Plants are bio-factories. In order for these factories to work/manufacture, they require raw materials such as: Light, Oxygen, Hydrogen (Water), Carbon Dioxide and Nutrients (both macro and micro).
Nitrogen, Phosphorus, Potassium often represented as N-P-K are three nutrients are absorbed in the largest quantities by plants and are known as Macro Nutrients. They serve absolutely vital roles in a plant’s development.
It is important for gardeners to be able to identify any nutritional disorders and how they can be rectified.
N – Nitrogen
Nitrogen is a unique element, as plants are able to take up nitrogen in the form of an anion (a negatively charged molecule) or a cation (a positively charged molecule). Plants are able to take nitrogen in as NO 3 or Nitrates and NH 4 Ammonium. Plants require or consume more nitrates than ammonia. A well balanced nutrient solution will have less than 10% of available nitrogen in the form of ammonia. Nitrogen has many functions in the plant; it is found in proteins, chlorophyll, protoplasm and plant hormones. Necessary for the formation of amino acids, co-enzymes, and chlorophyll.
Deficiency – Growth is slow, sparse and spindly the older leaves turn yellow and will eventually dry out and die. The complete leaf will turn yellow, with no green veins.
Toxicity – The plants will produce excess foliage that will be dark green. The plants will also be softer, disease and insect outbreaks will be severe (this will be due to a weaker softer plant). The root system will also be underdeveloped. High nitrogen levels can also retard flowering and fruiting, lower fruit quality and decrease yields as flowers don’t set. Nitrogen deficiency and toxicity is rare and will not be a problem if growers use premixed nutrients and follow the directions for these nutrients.
P – Phosphorus
Phosphorus is a very important nutrient for plants. It is required by seedlings, newly rooted clones and flowering and fruiting plants. Phosphorus is essential for the development of healthy roots, stimulation of flowering, ripening of fruits and seed production. Phosphorus is also required for the hydrolysis of starch to sugar and for the synthesis of starch to sugars (also known as energy transfer). Helps to produce flowers and fruits, as well as stimulates root growth.
Deficiency – Plants are stunted and the leaves turn dark green to purplish in color. This is due to a buildup of Anthocyanin pigments. These symptoms normally occur in the older leaves first. Plant maturity will also be delayed and yields will be low. Seed production is also severely affected.
Toxicity – Phosphorus toxicity is very difficult to diagnose. Excess phosphorus will cause deficiencies of calcium, iron, copper and zinc. This will cause confusing signals as other minerals may be showing signs of deficiencies even when adequate amounts of these minerals are present.
K – Potassium
Potassium is the catalyst in plants. It is important for the manufacture and transport of plant sugars/carbohydrates, increases the chlorophyll in leaves, regulates the opening and closing of the leaf stomata, disease resistance, water uptake and ripening process of fruits. Potassium is also found in the juice of fruits which contributes to an increase of fruit taste and fruit quality. High levels of this element are required for protein synthesis. Helps to manufacture sugars and starches, as well as contributes to root growth and plant hardiness.
Deficiency – Symptoms occur in older leaves first with yellow blotches and in severe cases dead spots will occur. Branches and stems will weaken and eventually becomes brittle. Flowering and fruiting is diminished and yields are low and poor in quality.
Toxicity – leaf margins may burn in sever cases, but often it will effect the uptake of magnesium and magnesium deficiencies will occur.
Plants need more than the three macro nutrients to thrive.
The following nine elements are known as Micro Nutrients, and are required in smaller quantities for a healthy plant.
Boron – Combined with Calcium, helps to form cell walls.
Calcium – Combined with Boron, helps to form cell walls.
Calcium is as important as N, P and K. Calcium is required in the roots, stems, leaves and fruits of plants. It is found in every cell wall and is required for the absorption of nitrogen.
Deficiency – Flower bud development is retarded, thus reducing yields, and fruit size is decreased. Roots die, leaving the plant open to root rot attack. Young leaves show symptoms before older leaves. The leaves can be deformed, and have yellow blotches which later turn into dead spots.
Toxicity – No visual symptoms; may cause magnesium deficiency.
Copper – Activates enzymes and is required for respiration and photosynthesis.
Iron – Used to form chlorophyll and in respiration of sugars for energy.
Magnesium – Catalyzes the growth process and makes oxygen during photosynthesis.
Magnesium is found in the chlorophyll molecule. If a deficiency of magnesium occurs then magnesium is transported from the lower leaves to the new leaves. Magnesium uptake is affected by the concentration of potassium. If high levels of potassium are applied then the amount of magnesium should increase e.g. at the second week of flowering when blooming enhancers are used then Cal-Mag Plus should be applied.
Deficiency – Older leaves (lower half of the plants’ leaves) show signs of yellowing. The yellowing occurs between the leaf veins which remains green.
Toxicity – There are no visual symptoms for magnesium toxicity.
Sulfur – Synthesizes protein, helps with fruiting, seeding and water uptake. Also acts as an organic fungicide.
Zinc – Helps to form chlorophyll, along with assisting respiration and nitrogen metabolism.
Silicon accumulates mostly in the epidermal cells of a plant. It is also found in other cell walls. Silicon helps creates hardier, stronger plants and also increases the dry matter content of crops. It has also been known to increase the plants resistance to fungal attacks and also increases the plant's tolerance drought or under watering.
Deficiency – Deficiencies of silicon have been known to reduce yields.
Toxicity – Not known.