Transcript No Slide Title

Plant Nutrition
January 2008
Andrew G. Ristvey
Wye Research and Education Center
Maryland Cooperative Extension
College of Agriculture and Natural Resources
University of Maryland
Plant Nutrition
Master Gardener Program
Objectives for this topic include:
* The essential macro and micronutrients necessary for plant growth
and the basic mechanisms for availability and uptake of nutrients.
* Organic and inorganic fertilizers and how they are used by the plant.
* The negative effects of over-applied or mis-applied fertilizers.
* Appropriate timing of fertilizer application and fertilization for
special situations
Growth Factors:
What do plants need to grow?
1.
2.
3.
4.
5.
6.
What is an essential plant nutrient?
All the nutrients needed to carry out growth and
reproductive success; full life cycle
The criteria for essentiality: Arnon and Stout, 1939
1. Omission of the element will result in abnormal growth
2. The element cannot be replaced or substituted
3. The element must exert its effect directly on growth
What is an essential plant nutrient?
There are 17 known (accepted) elements that are
essential for plant growth
Hydrogen, Oxygen, Carbon – plant gets from air
and water
The other 14 are mineralized elements derived from
soil (or air as in N)
Other nutrients being studied:
Silicon, Cobalt, Aluminum
Relationship between plant growth
and nutrient concentration
• What happens when a nutrient or nutrients
are inadequate in supply?
• Can the concentration of a nutrient be too
high?
What is an essential plant nutrient?
von Liebeg’s ‘Law of the Minimum’
Plant growth progresses to
the limit imposed by the
nutrient in least supply
What is an essential plant nutrient?
von Liebeg’s ‘Law of the Minimum’
Plant growth progresses to the limit
imposed by the nutrient in least supply
tires
chassis
engines
Macronutrients
Micronutrients
Nutrient
%
Nitrogen
1.5
Potassium
1.0
Calcium
0.5
Magnesium
0.2
Phosphorus
0.2
Sulfur
0.1
ppm
Chlorine
100
Iron
100
Manganese
50
Boron
20
Zinc
20
Copper
6
Molybdenum
0.1
Nickel
0.05?
Forms in which nutrients exist
• cation – positively charged ion
• anion – negatively charged ion
• neutral – uncharged
• Plants used the mineralized from of a nutrient
– It does not matter to the plant where it comes from
So which nutrients exist in what form?
Anions
Cations
•
•
•
•
•
•
•
•
•
•
ammonium – NH4+
potassium – K+
calcium – Ca+2
magnesium – Mg+2
iron – Fe+2, Fe+3
zinc - Zn+2
manganese Mn+2, Mn+4
copper – Cu+2
cobalt – Co+2
nickel – Ni +2
•
•
•
•
•
•
nitrate – NO3phosphate – H2PO4- , HPO4-2
sulfate - SO4-2
chlorine – Clborate - H3BO3, H2BO3-, B4O7-2
molybdate – MoO4-2
Factors that affect nutrient uptake
• Getting nutrients to the plant roots
– Nutrients are water soluble
• What factors affect nutrient availability
– pH
– Cation Exchange Capacity
• Colloids (humus, clay)
Getting nutrients to the roots:
Mechanisms for nutrient delivery
• mass flow
– the passive movement of nutrients in soil water
to roots
• diffusion
– the movement of nutrient from regions of high
concentration to regions of low concentration
• root interception
– direct contact of nutrients with roots as roots
grow and explore soil
Getting nutrient to the roots:
Mechanisms for nutrient
delivery
Properties Affecting Nutrient Availability
 Chemical Properties - pH
p = potential or power
H = hydrogen
• pH and hydrogen ion
concentration are inversely
related.
• As pH increases, hydrogen
ion concentration
decreases.
