation and will also diminish magnesium availability.

Progression of deficiency symptoms at a glance:

No deficiency symptoms are visible during the first three to four weeks.

In the 4"' to the 6th week of growth, the first signs of deficiency appear, tnterveinal yellowing and irregular rust-brown spots appear on older and middle-aged leaves. Younger leaves remain healthy,

Leaf tips turn brown and curl upward as the deficiency progresses.

Early stage of Mg deficiency.

Progression of Mg deficiency.

Later stage of Mg deficiency.

Rust-brown spots multiply and interveinal yellowing increases.

Rust-brown spots and yellowing progress, starting at the bottom and advancing to the top of the entire plant.

Younger leaves develop rust-colored spots and interveinal yellowing.

The leaves dry and die in extreme cases.

Treat deficiency by watering with two teaspoons of Epsom salts (magnesium sulfate) per gallon of water. For fast results, spray the foliage with a 2 percent solution of Epsom salts. If the deficiency progresses to the top of the plant, it will turn green there first. In four to six days, it will start moving down the plant, turning lower leaves progressively more green. Continue a regular watering schedule with Epsom salts until the symptoms totally disappear. Adding Epsom salts regularly is not necessary when the fertilizer contains available magnesium. Use a foliar spray of Epsom salts for a fast cure. Another option is to apply magnesium sulfate monohy-drale in place of Epsom salts. Add fine dolomite lime to soil and soilless mix to add a consistent supply of both calcium and magnesium over the long term. Always use the finest dolomite available.

Control the room and root-zone temperatures, humidity, pl-l, and EC of the nutrient solution. Keep root zone and nutrient solution at 70 to 75°F (21-24°C). Keep ambient air temperature at 75°F (21°C) day and 65°F (18°C) night. Use a complete fertilizer with an adequate amount of magnesium. Keep the soil pH above 6.5, the hydroponic pH above 5.5, and reduce high EC for a week.

The extra magnesium in the soil is generally not harmful, but it can inhibit calcium uptake. Signs of excess magnesium are described below.

Toxicity: Magnesium toxicity is rare and difficult to discern with the naked eye. If extremely toxic, the magnesium develops a conflict with other fertilizer ions, usually calcium, especially in hydroponic nutrient solutions. The toxic buildup of magnesium in soil that is able to grow marijuana is uncommon, Calcium (Ca) - immobile

Practical Information: Cannabis requires nearly as much calcium as other macronutrients. Avert deficiencies in the soil and in most soilless mixes by adding fine dolomite lime or using soluble-hydroponic fertilizers containing adequate calcium.

Technical Information: Calcium is fundamental to cell manufacturing and growth. Calcium is necessary to preserve membrane permeability and cell integrity, which ensures proper flow of nitrogen and sugars. It stimulates enzymes that help build strong cell and root walls. Cannabis must have some calcium at the growing tip of each root.

Deficiency of calcium is somewhat uncommon indoors, but not uncommon in fiber hemp. Frequently, plants can process more calcium than is available. It also washes out of the leaves that are sprayed with water. Deficiency signs may be difficult to detect. They start with weak stems, very dark green foliage, and exceptionally stow growth. Young leaves are affected, and they show the signs first. Severe calcium deficiency causes new, growing shoots to develop yellowish to purple hues and to disfigure before shriveling up and dying; bud development is inhibited, the plants are stunted, and harvest is diminished. Growing tips could show signs of calcium deficiency if the humidity is maxed out. At 100 percent humidity, the stomata close, which stops the transpiration to protect the plant. The calcium that is transported by transpiration becomes immobile.

Treat deficiencies by dissolving one-half teaspoon of hydrated lime per gallon of water. Water the deficient plants with calcium-dosed water as long as the symptoms persist. Or use a complete hydroponic nutrient that contains adequate calcium. Keep the pH of the growing medium stable.

Progression of deficiency symptoms at a glance:

Slow growth and young leaves turn very dark green.

New growing shoots discolor.

New shoots contort, shrivel, and die.

Bud development slows dramatically.

