stem growth, as well as overall size and vigor. Nitrogen is most active in young buds, shoots, and leaves. Ammonium (NH,r) is the most readily available form of nitrogen. Be careful when using too much of this form; it can burn the plants. Nitrate (NO,-)-the nitrate form of nitrogen-is much slower to assimilate than ammonium. Hydroponic fertilizers use this slower-acting nitrogen compound and mix it with ammonium.

Deficiency: Nitrogen is the most common nutrient deficiency. The symptoms include slow growth. Lower leaves cannot produce chlorophyll and become yellow between the veins while the veins remain green. Yellowing progresses through the entire leaf, eventually causing it to die and drop off. Stems and the leaves' undersides may turn reddish-purple, but this can also be a sign of a phosphorus deficiency. Nitrogen is very mobile, and it dissipates into the environment quickly. It must be added regularly to sustain fast-growing gardens.

Progression of deficiency symptoms at a glance:

Older leaves yellow between the veins (inter-veinal chlorosis).

Older bottom leaves turn entirely yellow.

More and more leaves yellow. Severely affected leaves drop.

Leaves might develop reddish-purple stems and veins on leaf undersides.

Progressively younger leaves develop inter-velnal chlorosis.

All foliage yellows and the leaf drop is severe.

Treat deficiency by fertilizing with N or a complete N-P-K fertilizer. You should see results in four to five days. Fast-acting organic sources of nitrogen include seabird guano, fish emulsion, and blood meal. Growers also report excellent results by adding bio-fertilizers (see Additives below) to stimulate the uptake of nitrogen.

Toxicity: An overdose of nitrogen will cause excessively lush foliage that is soft and susceptible to stress, including insect and fungal attacks. The stems become weak and they may fold over easily. The vascular transport tissue breaks down, and water uptake is restricted. In severe cases, leaves turn a brownish-copper color, dry.

Early stage oi N overdose. Later stage of N overdose.
Cannabis Sparse

Beginning of N deficiency and fall off. Roots develop slowly, and they tend to darken and rot. Flowers are smaller and sparse. Ammonium toxicity is most common in acidic soils, while nitrate toxicity is more prevalent in alkaline soil.

Progression of toxicity symptoms at a j

Excessively lush, ^ A

green foliage. \tK $

Weak stems that wjr fold over. "^/r y

Fliiwers become wispy.

Leaves brown, dry, and fall off.

Treat toxicity by flushing the growing medium of the affected plants with a very mild, complete fertiliser, Severe problems require that more water be flushed through the growing medium to carry away the toxic elements. Flush a minimum of three times the volume of water for the \ / volume of the grow- \ / ing medium. Do not \ '¡U / add more fertilizer \f that contains nitrogen —~^ for one week so the excess nitrogen in Laef stage of N deficiency.

Progression of N deficiency.

foliage can be used. If the plants remain excessively green, cut back on the nitrogen dose.

Phosphorus (P) - mobile

Practical Information: Cannabis uses the highest levels of phosphorus during germination, seedling, cloning, and flowering. Super Bloom fertilizers, designed for flowering, have high levels of phosphorus.

Technical Information: Phosphorus is necessary for photosynthesis and provides a mechanism for the energy to transfer within the plant. Phosphorus-one of the components of DNA, many being enzymes and proteins-is associated with overall vigor, resin, and seed production. The highest concentrations of phosphorus are found in root-growing tips, growing shoots, and vascular tissue.

Deficiency A lack of phosphorous causes stunted growth and smaller leaves; leaves turn bluish-green and blotches often appear. Stems, leaf stems (petioles), and main veins turn reddish-purple starting on the leaf's underside. NOTE: The reddening of the stems and the veins is not always well pronounced. The leaf tips of older leaves turn dark and curl downward. Severely affected leaves develop large purplish-black necrotic (dead) blotches. These leaves later become bronzish-purple, dry, shrivel up, contort, and drop off. Flowering is often delayed, buds are uniformly smaller,

Early stage of P deficiency.
Progression of P deficiency.

Later stage of P deficiency.

Later stage of P deficiency.

seed yield is poor, and plants become very vulnerable to fungal and insect attack. Phosphorus deficiencies are aggravated by clay, acidic, and soggy soils. Zinc is also necessary for proper utilization of phosphorus.

