Essential Plant Nutrients Obtained Through Air, Water, and Soil

Seventeen elements are considered essential nutrients for plant growth, fourteen of which come from the soil. A deficiency of any essential element will prevent plants from completing their vegetative or reproductive cycles. Some of these nutrients combine to form compounds that make up cells and enzymes. Other nutrients are necessary for certain chemical processes to occur.

Primary Nutrients Essential to Plant Health

The following primary nutrients are needed by the plant in large amounts:

Nitrogen (N)
Primary role in the plant:
Plant green up and growth, helps chlorophyll production, flowering, and fruit development

Summary:
Nitrogen is a building block of plant proteins. It’s an integral part of chlorophyll and is a component of amino acids, nucleic acids and coenzymes. Most nitrogen in the soil in tied up in organic matter. It is taken up by plants as nitrate (NO3-) and ammonium (NH4+) ions from inorganic nitrate and ammonium compounds. These compounds can enter the soil as a result of bacterial action (nitrogen fixation), application of inorganic nitrogen fertilizer, or conversion of organic matter into ammonium and nitrate compounds. Not all nitrates in the soil are taken up by plants. Nitrates can be leached beyond the root zone in sandy soils or converted to nitrogen gas in wet, flooded soils. Nitrogen fixation by soil microbes immobilizes nitrogen, making it available for later use by plants.

Deficiency symptoms:

• Slow growth and stunting
• Yellow-green color leaves
• “Firing” of tips and margins of leaves; yellowing begins with mature leaves

Phosphorus (P)
Primary role in the plant:
Used by all parts of the plant root for growth, flowering, and fruit

Summary:
Plants use phosphorus to form the nucleic acids DNA and RNA and to store and transfer energy. Phosphorus promotes early plant growth and root formation through its role in the division and organization of cells. Phosphorus is essential to flowering and fruiting and to the transfer of hereditary traits. Phosphorus is adsorbed by plants as H2PO4-, HPO4-2, or PO-3, depending upon soil pH. The mobility of phosphorus in soil is low, and deficiencies are common in cool, wet soils.

Deficiency symptoms:

• Slow growth and stunting
• Purplish coloration on foliage of some plants
• Dark green coloration with tips of leaves dying
• Delayed maturity
• Poor fruit or seed development

Potassium (K)
Primary role in the plant:
Important in water transfer, stress tolerance, flowering and fruit development, disease resistance

Summary:
Potassium is necessary to plants for translocation of sugars and for starch formation. It’s important for efficient use of water through its role in opening and closing small apertures (stomata) on the surface of leaves. Potassium increases plant resistance to diseases and assists in enzyme activation and photosynthesis. It also increases the size and quality of fruits and improves winter hardiness.

Plants take up potassium in the form of potassium ions (K+). It’s relatively immobile in soils but can leach in sandy soils.

Deficiency symptoms:

• Tip and marginal “burn” starting on mature leaves. Lower leaves turn yellow.
• Weak stalks and plants lodge easily.
• Small fruits or shriveled seeds.
• Slow growth.

Secondary Nutrients Essential to Plant Health

Secondary nutrients are nutrients needed by the plant in amounts smaller than that of primary nutrients. Regardless, the following secondary nutrients are just as essential to plant health as primary nutrients:

Calcium (Ca)
Primary role in the plant:
Part of every plant cell, Calcium is essential to cell division and contributes to cell wall strength, fruit development, and quality.

Summary:
Calcium provides a building block (calcium pectate) for cell walls and membranes and must be present for the formation of new cells. It is a constituent of important plant carbohydrates, such as starch and cellulose. Calcium promotes plant vigor and rigidity and is important to proper root and stem growth.

Plants absorb calcium in the form of the calcium ion (Ca+).

Deficiency symptoms:

• “Tip burn” of young leaves — ie. celery, lettuce, cabbage
• Growing point dieback- death of growing points or terminal buds (root tips are also affected)
• Stunted root growth
• Premature shedding of blossoms and buds
• Weakened stems
• Water-soaked, discolored areas on fruits — ie. blossom-end rot of tomatoes, peppers, and melons, bitter pit or cork spot of apples and pears

Magnesium (Mg)
Primary role in the plant:
Magnesium is an important part of every cell and an integral part of chlorophyll, which makes it essential for photosynthesis.

Summary:
Magnesium is a component of the chlorophyll molecule and is therefore essential to photosynthesis. Magnesium serves as an activator for many plant enzymes required for sugar metabolism and movement and for growth processes. Plants take up magnesium as the Mg+2 ion.

