Agri-Knowledge Hub

The 17 Essential Elements

Carbon (C)

Key Component : The backbone of all organic molecules, including sugars, starches, and cellulose (plant structure).

Deficiency : Stunted growth and poor structural development

(rare in nature as CO2 is abundant).

Source : Carbon dioxide (CO2) from the atmosphere.

Excess : Generally not toxic to plants directly, though high atmospheric levels affect global climates.

Hydrogen (H)

Key Component : Essential for pH balance, energy transfer, and

a major part of water and organic compounds.

Deficiency : Plants wilt, cells lose turgidity, and metabolic processes stop (caused by drought).

Source : Water (H2O).

Excess : Overwatering leads to oxygen deprivation in roots 
(root rot).

Oxygen (O)

Key Component : Vital for cellular respiration to produce energy from stored food.

Deficiency : Root suffocation and death, often occurring in compacted or waterlogged soil.

Source : Air and water.

Excess : High concentrations in the root zone are generally not harmful.

Nitrogen (N)

Key Component : A major part of chlorophyll, proteins, and amino acids. It drives vegetative growth.

Deficiency : Leaves turn pale yellow (chlorosis), starting from the bottom (older leaves) upwards. Stunted growth.

Source : Fertilizers (Urea), organic matter, and legumes.

Excess : Dark green, lush foliage but weak stems. The plant becomes susceptible to pests and diseases, and fruit/flower production is delayed.

Phosphorus (P)

Key Component : Essential for DNA, root development, flowering, and energy transfer (ATP).

Deficiency : Dark green leaves that may turn purple or reddish. Poor root systems and lack of flowers.

Source : Phosphate fertilizers, bone meal, and soil minerals.

Excess : Interferes with the uptake of micronutrients like Iron (Fe) and Zinc (Zn).

Potassium (K)

Key Component : Controls the opening and closing of stomata (breathing pores), water regulation, and enzyme activation.

Deficiency : "Burning" or browning of leaf edges (scorching).

Weak stems and poor-tasting fruit.

Source : Potash, compost, and mineral deposits.

Excess : Blocks the absorption of Magnesium (Mg)

and Calcium (Ca).

Calcium (Ca)

Key Component : Strengthens cell walls (the "skeleton" of the plant) and aids in cell signaling.

Deficiency : New leaves are distorted or hooked. Causes

"Blossom End Rot" in tomatoes and fruit cracking.

Source : Lime, gypsum, and crushed eggshells.

Excess : High levels can cause a deficiency in Potassium and Magnesium.

Magnesium (Mg)

Key Component : The central atom of the chlorophyll molecule. Without it, plants cannot photosynthesize.

Deficiency : Yellowing between leaf veins (interveinal chlorosis) on older leaves—veins stay green while the rest turns yellow.

Source : Dolomitic lime and Epsom salts.

Excess : Imbalances with Calcium uptake.

Sulfur (S)

Key Component : Essential for amino acids, proteins, and aromatic oils (gives onions and garlic their smell).

Deficiency : Entire plant turns pale yellow, similar to nitrogen deficiency, but starts on the younger leaves first.

Source : Organic matter, gypsum, and sulfate fertilizers.

Excess : Can lower soil pH significantly, making the soil too acidic

for some plants.

Iron (Fe)

Key Component : Essential for chlorophyll synthesis, energy transfer, and nitrogen fixation. It acts as an oxygen carrier.

Deficiency : Interveinal Chlorosis on young leaves. The leaf turns pale yellow or white, while the veins remain distinctly green.

Source : Iron chelates, ferrous sulfate, and natural soil minerals (though often "locked" in high pH soil).

Excess : Rare, but can cause brown spots on leaves and interfere with Phosphorus uptake.

Manganese (Mn)

Key Component : Vital for photosynthesis (splitting water molecules), respiration, and nitrogen assimilation.

Deficiency : Similar to iron deficiency but with a "checkered" or "net-like" pattern of yellowing on young leaves. Growth is often stunted.

Source : Manganese sulfate and organic matter.

Excess : Common in acidic soils; causes dark brown spots on older leaves and "crinkle leaf" (distorted leaf edges).

Boron (B)

Key Component : Critical for cell wall formation, reproductive health (pollen tube growth), and transporting sugars.

Deficiency : Death of growing points (buds). Stems become brittle, and fruits may have "hollow hearts" or internal corking (common in apples and root crops).

Source : Borax and Solubor.

Excess : Highly toxic in small increments. Leaf tips turn yellow, then brown (necrosis), and fall off prematurely.

Zinc (Zn)

Key Component : Helps produce Auxins (growth hormones) and is necessary for enzyme systems and protein synthesis.

Deficiency : "Little Leaf" or "Rosetting" (shortened internodes).

Leaves appear small, narrow, and clustered together.

Source : Zinc sulfate and zinc chelates.

Excess : Extremely toxic; plants will show symptoms of iron deficiency and roots may turn black and die.

Copper (Cu)

Key Component : Involved in photosynthesis, cell wall strength (lignin), and the plant’s immune system against diseases.

Deficiency : Young leaves become limp, wilted, and twisted. Often results in "dieback" of terminal buds and tips of branches.

Source : Copper sulfate and copper chelates.

Excess : Stunts root growth and causes iron-deficiency symptoms (yellowing) due to competition for absorption.

Molybdenum (Mo)

Key Component : The only micronutrient needed for converting Nitrates into Amino Acids. It is also essential for nitrogen-fixing bacteria in legumes.

Deficiency : Leaves turn yellow and pale. In some plants

(like cauliflower), it causes "Whiptail" where the leaf blade fails to develop, leaving only the midrib.

Source : Sodium molybdate and ammonium molybdate.

Excess : Plants are quite tolerant, but high levels in forage can be toxic to livestock (causing "Molybdenosis").

Chlorine (Cl)

Key Component : Regulates osmosis (water movement), gas exchange in stomata, and helps in the splitting of water during photosynthesis.

Deficiency : Leaves wilt at the margins and turn bronze or

blue-green. Roots may become highly branched but short.

Source : Rainwater, irrigation water, and potassium chloride (MOP).

Excess : Salt toxicity. Leaf margins burn (turn brown), and leaves drop. Very common in coastal areas or over-fertilized pots.

Nickel (Ni)

Key Component : Essential for the Urease enzyme, which breaks down urea into usable nitrogen. Important for seed germination.

Deficiency : Urea accumulates to toxic levels in the leaf, causing Necrosis (death) of the leaf tips. Seeds may fail to germinate or

be non-viable.

Source : Naturally occurring in most soils and organic composts.

Excess : Highly toxic; inhibits root development and causes chlorosis that mimics iron or zinc deficiency.