Toxicity is difficult to see in the foliage. It caus es wilting. Toxic levels also exacerbate deficiencies of potassium, magnesium, manganese, and iron. The nutrients become unavailable, even though they are present. If excessive amounts of soluble calcium are applied early in life, it can also stunt the growth. If growing hydroponically, an excess of calcium will precipitate with sulfur in the solution, which causes the nutrient solution to suspend in the water and to aggregate into clumps causing the water to become cloudy (flocculate). Once the calcium and sulfur combine, they form a residue (gypsum Ca(SO0)-2(HjO) ) that settles to the bottom of the reservoir.

Sulfur (S) - immobile

Practical Information: Many fertilizers contain some form of sulfur, and for this reason, sulfur is seldom deficient. Growers avoid elemental (pure) sulfur in favor of sulfur compounds such as magnesium sulfate. The nutrients combined with sulfur mix better in water.

Technical Information: Sulfur is an essential building block of many hormones and vitamins, including vitamin Br Sulfur is also an indispensable element in many plant cells and seeds. The sulfate form of sulfur buffers the water pH. Virtually all ground, river, and lake water contains sulfate. Sulfate is involved in protein synthesis and is part of the amino acid, cystine, and thiamine, which are the building blocks of proteins. Sulfur is essential in the formation of oils and flavors, as well as for respiration and the synthesis and breakdown of fatty acids. Hydroponic fertilizers separate sulfur from calcium in an "A" container and a "B" container. If combined in a concentrated form, sulfur and calcium will form crude, insoluble gypsum (calcium sulfate) and settle as residue to the bottom of the tank.

Deficiency: Young leaves turn lime-green to yellowish. As shortage progresses, leaves yellow interveinally and lack succulence. Veins remain green, and leaf stems and petioles turn purple. Leaf tips can burn, darken, and hook downward. According to literature, youngest leaves should yellow first. But Mauk from Canna Coco in the Netherlands, who has conducted detailed scientific experiments with nutrients, says, "We have repeatedly noticed that the symptoms were

Early stage of S deficiency.

Progression of S

Progression of S

most obvious in the older leaves." Sulfur deficiency resembles a nitrogen deficiency. Acute sulfur deficiency causes elongated stems that become woody at the base.

Sulfur deficiency occurs indoors when the pH is too high or when there is excessive calcium present and available.

Progression of deficiency symptoms at a glance:

Similar to nitrogen deficiency: older leaves turn a pale green.

Leaf stems turn purple and more leaves turn pale green.

Entire leaves turn pale yellow.

Interveinal yellowing occurs.

Acute deficiency causes more and Later stage of S deficiency. more leaves to develop purple leaf stems and yellow leaves.

Treat deficiency by fertilizing with a hydroponic fertilizer that contains sulfur. Lower the pH to 5.5 to 6. Add inorganic sulfur to a fertilizer that contains magnesium sulfate (Epsom salts). Organic sources of sulfur include mushroom composts and most animal manures. Make sure to apply only well-rotted manures to avoid burning the roots.

Toxicity: An excess of sulfur in the soil causes no problems if the EC is relatively low. At a high EC, the plants tend to take up more available sulfur which blocks uptake of other nutrients. Excess sulfur symptoms include overall smaller plant development and uniformly smaller, dark-green foliage. Leaf tips and margins could discolor and burn when severe.

Treat toxicity by flushing the growing medium

of affected plants witli a very mild and complete fertilizer. Check the pH of the drainage solution. Correct the input pl-l to 6. Severe problems require more water to be flushed through the growing medium. Flush a minimum of three times the volume of water for the volume of the growing medium.