Properties Affecting Nutrient Availability
 Chemical Properties - pH
• Logarithmic scale
pH of 6
has 10x more H+
than pH 7
pH
[H+]
[H+]
1
2
3
10-1
10-2
10-3
.1
.01
.001
4
5
6
10-4
10-5
10-6
.0001
.00001
.000001
7
8
9
10-7
10-8
10-9
.0000001
.00000001
.000000001
Properties Affecting Nutrient Availability
 Chemical Properties - pH
pH affects the availability of nutrients
Properties Affecting Nutrient Availability
 Chemical Properties – Cation Exchange Capacity
CEC
•
•
•
•
•
•
•
•
•
•
Anions
Cations
ammonium – NH4+
potassium – K+
calcium – Ca+2
magnesium – Mg+2
iron – Fe+2, Fe+3
zinc - Zn+2
manganese Mn+2, Mn+4
copper – Cu+2
cobalt – Co+2
nickel – Ni+2
•
•
•
•
•
•
nitrate – NO3phosphate – H2PO4-HPO4-2
sulfate - SO4-2
chlorine – Clborate - H3BO3, H2BO3-, B4O7-2
molybdate – MoO4-2
Growing Media - Chemical Properties
 Chemical Properties - pH
pH affects the availability of nutrients
Negatively charged chemical groups OH- on humic particles
Sometimes associated with Fe and Al in clays
+
H
+
H+
H
H+
H+
H+
+
pH
OH+
H
+
H
H
High or Low ?
H+
H+ H+ OH+
+
+
H
OH+
+
H
H
Low
+
H
H
+
H
H
H+
H+ OHH+ H+ OHH+
+
H
H+
+
H
H+
Growing Media - Chemical Properties
 Chemical Properties - pH
pH affects the availability of nutrients
Negatively charged chemical groups OH- on humic particles
Sometimes associated with Fe and Al in clays
H+
H+
OH-
H+
H+
OH-
OH-
H+
H+
H+
pH
High or Low ?
OH-
OH-
High
Properties Affecting Nutrient Availability
 Chemical Properties – Cation Exchange Capacity
CEC
The ability of a soil or substrate to provide a nutrient reserve
It is all the exchangeable cations the soil or substrate can adsorb
The CEC of a soil depends on colloids and pH
The higher the CEC of a soil the better buffering capacity
Properties Affecting Nutrient Availability
 Chemical Properties – Colloids and CEC
Colloids - very small particles in soil that are
chemically reactive (charged) – humus, clay
+
attracts
Fe++
K+
H+
Mg++
Fe++
H+
H+
Mg++
Mn++
Mg++
Mn++
++
Ca
K+
Growing Media - Chemical Properties
 Chemical Properties - Colloids and CEC
pH affects the availability of nutrients
Example of one scneario:
some nutrients become more available at low pH
Mg++
Fe++
Mn++
OH-
Ca++
Fe++
OH-
OH-
Mn++
Fe++
Mn++ Mg++
OH-
Fe++
Fe++
OH-
Mn++
Growing Media - Chemical Properties
 Chemical Properties – CEC
pH affects the availability of nutrients
H+ ions vie for space, certain ions released becoming available
H+
H+
Fe++
++
H+ Ca
Mn++
H+
H+ H+
OH-
H+ Mn++
pH ≈ 5.8
H+
H+ H+ OH++
+ H+
Mn
+
H
OH
+
H
++
++
H
+
Mn
Fe
H
Ca++ + OHOH+
H
H
+
++
H
+
Mn
H
+
H
++
+
Mn++
Fe
H
H+
Fe++
Properties Affecting Nutrient Availability
 Chemical Properties – Cation Exchange Capacity
CEC
The ability of a soil or substrate to provide a nutrient reserve
Cation Exchange Capacity
Types of Soil Colloids
(cmolc/kg of colloid)
humus
vermiculite
100-300
montmorillonite
60-120
illite
iron oxides
15-40
120-150
0-3*
What’s on the Bag
NPK
10#–-10
# -–#10
N – P2O5 – K2O
1.00 – 0.44 – 0.83
N
–
P
–
K
The Major Players – N and P
• Nitrogen
– NO3- N and NH4+-N or urea
• Phosphorus
– H2PO4--P at pH of 5.0 to 6.5
Nitrogen (N)
– NO3- N and NH4+-N or urea
 utilized for a variety of structural and metabolic compounds
 over half of N in plants is found in the leaves of plants
 between 15 and 30% of that leaf nitrogen goes into the production
of Ribulose 1-5-biphosphate carboxylase or Rubisco
 Nitrogen is very mobile within the plant
Nitrogen (N)
NO3- nitrate
 taken up by plants passively and actively
 uptake increases pH in soil
 best uptake pH range between 4.5 and 6
 nitrate can be stored in plant
 nitrates leach
Nitrogen (N)
NH4+ ammonium
 taken up by plants passively and actively
 decreases pH in soil
 ammonium (ammonia) cannot be stored
 must be assimilated immediately by carbon
 ericaceous species utilize
Phosphorus (P)
H2PO4- -P at pH of 5.0 to 6.5
 High pH, P binds with calcium
 Low pH P, binds with iron
 High P fertilizers do not promote root growth
 Utilized for energy transfer, membrane structure, nucleic acids,
proteins
 Mobile in plant
Nutrient Interactions: Relationships of elemental excess
in growing media to potential nutrient deficiencies in plant tissue.
