What is fertilizer NPK?

Macronutrients, Excerpted from Chapter Four, Indoor Marijuana Horticulture, The Indoor Bible

Macronutrients

Macronutrients are the elements plants use the most. Fertilizers show the 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 growth.

Nitrogen (N) – mobile

Practical Stuff: Marijuana loves nitrogen and requires high levels during vegetative growth and lower levels during the balance of life. Nitrogen is easily washed away and must be replaced regularly, especially during vegetative growth. Excess levels of nitrogen in harvested plants cause dried marijuana to burn poorly.

Technical Stuff: Nitrogen regulates cannabis’s ability to make proteins essential for new protoplasm in the cells. It is essential for the production of amino acids, enzymes, nucleic acids, and chlorophyll and alkaloids. This important nutrient is mainly responsible for leaf and stem growth as well as overall size and vigor. Nitrogen is most active in young buds, shoots and leaves. Ammonium (NH4+) – This form of nitrogen is the most readily available. Be careful when using too much of this form, it can burn plants. Nitrate (NO3-) – The nitrate form of nitrogen is much slower to assimilate than ammonium. Hydroponic fertilizers use this nitrogen compound as slower acting and mix it with ammonium.

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

Progression of deficiency symptoms at a glance:

• Older leaves yellow between veins (interveinal 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 interveinal chlorosis
• All foliage yellows and leaf drop is severe

Treat deficiency by fertilizing with . . . See Indoor Marijuana Horticulture, the Indoor Bible

Toxicity: An overdose of nitrogen will cause excessively lush foliage that is soft and susceptible to stress including insect and fungal attacks. . . . See Indoor Marijuana Horticulture, the Indoor Bible

Treat toxicity by . . . See Indoor Marijuana Horticulture, the Indoor Bible

Phosphorus (P) – mobile

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

Technical Stuff: Phosphorus is necessary for photosynthesis and provides a mechanism for energy transfer within the plant. Phosphorus, a component of DNA, many enzymes and proteins, is associated with overall vigor as well as resin and seed production. Highest concentrations of phosphorus are found in root growing tips, growing shoots and vascular tissue.

Deficiency: A lack of phosphorous causes stunted growth. Leaves are smaller, bluish-green and often with blotches. . . . See Indoor Marijuana Horticulture, the Indoor Bible

Progression of deficiency symptoms at a glance:

• Stunted and very slow growth
• Dark bluish-green leaves often with dark blotches
• Plants are smaller overall
• When blotches overcome leaf stem, leaf turns bronzish-purple, contorts and drops.

Treat phosphorous deficiency by . . . See Indoor Marijuana Horticulture, the Indoor Bible

Toxic signs of phosphorus may take several weeks . . . See Indoor Marijuana Horticulture, the Indoor Bible.

Treat toxicity by . . . See Indoor Marijuana Horticulture, the Indoor Bible

Potassium (K) – mobile

Practical Stuff: Potassium is used at all stages of growth. Soils with a high level of potassium increase a plants resistance to bacteria and mold.

Technical Stuff: Potassium is essential to the manufacture and movement of sugars and starches, as well as growth by cell division. It increases chlorophyll in foliage and helps regulate stomata openings so plants make better use of light and air. Potassium is essential in the accumulation and translocation of carbohydrates. It also encourages strong root growth and is associated with disease resistance and water intake. The potash form of potassium oxide is (K2O).

Deficiency – Potassium-starved plants initially appear healthy. . . . See Indoor Marijuana Horticulture, the Indoor Bible.

Progression of deficiency symptoms at a glance:

• Plant appear healthy with dark green foliage
• Leaves loose luster
• Branching may increase but branches are weak and scrawny
• Leaf margins turn gray and progress to a rusty brown, curl up and dry
• Yellowing of older leaves accompanied by rust-colored blotches
• Leaves curl up, rot sets in and older leaves drop.
• Flowering retarded and diminished greatly.

Treat deficiency of potassium by . . . See Indoor Marijuana Horticulture, the Indoor Bible

Toxicity: Occurs . . . See Indoor Marijuana Horticulture, the Indoor Bible

Treat toxicity by . . . See Indoor Marijuana Horticulture, the Indoor Bible