Micronutrients, also called trace elements or trace nutrients, are essential to chlorophyll formation and must be present in minute amounts. They function nainly as catalysts to the plant's process and utilization of other elements. For best results, and to ensure a complete range of trace elements is available, use fertilizers designed for hydroponics. High quality hydroponic fertilizers use food-grade ingredients that are completely soluble and leave no residues. If using an inexpensive fertilizer that does not list a specific analysis for each trace element on the label, it's a good idea to add soluble trace elements ir a chelated form. Chelated micronutrients are available in powdered and liquid form. Add and thoroughly mix micronutrients into the growing medium before planting. Micronutrients are often impregnated in commercial potting soils and soilless mixes. Check the ingredients on the bag to ensure that the trace elements were added to the mix. Trace elements are necessary in minute amounts but can easily reach toxic levels. Always follow the manufacturer's instructions to the letter when applying micronutrients, because they are easy to over apply. Zinc (Zn) - mobile


Zinc, iron, and manganese are the three most common micronutrients found deficient. Deficiencies of these three micronutrients plague many more grow rooms than I had imagined. Often deficiencies of all three occur concurrently, especially when the soil or water pH is above 6.5. Deficiencies are most common in arid climates-Spain, the Southwestern United States, Australia, etc.-with alkaline soil and water. All three have the same initial symptom of deficiency: interveinal chlorosis of young leaves. It is often difficult to distinguish which element-zinc, iron, or manganese-is deficient, and all three could be deficient. This is why treating the problem should include adding a chelated dose of all three nutrients.

A chelate (Creek for daw) is an organic molecule that forms a daw-like bond with free electrically charged metal particles. This property keeps metal ions such as zinc, iron, and manganese, etc., soluble in water, and the chelated metal's reactions with other materials is suppressed. Roots take in the chelated metals in a stable, soluble form that is used immediately.

Natural chelates such as humic acid and citric acid can be added to organic soil mixes. Roots and bacteria also exude natural chelates to promote the uptake of metallic elements. Man-made chelates are designed for use in different situations. DTPA is most effective in a pH below 6,5, EDDHA is effective up to a pH of 8, and EDTA chelate is slow to cause leaf burn.

Chelates decompose rapidly in low levels of ultraviolet (UV) light including light produced by HID bulbs and sunlight. Keep chelates out of the light to protect them from rapid decomposition.

Chelate - combining njtrients in an atomic ring that is easy for plants to absorb.

This information was condensed from Canna Products,

Practical Information: Zinc is the most common micronutrient found deficient in arid climates and alkaline soils.

Technical Information: Zinc works with manganese and magnesium to promote the same enzyme functions. Zinc cooperates with other elements to help form chlorophyll as well as prevent its demise. It is an essential catalyst for most plants' enzymes and auxins, and it is crucial for stem growth. Zinc plays a vital part in sugar and protein production. It is fairly common to find zinc-deficient cannabis. Deficiencies are most common in soils with a pH of 7 or more.

Deficiency: Zinc is the most common micronutrient found deficient. First, younger leaves exhibit interveinal chlorosis, and new leaves and growing tips develop small, thin blades that contort and wrinkle. The leaf tips, and later the margins, discolor and burn. Burned spots on the leaves could grow progressively larger. These symptoms are often confused with a lack of manganese or iron, but when zinc deficiency is severe, new leaf blades contort and dry out Flower buds also contort into odd shapes, turn crispy dry, and are often hard. A lack of zinc stunts all new growth including buds.

Progression of deficiency symptoms at a glance:

Interveinal chlorosis of young leaves.

New (eaves develop thin, wispy leaves. Leaf tips discolor, turn dark, and die back.

New growth contorts horizontally.

New bud and leaf growth stops.

Treat zinc-deficient plants by flushing the growing medium with a diluted mix of a complete fertilizer containing chelated trace elements, including zinc, iron, and manganese. Or add a quality-brand hydtoponic micronutrient mix containing chelated trace elements.

Toxicity: Zinc is extremely toxic in excess. Severely toxic plants die quickly. Excess zinc interferes with the iron's ability to function properly and causes an iron deficiency.

Manganese (Mn) - immobile

Practical Information: Manganese deficiency is relatively common indoors.

Technical Information: Manganese is engaged in the oxidation-reduction process associated with the photosynthetic electron transport. This element activates many enzymes and plays a fundamental part in the chloroplast membrane system. Manganese assists nitrogen utilization along with iron in chlorophyll production.

Deficiency: Young leaves show symptoms first. They become yellow between veins (interveinal chlorosis), and the veins remain green. Symptoms spread from younger to older leaves as the deficiency progresses. Necrotic (dead) spots develop on severely affected leaves which become pale and fall off; overall plant growth is stunted, and maturation may be prolonged. Severe deficiency looks like a severe lack of magnesium.