Element in excess in media
Element possibly deficient
in plant tissue
Nitrogen as ammonium
Potassium, Calcium, Magnesium
Potassium
Nitrogen, Calcium, Magnesium
Phosphorus
Copper, Zinc, Iron
Calcium
Magnesium, Boron
Magnesium
Calcium, Potassium
Sodium
Potassium, Calcium, Magnesium
Manganese
Iron, Molybdenum
Iron
Manganese
Zinc
Manganese, Iron
Copper
Manganese, Iron, Molybdenum
Molybdenum
Copper
Aluminum: this element is not essential and high levels are rare in artificial soils.
High Aluminum will precipitate Phosphorus as Aluminum Phosphate and can
highly reduce short term Phosphorus availability.
Mobility of Plant Nutrients: Mobility of elements in the
plant often defines the location of visual symptoms of nutrient deficiencies
or toxicities:
Very
Mobile
Moderately
Mobile
Limited
Mobility
Nitrogen
Phosphorus
Potassium
Magnesium
Sulfur
Molybdenum
Iron
Manganese
Copper
Chlorine
Zinc
Calcium
Boron
* Most recently matured leaves are the most accurate
leaf sample for nutrient analysis.
Nutrient Form:
Organic or Inorganic?
• Plants used the mineralized form of a nutrient
– It does not matter to the plant where the nutrient comes from,
as all nutrients taken up are in a mineralized form
– See handout on types of organic and inorganic fertilizers
• However adding composted organic matter to your soil
will aid in nutrient availability
– See lesson on soils
Nutrient Form:
Composts and Teas?
• Composts are denatured organic materials
– A true aerobic compost requires 3 things
• Aeration
• Moisture – 40 to 60 %
• A C:N ratio of 30 to 1
• Anaerobic composting – less heat, more break down,
increased humus production, but more noxious gases
• Making teas from composts is easy, however
making a consistent product is not
– Anti-pathogen properties
Foliar Nutrient Application
• Plants use the mineralized form of a nutrient
– The majority of nutrient uptake are via plant roots
– Nutrients can be applied via foliar application
– Foliar application should merely be supplemental
• For most nutrients
– If foliar application is the primary method of nutrition
something is wrong with your soil ! (or roots)
Other Negative Effects of Nutrient Over-application
• Runoff
• Physiological responses
 may affect root growth
e.g. recent evidence shows P does not promote root growth
 may affect flowering
e.g. over application of N and other nutrients may
stimulate vegetative growth as in grapes
• Inappropriate fertilizers
 NO3 is not well utilized by ericaceous species
• Balance your NO3 with your NH4
 good for most plants
Timing of Fertility
• Evidence of periodicity in nutrient uptake in some species
• evidence for opposite shoot growth/root uptake periods
• fall uptake for spring growth
• Lawn care specialists suggest fall fertilization
• Arborist stress fall fertilization of trees and shrubs
• Tree nursery recommendations stress split fertilization
early spring and mid summer
• Some concern over cold hardiness issues with fall N fertility
Fertility - special situations
• Drought fertility
 Water is the most important growth regulator
 No water, no growth regardless nutrients
 Fertilizing under drought conditions is not recommended
 High EC’s in soil can damage roots
• New Plantings
 Recent recommendation discourage fertility with new plantings
? What condition (nutrient reserve) were the plants in at purchase
 Watering is more important
Suggested Readings
Growing Media for Ornamental Plants and Turf.
Handrek, K and N. Black. Uni. of New South Wales Press
ISBN 0 86840 333 4
Where does the Nitrogen go ?
Drip
13 g N
63%
• Both Liquid and CRF
?
