Come individuare le carenze e gli eccessi dei principali elementi nutritivi e microelementi. -

Nutrient Deficiencies further details and indications

How to identify, with a simple glance, the deficiencies and excesses of the main nutritional elements that can be found in cannabis plants.

How to spot fertilizer deficiencies and excesses in cannabis cultivation.

Primary nutrients or Macroelements

Nitrogen (N) (mobile element):  

Nitrogen is a fundamental element for the growth of cannabis plants, playing a primary role in vegetative development (leaves and stems) , in the production of chlorophyll and in photosynthesis.

Nitrogen deficiency: the older leaves (those on the lower part) progressively yellow and a slowdown in the general development of the plant is observed. Being a mobile element, this is able to use any excess nitrogen located in the plant organism to compensate for the deficiencies of a specific area. In case of lack of nitrogen, to restore color and vigor to the plants, simply water with a nutrient solution rich in this element and having an adequate pH.

Excess nitrogen: the leaves acquire a shiny dark green hue which, starting from the edges, spreads throughout the entire leaf mass. The tips, however, fold downwards in the shape of an eagle's claw. To reverse the situation, you need to wash the substrate with plenty of water in a bathtub for about 15-20 minutes, let it dry well and prepare a solution of just water and enzymes to use in the next irrigation. You will see that the plants regain balance quickly.


Phosphorus (P) (mobile):  

like nitrogen, phosphorus is essential for plant growth, particularly regarding the production of new shoots and root development. This is why root stimulators are often rich in phosphorus. During flowering, however, the nutrient plays a central role in  production of flowers and terpenes , and is important for correct photosynthetic activity on a general level.


Phosphorus deficiency: the general development of the plant slows down and the new leaves, smaller in size than those observed in healthy specimens, wither quickly. The edges appear slightly folded upwards and develop an opaque bluish color, while the stems and petioles turn purple, sometimes developing brown spots next to the vein. To solve the problem, simply use a fertilizer rich in phosphorus and with an adequate pH. Finally, it is important to keep in mind that phosphorus deficiencies are often caused by too much zinc or iron.

Excess phosphorus: Excess phosphorus is difficult to detect because it often prevents the assimilation of other elements (potassium, calcium, magnesium, zinc, copper and iron). The solution passes through a thorough washing of the substrate, to be strengthened with three consecutive irrigations with only water and an adequate pH, after which you can gradually reintroduce normal fertilization schemes.


Potassium (K) (mobile):  

together with phosphorus, potassium contributes to the correct development of roots , while in collaboration with nitrogen, it takes care of the production of chlorophyll and the development of flowers . Furthermore, it significantly improves the resistance of plants to cryptogamic diseases and other types of stress.

Potassium deficiency: the general development of the plant is altered and the edges of the leaves become curved and dry until they become brown. The rest of the leaf surface progressively yellows and develops brown spots. To solve the problem, simply apply a fertilizer rich in potassium after adjusting the pH.

Excess potassium: as in the case of phosphorus, an excess of potassium can block the assimilation of other elements such as magnesium, manganese, zinc and iron. The solution is the same as for excess phosphorus.


Secondary nutrients

Sulfur (S) (non-mobile element):  

sulfur participates directly in the growth of the various organs of the plant structure , also intervening in the production and regulation of hormones and vitamins . In addition to being crucial during growth, it also plays a fundamental role in the production of chlorophyll, as well as in the aroma and flavor of flowers .

Sulfur deficiency: plant growth slows and leaves develop chlorosis. The petioles acquire a purple hue and the stems become woody and break easily. Sometimes, the smaller leaves develop mutations and curl upwards slightly before wilting and falling off. During flowering, some inflorescences show the presence of necrosis. This type of deficiency is easily resolved by using epsom salt or a high-sulfur fertilizer.

Excess sulphur: the general development of the plant slows down considerably, the green color evolves towards a darker shade and the tips of the leaves wither and dry. Problems with excess sulfur are uncommon as it is an element that, in most cases, the plant manages well without external interventions.

Calcium (Ca) (non-mobile):  

an indispensable secondary element for the formation and strengthening of cell walls and all plant tissues . It participates in the development of the roots and exerts a buffering effect, as it has the ability to regulate, within certain limits, the excess of other nutrients, guaranteeing a certain nutritional balance.

Calcium deficiency: the general development of the plant slows down, particularly at the root level, and a clear loss of vegetative vigor is observed. The leaves develop obvious deformations, with irregular edges and tips that curl. This deformation is also observed on the youngest leaves, which discolor and wilt quickly. If the plant is flowering, the production of flowers gradually decreases until it stops completely. To solve this type of deficiency, just use a fertilizer rich in calcium.

Excess calcium: Excess calcium can hinder the absorption of other nutrients such as potassium, magnesium, manganese and iron. In the presence of this type of deficiency, it is recommended to wash the roots thoroughly and apply a fertilizer containing all the necessary macro and micronutrients but in limited and balanced quantities.