Treat deficiency: Lower the pH, leach the soil, and add a complete, chelated micronutrient formula.

Progression of deficiency symptoms at a glance:

Interveinal chlorosis of young leaves forms.

Interveinal chlorosis of progressively older leaves forms.

Dead spots develop on acutely affected leaves.

Toxicity: Young and newer growth develop chlorotic, dark orange to dark, rusty-brown mottling on the leaves. Tissue damage shows on young leaves before progressing to the older

Progression ofZn defaency.

Later stage ofZn dckicncy.

liarfy stage of Mn deficiency.

leaves. Growth is slower, and overall vigor is lost. Toxicity is compounded by low humidity. The additional transpiration causes more manganese to be drawn into the foliage. A low pH can cause toxic intake of manganese. An excess of manganese causes a deficiency of iron and zinc.

Progression of Mn deficiency.

Iron (Fe) - immobile

Practical Information: Iron is available in a soluble chelated form that is immediately available for absorption by the roots. Deficiency fljp J indoors is common in m .M m alkaline soils.

Technical Information: Iron is fundamental to the enzyme systems and to transport electrons during photosynthesis, respiration, and chlorophyll production. Iron permits plants to use the energy provided by sugar. A catalyst for chlorophyll production, iron is necessary for nitrate and sulfate reduction and assimilation. Iron colors the earth from brown to red, according to concentration. Plants have a difficult time absorbing iron. Acidic soils normally contain adequate iron for cannabis growth.

Deficiency: iron deficiencies are common when the pH is above 6.5 and uncommon when the pH is below 6.5. Symptoms may appear during rapid growth or stressful times and disappear by themselves. Young leaves are unable to draw immobile iron from older leaves, even though ¡1 is present in the soil. The first

Later stage of Mn Deficiency.

symptoms appear on the smaller leaves as veins remain green and areas between the veins turn yellow. Interveinal chlorosis starts at the opposite end of the leaf tip: the apex of the leaves attached by the petiole. Leaf edges can turn upward as the deficiency progresses. Leaves fall off in severe cases. Iron deficiency is sometimes traced to an excess of copper. See "Copper."

Progression of Fe deficiency.

Later stage of Fe deficiency.

Progression of deficiency symptoms at a glance:

Younger leaves and growing shoots turn pale green and progress to yellow between the veins starting at the petiole but the veins remain green.

More and more leaves turn yellow and develop interveinal chlorosis.

Larger leaves finally yellow and develop i interveinal chlorosis. Jm. ;

In acute cases, ^^ Jf leaves develop necrosis and drop.

Treat iron deficiencies by lowering the soil pH to 6.5 or less. Avoid fertilizers that contain excessive amounts of manganese, zinc, and copper, which inhibit iron uptake. High levels of phosphorus compete with the uptake of iron. Improve the drainage; excessively wet soil holds little oxygen to spur iron uptake. Damaged or rotten roots also lower iron uptake. Increase root-zone temperature. Apply chelated iron in liquid form to root zone. Chelates are decomposed by light and must be thoroughly mixed with the grow ing medium to be effective. Exposing the nutrient solution to light causes depleted iron. Sterilizing the nutrient solution with UV light causes iron to precipitate. Leaves should green up in four or five days. Complete, balanced, hydroponic nutrients contain iron, and deficiencies are seldom a problem. Organic sources of iron, as well as chelates, include cow, horse, and chicken manure. Use only well-rotted manures to avoid burning plants.

Toxicity: Excess of iron is rare. High levels of iron do not damage cannabis, but it can interfere with phosphorus uptake. An excess of iron causes the leaves to turn bronze accompanied by small, dark brown leaf spots. If iron chelate is over applied, it will kill the plant in a few days.

Treat excess iron by leaching plants heavily.

The following group of micronutrients is seldom found deficient. Avoid deficiencies by using a high-quality hydroponic fertilizer that contains chelated micronutrients.

Boron (B) - immobile

Practical Information: Usually causes no problems, but boron must be available during the entire life of a plant.

