Download Lab 12

NUTRIENT DEFICIENCY SYMPTOMS IN PLANTS
Laboratory Exercise #12
OBJECTIVES

Know the definition of element, compound, macronutrient and micronutrient.

Know the 17 essential nutrient elements.

Learn how to use the "Key to Nutrient Disorders ".
INTRODUCTION
Plants need at least 17 different chemical elements to grow. An element is a pure chemical that
contains only one type of atom. Examples of common elements include iron, hydrogen, oxygen,
nitrogen and carbon. Calcitic and dolomitic lime is examples of compounds. These substances
consist of several elements bound together (e.g. CaCO3 or CaMg(CO3)2. Most minerals are
compounds containing specific elements.
The 17 elements required by plants are obtained from the soil, water and air. Fourteen of these
elements must be supplied by the soil. Six of the soil elements required by plants are needed in
relatively large amounts and are usually added to the soil through fertilizer or lime. These elements
are termed macronutrients. The remaining 8 elements supplied by soil are required in very small
amounts and are termed macronutrients. These elements are usually added as fertilizers because
the soil is not always able to supply the amounts needed by plants. Table 1 lists the 16 essential
plant elements and their chemical symbol. MEMORIZE ALL THESE ELEMENTS AND THE
CHEMICAL SYMBOLS.
Nutrient deficiency symptoms usually appear on the plant when one or more nutrients are in short
supply. It is important to note the forms in which nutrients are taken up by the plant (Table 2). In
many cases, deficiency may occur because an added nutrient is not in the form the plant can use.
Deficiency symptoms for specific elements are included on the "Key to Nutrient Disorders". Every
soil is not susceptible to the same nutrient deficiencies. For example, coarse-textured soils low in
organic matter is susceptible to sulfur deficiencies whereas sulfur is usually in adequate supply in
clayey soils or soils high in organic matter. Table 3 lists the soil conditions that lead to
deficiencies of specific elements.
Some crops are more susceptible to deficiencies of micronutrients than other crops. Listed in
Table 4 are 6 micronutrients and the common plants that are susceptible to deficiencies in these
elements.
Table1. Essential nutrient elements and their source
Macronutrients
Air and Water
Soil
Carbon
C
Hydrogen H
Oxygen O
Micronutrients
Soil
Nitrogen
Phosphorus
Potassium
Calcium
Magnesium
Sulfur
N
P
K
Ca
Mg
S
Iron
Manganese
Boron
Molybdenum
Copper
Zinc
Chlorine
Nickel
Fe
Mn
B
Mo
Cu
Zn
Cl
Ni
Table 2. Forms of nutrients used by plants
Macronutrients
Macronutrients
Nutrient
Symbol
Form Used by Plant
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
Potassium
Calcium
Magnesium
Sulfur
C
H
O
N
P
K
Ca
Mg
S
CO2
H2O
H2O
NH4+ & NO3 H2PO4 & HPO42K+
Ca2+
Mg2+
SO42-
Iron
Manganese
Boron
Molybdenum
Copper
Zinc
Chlorine
Fe
Mn
B
Mo
Cu
Zn
Cl
Fe2+
Mn2+
H2B03MoO42Cu2+
Zn2+
Cl-
Cobalt
Silicon
Sodium
Vanadium
Co
Si
Na
V
Co2+
Si(OH)4
Na+
V
Beneficial Nutrients§
§ May enhance the growth of some plants
Table 3. Soil factors that may lead to deficiencies of selected nutrients.
Element(s)
Soil Factor Resulting in Deficiency
N&K
Excessive leaching on coarse-textured low organic matter soils
P
1. Acid low organic matter soils
2. Cold wet soils such as occurs during early spring
3. Newly cleared soils
S
Excessive leaching on coarse-textured low organic matter soils in areas
where air pollution is low (minimal levels of SO2 in the air)
Ca & Mg
1. Excessive leaching on coarse-textured low organic matter soils 2.
Soils where large amounts of K have been applied
Fe
1. Poorly drained soils
2. Low organic matter soils, pH>7.0
3. Soils high in P
Zn
1. Cold wet soils low in organic matter and highly leached
2. High pH soils (pH>7.0)
3. Soils high in P
4. Exposed subsoils
Cu
1. Peat and muck soils
2. High pH, sandy soils
3. Soils heavily fertilized with N
B
1. Excessive leaching on coarse-textured low organic matter soils
2. Soils with pH>7.0