Deficiency symptoms:

• Interveinal chlorosis or the yellowing of older leaves
• Curling of leaves upward along margins
• Marginal yellowing with green “Christmas tree” area along midrib
• Occur on acid, sandy soils
• Can be induced by high K applications

Sulfur (S)
Primary role in the plant:
Sulfur works with N in synthesis of S-amino acids in the production of plant protein and fruit development.

Summary:
Sulfur is a constituent of three amino acids; cystine, methionine, and cysteine, that play an essential role in protein synthesis. Sulfur is present in oil compounds responsible for

characteristic odors of plants such as garlic and onion. It is also essential for nodule formation on legumes.

Plants take up sulfur in the form of sulfate (SO4-2) ions.

Deficiency symptoms:

• Young leaves are light green to yellowish in color. In some plants, older tissues are also affected.
• Small and spindly plants
• Reduced growth and maturity

Essential Micronutrients for Plant Health

The following are micronutrients, which are nutrients needed by the plant only in small amounts:

Zinc (Zn)
Primary role in the plant:
Needed for normal growth and reproduction, essential part of enzyme system related to plant growth

Summary:
Zinc is an essential component of several enzymes in plants. It controls the synthesis of indoleacetic acid, an important plant growth regulator, and it’s involved in the production of chlorophyll and protein. Zinc is taken up by plants as the zinc ion (Zn+2).

Deficiency symptoms:

• Decreasing in stem length and a rosetting of terminal leaves.
• Reduced fruit bud formation.
• Dieback of twigs after the first year.
• Mottled leaves and interveinal chlorosis.

Iron (Fe)
Primary role in the plant:
Enhances rich green color, chlorophyll synthesis, and photosynthesis

Summary:
Iron is taken up by plants as ferrous ion (Fe+2). Iron is required for the formation of chlorophyll in plant cells. It serves as an activator for biochemical processes such as respiration, photosynthesis, and symbiotic nitrogen fixation. Turf, ornamentals, and certain trees are especially susceptible to iron deficiency.

Deficiency symptoms:

• Interveinal chlorosis of young leaves — veins remain green except in severe cases
• Twig dieback
• In severe cases, death of limbs or plants

Manganese (Mn)
Primary role in the plant:
Important role in enzyme formation in plant cells and carbon dioxide assimilation

Summary:
Manganese serves as an activator for enzymes in plant growth processes, and it assists iron in chlorophyll formation. Plants obtain this nutrient from the soil in the form of manganous ion (Mn+2).

Deficiency symptoms:

• Interveinal chlorosis of young leaves
• Gradation of pale green color with darker color next to veins

Copper (Cu)
Primary role in the plant:
Essential role in chlorophyll production, promotes seed production and formation

Summary:
Copper is an activator of several enzymes in plants. It may play a role in production of vitamin A. Deficiency interferes with protein synthesis. Plants take up copper from the soil in the form of cuprous (Cu+) or cupric (Cu+2) ions.

Deficiency symptoms:

• Stunted growth
• Dieback of terminal shoots in trees
• Poor pigmentation
• Wilting and eventual death of leaf tips

Boron (B)
Primary role in the plant:
Essential for regulation of metabolism and cell division

Summary:
Boron regulates the metabolism of carbohydrates in plants. It is essential for the process by which meristem cells (cells that divide) differentiate to form specific tissues. Boron is taken up by plants as the borate ion (BO3-). Plants differ in their boron needs.

Deficiency symptoms:

• Death of terminal buds, causing lateral buds to develop and producing a “witches broom” effect
• Thickened, curled, wilted, and chlorotic leaves
• Soft or necrotic spots in fruit or tubers
• Reduced flowering or improper pollination

Molybdenum (Mo)
Primary role in the plant:
Essential for nitrogen utilization

Summary:
Molybdenum is taken up by plants as molybdate ions (MoO4-). Molybdenum is an essential micronutrient that enables plants to make use of nitrogen. Without molybdenum, plants cannot transform nitrate nitrogen to amino acids and legumes cannot fix atmospheric nitrogen.

Deficiency symptoms:

• Stunting and lack of vigor
• Marginal scorching and cupping or rolling of leaves

Chlorine (Cl)
Primary role in the plant:
Essential for photosynthesis

Summary:
Chlorine is required in photosynthetic reactions. Plants take up chlorine as chloride ion (Cl-).

Deficiency symptoms:

• Wilting followed by chlorosis (yellowing)
• Excessive branching of lateral roots
• Bronzing of leaves