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Competency Area 1: Basic Concepts of Plant Nutrition

PO 1 and PO 2. List the 18 elements essential for plant nutrition, and classify the essential elements as macronutrients or micronutrients.

  1. Macronutrients: used in large quantities by the plant
    1. Structural nutrients: C, H, O
    2. Primary nutrients: N, P, K
    3. Secondary nutrients: Ca, Mg, S
  2. Micronutrients: used in small quantities by the plant
    1. Fe, B, Cu, Cl, Mn, Mo, Zn, Co, Ni

Plants require eighteen elements found in nature to properly grow and develop. Some of these elements are utilized within the physical plant structure, namely carbon (C), hydrogen (H), and oxygen (O). These elements, obtained from the air (CO2) and water (H2O), are the basis for carbohydrates such as sugars and starch, which provide the strength of cell walls, stems, and leaves, and are also sources of energy for the plant and organisms that consume the plant.

Elements used in large quantities by the plant are termed macronutrients, which can be further defined as primary or secondary. The primary nutrients include nitrogen (N), phosphorus (P), and potassium (K). These elements contribute to plant nutrient content, function of plant enzymes and biochemical processes, and integrity of plant cells. Deficiency of these nutrients contributes to reduced plant growth, health, and yield; thus they are the three most important nutrients supplied by fertilizers. The secondary nutrients include calcium (Ca), magnesium (Mg), and sulfur (S).

The final essential elements are used in small quantities by the plant, but nevertheless are necessary for plant survival. These micronutrients include iron (Fe), boron (B), copper (Cu), chlorine (Cl), Manganese (Mn), molybdenum (Mo), zinc (Zn), cobalt (Co), and nickel (Ni).

The table below lists the essential elements, their status as macro- or micronutrients, their uptake forms, and their plant mobility.

Nutrient

Macro/micro

Uptake form

Mobility in Plant

Mobility in Soil

Carbon

Macro

CO2, H2CO3

 

 

Hydrogen

Macro

H+, OH-, H2O

 

 

Oxygen

Macro

O2

 

 

Nitrogen

Macro

NO3-, NH4+

Mobile 

Mobile as NO3-, immobile as NH4+

Phosphorus

Macro

HPO42-, H2PO4-

Somewhat mobile

Immobile

Potassium

Macro

K+

Very mobile

Somewhat mobile

Calcium

Macro

Ca2+

Immobile

Somewhat mobile

Magnesium

Macro

Mg2+

Somewhat mobile

Immobile

Sulfur

Macro

SO4-

Mobile 

Mobile

Boron

Micro

H3BO3, BO3-

Immobile

Very mobile

Copper

Micro

Cu2+

Immobile

Immobile

Iron

Micro

Fe2+, Fe3+

Immobile

Immobile

Manganese

Micro

Mn2+

Immobile

Mobile

Zinc

Micro

Zn2+

Immobile

Immobile

Molybdenum

Micro

MoO4-

Immobile

Somewhat mobile

Chlorine

Micro

Cl-

Mobile 

Mobile

Cobalt

Micro

Co2+

Immobile

Somewhat mobile

Nickel

Micro

Ni2+

Mobile 

Somewhat mobile