Deficiencies are somewhat common and are often misdiagnosed. Deficiencies are most common when the growing-medium pH is above 7 and phosphorus is unable to be absorbed property; the soil is acidic (below 5.8) and/or there is an excess of iron and zinc; the soil has become fixated (chemically bound) with phosphates.

Progression of deficiency symptoms at a glance:

Stunted and very slow-growth plants.

Dark bluish-green leaves, often with dark blotches.

Plants are smaller overall,

When blotches overcome the leaf stem, the leaf turns bronzish-purple, contorts, and drops.

Treat deficiency by lowering the pH to 5.5-6,2 in hydroponic units; 6 to 7 for clay soils; and 5.5-6,5 for potting soils so phosphorus will become available. If the soil is too acidic, and an excess of iron and zinc exists, phosphorous becomes unavailable. If you are growing in soil, mix a complete fertilizer that contains phosphorus into the growing medium before planting. Fertigate with an inorganic, complete hydroponic fertilizer that contains phosphorus. Mix in the organic nutrients-bat guano, steamed bone meal, natural phosphates, or barnyard manure-to add phosphorus to soil. Always use finely ground organic components that are readily available to the plants.

Toxic signs of phosphorus may lake several weeks to surface, especially if excesses are buffered by a stable pH. Marijuana uses a lot of phosphorus throughout its life cycle, and many varieties tolerate high levels. Excessive phosphorus interferes with calcium, copper, iron, magnesium, and zinc stability and uptake. Toxic symptoms of phosphorus manifest as a deficiency of zinc, iron, magnesium, calcium and copper; zinc is ihe most common.

Treat toxicity by flushing the growing medium of affected plants with a very mild and complete fertilizer. 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.

Potassium (K) - mobile

Practical Information: Potassium is used at all stages of growth. Soils with a high level of potassium increase a plant's resistance to bacteria and mold.

Technical information: Potassium helps combine sugars, starches, and carbohydrates, which is essential to their production and movement. It also is essential to growth by cell division. It increases the chlorophyll in the foliage and helps to regulate the stomata openings so plants make better use of the light and air. Potassium is essential in the accumulation and translocation of carbohydrates. It is necessary to make the proteins that augment the oil content and improve the flavor in cannabis plants. It also encourages strong root growth and is associated with disease resistance and water intake. The potash form of potassium oxide is (K,0).

Deficiency Potassium-starved plants initially appear healthy. Deficient plants are susceptible to disease. Symptoms include the following: older leaves (first tips and margins, followed by whole leaves) develop spots, turn dark yellow, and die. Stems often become weak and sometimes brittle. Potassium is usually present in the soil, but it is locked in by high salinity. First, leach the toxic salt out of the soil and then apply a complete N-P-K fertilizer. Potassium deficiency causes the internal temperature of the foliage to climb and the protein cells to burn or degrade. Evaporation is normally highest on leaf edges, and that's where the burning takes place.

The progression of the deficiency symptoms at a glance:

Plants appear healthy with dark green foliage.

The leaves lose their luster.

Branching may increase, but the branches are weak and scrawny.

Leaf margins turn grey and progress to a rusty-brown color, and then curl up and dry.

Yellowing of the older leaves is accompanied by rust-colored blotches.

Early stage of K deficiency.
Progression of K deficiency.

The leaves curl up, rot sels in, and the older leaves drop.

The flowering is retarded and greatly diminished.

Treat deficiency of potassium by fertilizing with a complete N-P-K fertilizer. Occasionally, a grower will add potassium directly to the nutrient solution. Organic growers add potassium in the form of soluble potash (wood ashes) mixed with water. Be careful when using wood ash, the pH is normally above 10. Use a pH-lowering mix to bring the pH to around 6.5 before application. Foliar feeding to cure a potassium deficiency is not recommended.

Toxicity occurs occasionally and is difficult to diagnose because it is mixed with the deficiency symptoms of other nutrients. Too much potassium impairs and slows tiie absorption of magnesium, manganese, and sometimes zinc and iron. Look for signs of toxic-potassium buildup when symptoms of magnesium, manganese, zinc, and iron deficiencies appear.

Treat toxicity by flushing the growing medium of affected plants with a very mild and complete fertilizer. Severe problems require that more water be flushed through the growing medium. Flush with a minimum of three times the volume of water for the volume of the growing medium.

Later stage of K deficiency.
Growing Soilless

Growing Soilless

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