Technical Information: Boron deficiencies seldom occur indoors. Boron is still somewhat of a biochemical mystery. We know that boron helps with calcium uptake and numerous plant functions. Scientists have collected evidence to suggest boron helps with synthesis, a base for the formation of nucleic acid (RNA uracil) formation. Strong evidence also supports boron's role in cell division, differentiation, maturation, and respiration as well as a link to pollen germination.

Deficiency: Stem tip and root tip grow abnormally. Root tips often swell, discolor, and stop elongating. Growing shoots look burned and may be confused with a burn from being too close to the HID light, First leaves thicken and become brittle, top shoots contort and/or turn dark, which is later followed by progressively lower-growing shoots. When severe, growing tips die, and leaf margins discolor and die back in places. Necrotic spots develop between leaf veins. Root steles (insides) often become mushy-perfect hosts for rot and disease. Deficient leaves become thick, distorted, and wilted with chlorotic and necrotic spotting.

Treat boron-deficient plants with one teaspoon of boric acid per gallon of water. You can apply this solution as a soil drench to be taken up by the roots, or apply hydroponic micronutrients containing boron. Hydroponic gardeners should keep boron dosage below 20 parts per million (ppm), because boron quickly becomes toxic if it is concentrated in the solution.

Toxicity: Leaf tips yellow first, and as the toxic conditions progress, leaf margins become necrotic toward the center of the leaf. After the leaves yellow, they fall off. Avoid using excessive amounts of boric acid-based insecticides.

Chlorine (Chloride) (CI) - immobile

Practical Information: Chloride is found in many municipal water systems. Cannabis tolerates low levels of chlorine. It is usually not a component of fertilizers and is almost never deficient in gardens that grow cannabis.

Technical Information: Chlorine, in the form of chloride, is fundamental to photosynthesis and cell division in the roots and the foliage. It also increases osmotic pressure in the cells, which open and close the stomata to regulate moisture flow within the plant tissue.

Deficiency: It is uncommon to be deficient. Young leaves pale and wilt, and roots become stubby. As the deficiency progresses, leaves become chlorotic and develop a characteristic bronze color. The roots develop thick lips and become stunted. NOTE: Both severe deficiency and excess of chloride have the same symptoms: bronze-colored leaves.

Treat chlorine deficiencies by adding chlorinated water.

Toxicity: Young leaves develop burned leaf tips and margins. Very young seedlings and clones are the most susceptible to damage. Later, the symptoms progress throughout the plant Characteristic yellowish-bronze leaves are smaller and slower to develop.

Treat toxic signs of chlorine by letting heavily chlorinated water sit out overnight, stirring occasionally. Chlorine will volatize and disappear into the atmosphere. Use this water to mix the nutrient solution or to irrigate the garden.

Cobalt (Co) - immobile

Practical Information: This nutrient is seldom mentioned as necessary for plant growth, and most fertilizer labels do not include cobalt. Cobalt is virtually never deficient in indoor cannabis gardens.

Technical Information: Cobalt is necessary for countless beneficial bacteria to grow and flourish. It is also vital for nitrogen absorption. Scientific evidence suggests this element is linked to enzymes needed to form aromatic compounds.

Deficiency: When deficient, the problems with nitrogen availability occur.

Copper (Cu) - immobile

Practical Information: Copper is concentrated in the roots. It is also used as a fungicide.

Technical Information: Copper is a component of numerous enzymes and proteins. Necessary in minute amounts, copper helps with carbohydrate metabolism, nitrogen fixation, and the process of oxygen reduction. It also helps with the making of proteins and sugars.

Deficiency: Copper deficiencies are not rare. Young leaves and growing shoots wilt, leaf tips and margins develop necrosis and turn a dark, copper-gray. Occasionally, an entire copper-deficient plant wilts, drooping even when adequately watered. Growth is slow and the yield decreases. A small deficiency can cause new shoots to die back.

Treat copper deficiency by applying a copper-based fungicide such as copper sulfate. Do not apply if the temperature is above 75°F (24°C) to avoid burning the foliage. Apply a complete hydroponic nutrient that contains copper. Cannabis plants seldom develop a copper deficiency.