Mn
1. Excessive leaching on coarse-textured low organic matter soils
2. Soil with pH>6.5
Mo
1. Soils high in Fe oxides, high adsorption of molybdenum
2. Soil cropped for a long time
NOTE: Soil testing and plant tissue analysis should be done to determine which nutrients are
needed and how much of each should be applied. Excessive applications of the following
micronutrients may lead to toxicities: B, Cu, Fe, Mn and Zn.
Table 4. Crops most likely to show micronutrient deficiencies.
Micronutrient
Susceptible Crop
Mn
Soybean, Small Grain & Peanuts
Cu
Wheat & Corn
Zn
Corn
Mo
Soybeans & Cauliflower
B
Alfalfa, Apples, Peanuts, Tobacco & Tomatoes
Fe
Ornamentals, Fruit Trees, Soybeans, Grain Sorghum & Some Grasses
SLIDE SHOW
The purpose of this lab is to become familiar with nutrient deficiencies in
crops. When you see these symptoms on your own plants, you should get the soil
tested to determine which nutrient is deficient and how much nutrient must be added
to the soil to correct the problem. Take notes about the various deficiencies you
observe in the slide show. Be prepared to identify the five unknown deficiencies
shown at the end of the slide show. You may use the Key to Nutrient Disorders
provided below.
KEY TO NUTRIENT DISORDERS
NITROGEN: General chlorosis. Chlorosis progresses from light green to yellow. Entire plant
becomes yellow under prolonged stress. Growth is immediately restricted and plants soon
become spindly and drop older leaves.
PHOSPHORUS: Leaves appear dull, dark green, blue green, or red-purple, especially on the
underside, and especially at the midrib and vein. Petioles may also exhibit purpling. Restriction in
growth may be noticed.
POTASSIUM: Leaf margins tanned, scorched, or have necrotic spots (may be small black
spots which later coalesce). Margins become brown and cup downward. Growth is restricted
and die back may occur. Milder symptoms appear first on recently matured leaves, then
become pronounced .on older leaves, and finally on younger leaves. Symptoms may be more
common late in the growing season due to translocation of K to developing storage organs.
CALCIUM: Growing points usually damaged or dead (die back). Margins of leaves
developing from the growing point are first to turn brown.
MAGNESIUM: Marginal chlorosis or chlorotic blotches which later merge. Leaves show
yellow chlorotic interveinal tissue on some species, reddish purple progressing to necrosis on
others. Younger leaves affected with continued stress. Chlorotic areas may become necrotic,
brittle, and curl upward. Symptoms usually occur late in the growing season.
SULFUR: Leaves uniformly light green, followed by yellowing and poor spindly growth.
Uniform chlorosis does not occur.
COPPER: Leaves wilt, become chlorotic, then necrotic. Wilting and necrosis are not
dominant symptoms.
IRON: Distinct yellow or white areas appear between veins, and veins eventually become
chlorotic. Symptoms are rare on mature leaves.
MANGANESE: Chlorosis is less marked near veins. Some mottling occurs in interveinal areas.
Chlorotic areas eventually become brown, transparent, or necrotic. Symptoms may appear later
on older leaves.
ZINC: Leaves may be abnormally small and necrotic. Internodes are shortened.
BORON: Young, expanding leaves may be necrotic or distorted followed by death of
growing points. Internodes may be short, especially at shoot terminals. Stems may be rough,
cracked, or split along the vascular bundles.
Study Questions
1. List the macronutrients which are supplied by the soil?
2. List the macronutrients which are not supplied by air and water?
3. List the micronutrients and their source?
3. What is the difference between macro and micronutrients?
4. In what form are nutrients taken up by plants?
5. Explain the role of pH and nutrient availability?
7. Many nutrients are mobile in the plant, how can you tell if the plant is deficient in
mobile nutrients?
8. Other nutrients are not mobile, how can you tell if a plant is deficient in non-mobile
nutrients?