Nutrient Science

How cannabis plants take up, use and lose nutrients — from nitrogen form to flushing, from deficiency signs to toxicity thresholds.

  • Cannabis Nutrients

    Higher plants need fourteen nutrients, each with its own job, and their mobility decides where a deficiency first appears in cannabis.

  • Calculating a Nutrient Solution

    The nutrient calculator shows the nitrogen, phosphorus and potassium a mix delivers per litre beside results from cannabis trials.

  • Individual Nutrients

  • Macronutrients

  • Nitrogen (N)

    Nitrogen deficiency yellows the lower leaves first, and high nitrogen lowered the potency of the buds in trials.

  • Feeding and Flowering Onset

    In field hemp, scarce nitrogen delayed full flowering, and a delay from too much nitrogen has not been measured in cannabis.

  • Phosphorus (P)

    Phosphorus deficiency starts on the lower leaves, and in peat phosphorus above 25 mg/L brought no extra yield in trials.

  • Potassium (K)

    Potassium deficiency starts at the margins of the lower leaves, and above 175 mg/L potassium brought no extra yield in trials.

  • NPK Ratio

    Cannabis trials in perlite give a calculated 5:1:2 to 5:1:6 in veg and 5:1:2 in flower, but the amount matters more than the ratio.

  • Calcium (Ca)

    In vegetative growth calcium deficiency shows first on new growth, and it can appear in humid, still air even when enough is fed.

  • Magnesium (Mg)

    Magnesium deficiency turns the lower leaves yellow between green veins, and in perlite old leaves showed dead spots from 70 mg/L.

  • Sulphur (S)

    In vegetative growth sulphur deficiency first yellows the middle leaves, and without sulphur one cultivar lost 34 % of its bud yield.

  • Micronutrients and Beneficial Elements

  • Iron (Fe)

    Iron deficiency lightens the youngest leaves between green veins, and pH and root zone are checked before any iron is added.

  • Boron (B)

    Boron deficiency deforms the shoot tip of cannabis first, and with boron only a narrow range separates deficiency from toxicity.

  • Silicic Acid

    How cannabis takes up silicon, in which tissues it is deposited, and why with silicic acid products the solubility of the source matters more than its silicon content.

  • Nutrient Supply Disorders

  • Identifying Deficiencies

    Leaf pattern, progression and roots show whether cannabis suffers from a deficiency, an excess or something else entirely.

  • Diagnosis by Growing Medium

    Measuring pH and EC in the runoff, the slab drain or the tank shows whether a leaf problem comes from the root zone.

  • Nutrient Lockout

    With nutrient lockout the plant lacks a nutrient despite feeding, and the fix depends on the cause in the root zone or in the tank.

  • Leaf Senescence

    Leaf senescence yellows the oldest fan leaves in late flower even with full supply and is not a nutrient deficiency.

  • Cannabis Flushing

    Rinsing with plain water before harvest removed no nutrients from the flower in trials, left taste and ash unchanged and often cost yield.