Magnesium (Mg) (mobile):  

participates in the production of chlorophyll and photosynthesis, intervenes in the activation of various enzymatic mechanisms and promotes the absorption of other nutrients .

Magnesium deficiency: magnesium deficiency manifests itself through symptoms very similar to those of nitrogen deficiency. As in the case already described, the older leaves, located in the lower part of the plant, begin to yellow (chlorosis), a phenomenon which then spreads to the rest of the plant. The leaves thus continue to discolour, deforming up to the tips. Again, the solution is simple: just apply a single-element magnesium-based fertilizer and adjust the pH correctly.

Excess magnesium: Although not very common, excess magnesium can hinder the absorption of calcium. As in the previous cases, it is advisable to wash the substrate thoroughly and use a balanced fertilizer containing all the nutrients necessary for the development of the plant, to be applied in moderate doses in the next irrigation (after having adjusted the pH).


Iron (Fe) (non-mobile) :

iron is fundamental for photosynthesis, for the production of chlorophyll and also at a respiratory level (good functioning of the enzymatic systems). The element also contributes to the correct assimilation of nitrates and sulfates .


Iron deficiency: the leaves and young shoots progressively yellow starting from the petiole, while the veins remain green. As the deficiency progresses, intervenous chlorosis also manifests itself on the remaining leaves until it covers the entire leaf mass. If the symptoms are not treated in time, the leaves become necrotic and end up falling. The solution goes through a thorough washing of the roots using a diluted nutrient solution containing iron, zinc and manganese. Differentiating between the deficiencies of these three elements, which often occur simultaneously, is somewhat complicated, which is why we recommend the joint application of the three nutrients.

Excess iron: the leaves acquire a bronzed color accompanied by the appearance of very dark brown spots. To solve the problem, simply wash the substrate with a very diluted nutrient solution (equal to three times the capacity of the pot).

Zinc (Zn) (mobile):

actively participates in the production of chlorophyll and the preservation of plant tissues.

Zinc deficiency: Young leaves develop chlorosis between the veins and new leaves, which do not fully grow or form, become twisted. The tips gradually discolor and burn. From a more global point of view, a slowdown in the general development of the plant is observed. If the deficiency occurs during flowering, the flowers become deformed, dry and become brittle. The solution is the same as for iron deficiency.

Excess zinc: this is unfortunately a fairly difficult problem to treat. In most cases, the plant dies before action can be taken following an iron deficiency caused by excess zinc.

Manganese (Mn) (non-mobile):  

plays an important role in photosynthesis and the development of chloroplast membranes (plant cell development).

Manganese deficiency: Young leaves show interveinal chlorosis followed by necrotic spots, which gradually spread to older leaves. The general development of the plant slows down or even stops. The solution is the same as for the lack of iron and zinc.

Excess manganese: the younger leaves develop a particular type of chlorosis characterized by a spotty color ranging from dark orange to rusty brown, and which then spreads to the older leaves, with a significant loss of vigor. This phenomenon causes the plant to transpire, which ends up developing an iron and zinc deficiency.

Boron (B) (non-mobile):

Boron still constitutes a sort of biochemical mystery. The only certainty is that it intervenes in cell division and differentiation, in the production of pollen and in the maturation and respiration of the plant .

Boron deficiency: The roots stop developing and the tips swell and become discolored. Growing shoots appear burnt, as if they were too close to a sodium lamp (HPS). The first to deform or regress are those located in the upper part of the plant, but as the deficiency progresses, the symptoms also appear in the lower part. In severe cases, both the growing shoots and the leaves, which become bulkier and develop necrotic spots and discolored edges that end up covering the entire leaf surface, wither and die. Often, the internal part of the roots becomes spongy, constituting an ideal environment for the appearance of diseases and fungi. To restore the normal development of the plant, just water with a solution containing four liters of water and 0.05 grams of boric acid.

Excess boron: the ends of the leaves turn yellow and the edges become necrotic starting from the center. Subsequently, they discolor and fall off. Unfortunately, there is no defined method to combat this phenomenon. In any case, you can try washing the substrate and applying a complete fertilizer in moderate doses.

Molybdenum (Mo) (non-mobile):  

It constitutes an integral part of two fundamental enzymatic systems that transform nitrates into ammonium . It is an essential trace element that plants use in very small quantities.

Molybdenum Deficiency: Molybdenum deficiency is not very common in indoor cultivation. In any case, when it occurs, the general development of the plant slows down and the older leaves turn yellow (some even show intervenal chlorosis). As the deficiency progresses, the yellowing becomes more evident and the edges of the leaves curl up. In severe cases, young leaves become narrower, curl severely and eventually die. Often, molybdenum deficiencies lead to sulfur deficiencies. To treat the problem, simply apply a solution formulated with four liters of water and 0.01 grams of molybdic acid or ammonium molybdate.

Excess molybdenum: excess molybdenum is more frequent than deficiency, and can in turn cause iron and copper deficiency (starting from 0.2 ppm).