Toxicity: Copper, although essential, is extremely toxic to the plant even in minor excess. Toxic levels slow the overall plant growth. As the toxic level climbs, symptoms include interveinal iron chlorosis (deficiency) and stunted growth, Fewer branches grow, and the roots become dark, thick, and slow growing. Toxic conditions accelerate quickly in acidic soils. Hydroponic gardeners must carefully monitor their solution to avoid copper excess.

Treat toxicity: Flush the soil or the growing medium to help expel the excess copper. Do not use copper-based fungicides.

Molybdenum (Mb) - immobile

Practical Information: Molybdenum is seldom deficient.

Technical Information: Molybdenum is a part of two major enzyme systems that convert nitrate to ammonium. This essential element is used by cannabis in very small quantities. It is most active in roots and seeds.

Deficiency: This micronutrient is almost never found deficient in cannabis. Deficiency promotes nitrogen shortage. First, the older and middle-aged leaves yellow, and some develop interveinal chlorosis; then the leaves continue to yellow and develop cupped or rolled-up margins as the deficiency progresses. Acute symptoms cause the leaves to become severely twisted, die, and drop. Overall growth is stunted. Deficiencies are worst in acidic soils.

Toxicity: Excess is uncommon in marijuana gardens. An excess of molybdenum causes a deficiency of copper and iron,

Practical Information: Silicon is readily available in most soils, water, and as far as I know, it does not cause cannabis any complications due to deficiencies or excesses.

Technical Information: Silicon is absorbed by the plants as silicic acid. Silicon assists in keeping iron and manganese levels consistent. It is found mainly in the epidermal cell walls where it collects in the form of hydrated amorphous silica. It also accumulates in the walls of other cells. Adequate and soluble silicon guarantees stronger cell walls that resist pest attacks and increase heat and drought tolerance.

Deficiency: A lack of silicon has been proven to decrease yields of some fruits and cause new leaves to deform.

Excess: Never heard of a problem.

NOTE: Pests and diseases have a difficult time penetrating the plants that are sprayed with a silicon-based repellent/insecticide.

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Fertilizers show the N-P-K in big letters on the front of the package.

Enzymes require nickel to break clown and use the nitrogen from the urea. It is also essential to iron absorption. Seldom deficient and subtly mixed with other nutrient deficiencies, most commonly nitrogen.

This is one of the problem elements. A little bit will go a long way! Sodium is taken up by the roots very quickly and in small amounts (50 ppm). It can block enough other nutrients causing severe deficiencies to result. When mixed with chlorine, it turns into table salt, which is the worst possible salt to put on the plants. Be very careful to measure your input water to ensure that it contains less than 50 ppm sodium. The less sodium in the solution, the better.

The goal of fertilizing is to supply the plants with the proper amounts of nutrients for vigorous growth, without creating toxic conditions by overfertilizing. A 2-gallon (8 L) container full of rich, fertile potting soil will supply all the necessary nutrients for the first month of growth, but the development might be slow. After the roots have absorbed most of the available nutrients, more must be added to sustain vigorous growth. Unless fortified, soilless mixes require fertilization from the start. I like to start fertilizing fortified soilless mixes after the first week or two of growth. Most commercial soilless mixes are fortified with trace elements.

Marijuana's metabolism changes as it grows and so do its fertilizer needs. During germination and seedling growth, intake of phosphorus is high. The vegetative growth stage requires larger amounts of nitrogen for green-leaf growth, and phosphorus and potassium are also necessary in substantial levels. During this leafy and vegetative growth stage, use a general purpose or a grow fertilizer with high nitrogen content. In the flowering stage, nitrogen takes a backseat to potassium, phosphorus, and calcium intake. Using a super bloom fertilizer with less nitrogen and more potassium, phosphorus, and calcium promotes fat, heavy, dense buds. Cannabis needs some nitrogen during flowering, but very little. With no nitrogen, buds do not develop to their full potential.

Some water systems are abundant with fluoride. If concentrated, fluoride can become toxic. I have yet to see fluoride toxicity or deficiency cause problems in an indoor grow room.

Continue reading here: Fertilizers

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