Knowing nutrient mobility is helpful in diagnosing plant nutrient deficiencies

Nutrients important for plant growth vary in their ability to move within the plant. Knowing how they move can be helpful when diagnosing deficiency problems.

Seventeen elements have been identified as vital to plant growth. Three elements, carbon, hydrogen and oxygen, are non-minerals and the other 14 (Table 1) are minerals. Carbon and oxygen enter plants through leaves as carbon dioxide. Oxygen also enters plants with hydrogen through roots as water. The other 14 must be dissolved in soil water and enter the plant as roots take up water. Mineral elements can further be divided into primary or secondary macronutrients and micronutrients. Macronutrients are those needed in relatively large amounts while micronutrients, as their name implies, are needed in small amounts. However, a deficiency in any vital element can seriously inhibit plant development.

Table 1. The 14 elements essential for plant growth and their mobility and role within the plant.

Macronutrients

Symbol

Mobile in plant

Role in plant

 Primary

 Nitrogen

N

Yes

Formation of amino acids, vitamins and proteins; cell division

 Phosphorous

P

Yes

Energy storage and transfer; cell growth; root and seed formation and growth; winter hardiness; water use

 Potassium

K

Yes

Carbohydrate metabolism, breakdown and translocation; water efficiency; fruit formation; winter hardiness; disease resistance

 Secondary

 Calcium

Ca

No

Cell division and formation; nitrogen metabolism; translocation; fruit set

 Magnesium

Mg

Yes

Chlorophyll production; phosphorus mobility; iron utilization; fruit maturation

 Sulfur

S

No

Amino acids formation; enzyme and vitamin development; seed production; chlorophyll formation

Micronutrients

 Boron

B

No

Pollen grain germination and tube growth; seed and cell wall formation; maturity promotion; sugar translocation

 Chlorine

Cl

Yes

Role not well understood

 Copper

Cu

No

Metabolic catalyst; functions in photosynthesis and reproduction; increases sugar; intensifies color; improves flavor

 Iron

Fe

No

Chlorophyll formation; oxygen carrier; cell division and growth

 Manganese

Mn

No

Involved in enzyme systems; aids chlorophyll synthesis; P and CA availability

 Molybdenum

Mo

Yes

Nitrate reductase formation; converts inorganic phosphates to organic

 Nickel

Ni

Yes

Nitrogen metabolism and fixation; disease tolerance

 Zinc

Zn

No

Hormone and enzyme systems; chlorophyll production; carbohydrate, starch and seed formation

Once inside plants, nutrients are transported to where they are needed, typically to growing points. Once incorporated by the plant, some elements can be immobile while others can be remobilized. Immobile elements essentially get locked in place and that is where they stay. Those that can be remobilized can leave their original location and move to areas of greater demand. Knowing which are mobile or immobile is helpful in diagnosing deficiency symptoms.

Since immobile elements do not easily move within the plant, when deficiency symptoms occur they show up in new growth (Photo 1). When mobile elements become limiting, they can be scavenged from older growth and moved to where they are most needed, causing deficiency symptoms in older growth (Photo 2).

Nutriet deficiency Nutriet deficiency
Photos 1-2. (Left) Typical deficiency symptoms of a non- mobile nutrient (iron) within the plant. Note newer leaves are more affected. (Right) Typical deficiency symptoms of a mobile nutrient (nitrogen) within the plant. Note older leaves are senescing while younger leaves are still green.
Photo credits: Howard F. Schwartz, Colorado State University, Bugwood.org (left) and R.L. Croissant, Bugwood.org (right)

Most nutrient deficiencies need a certain amount of time after growth begins for symptoms to occur. Early growth is often not fast enough or of a great enough volume for symptom expression. Deficiencies are often revealed when the plant is at maximum growth or at other times of high nutrient demand such as fruit development.

According to Michigan State University Extension, nutrient deficiencies can be due to a number of reasons. The most obvious is that the element is not in a high enough level naturally in the soil. Many sand-based soils with high leaching potential are often low in highly soluble nutrients. In some cases, the element is in adequate levels, but unavailable due to pH being too high or too low or the soil temperature being too low for adequate uptake. Other reasons could be too little or too much water or soil compaction. Remember all mineral elements need to come from the soil and if water uptake is interrupted for any reason, so is nutrient uptake.

For additional information on plant nutrients, see:

For more information on commercial vegetable production, contact Ron Goldy at 269-944-1477 ext. 207 or .(JavaScript must be enabled to view this email address).