13%
15%
Runoff
1%
Substrate
Plant
8%
Pruning
Plant Uptake
Efficiency
21%
holly data, 2001
Where does the Nitrogen go ?
33 g N
Overhead Irrigation
Both CRF and Liquid Feed
?
69%
5%
22%
Runoff
3%
1%
Substrate
Plant
Pruning
Take home message – great microbial competitiion
for N
Holly data, 2001
Plant
Uptake
Efficiency
8%
Fertility - special situations
• Mycorrhizal Symbiosis
 Fungal infection creates a mutualistic relationship with plant
 Ectomycorrhizal and Endomycorrhizal (more common)
 Very useful to the plant under conditions of low fertility
 High fertility retards rate of infection
 Fungal mycelia are smaller, have greater surface area than
plant roots
 Potential disease resistance, drought resistance via symbiosis
 Mycorrihzae take C compounds from plant… initially slows
growth … eventual long term benefits
N Fertility Recommendations
(Turf)
• N Fertilizer plan considerations
– what types of N should be applied
– annual N application rates
– application timing
N Fertility Recommendations
(Turf)
• N Fertilizer - types
– All soluble or mixed with slowly available
– nitrate, ammonium or both
– turf uses mainly nitrate (NO3)
 nitrate taken up within 3 days of application
 leaching potential high for nitrate
 should not use in areas that are leaching prone
 should use a 50% WIN formula
N Fertility Turf Recommendations
• N Fertilizer – rate issues
– how much to apply per application
– how much to apply per year
• N Fertilizer Recommendations
– all soluble – no more than 1 lbs per 1000 sq.ft
– nitrate, ammonium or both
– can increase rate if you have S.R. N, but only
up to the annual max rate
N Fertility Turf Recommendations
Years 1-2
Cool Season Grasses
Kentucky bluegrasses
Turf-type tall fescue
Fine fescue
Perennial Ryegrass
Warm Season Grasses
Bermudagrass
Zoysiagrass
Subsequent Years
3.0 - 4.5
3.0 - 4.0
1.0 - 3.0
3.0 - 4.0
3.0 - 4.0
2.0 - 3.0
0.0 - 2.0
3.0 - 4.0
3.0 - 4.0
1.0 - 3.0
3.0 - 4.0
0.0 - 2.0
Table 1. Nitrogen Recommendations for Commercially Maintained Turfgrass on Sites
Total Nitrogen Annually (lbs. N/1000 ft2)
 adjust if mulching or in low traffic areas
N Fertility Turf Recommendations
Recommended
Periods
Periods to Avoid
Warm Season
Grasses
1 month before
dormancy breaks
through Sept. 1st
September 1st through
1 month before dormancy
breaks
During severe or prolonged
drought
Cool Season
Grasses
1 month before top
growth starts through
early June
Late August through 6
weeks after first killing
frost
Mid-June through midAugust
When turf is dormant
due to heat, drought, or
cold
Table 2. Recommended Periods for N Fertilization of Turf Areas.
P Fertility Turf Recommendations
• P Fertilizer – rate issues
– Unlike N, based on soil test results
– P is not needed in large quantities
• P Fertilizer Recommendations
– before soil test results
– no more than 1 lbs P2O5 per 1000 sq.ft
Soil Testing
• Performed at least every 3 years
– the analysis is as good as the sample
– useful tool, different extraction methods
– in Maryland, test results converted to FIV
– Low, Medium, Optimum - Excessive
– gauge P and K fertility on these values
P Fertility Turf Recommendations
FIV Soil Test Category
lbs of P2O5 per 1000 sq/ft
Low
0-25
2.0
Medium
26 - 50
1.0
Optimum - Excessive
51-100, >100
0.0
Table 3. Phosphate Recommendations for Maintenance of
Turf Sites Based on FIV Soil Test Results
Soil Testing
• Performed at least every 3 years
– the analysis is as good as the sample
• Sampling
– divide area into similar soils, slopes, history
– scrape surface litter, sample 4 inches down
– take at least 15 random cores
– mix samples in clean bucket
– fill sample bag 1/3 to 1/2 full
Soil Testing
• Interpreting analysis
– Converting lab values to FIV
• Conversion to FIV
– conversion depends on Lab
– each lab has its own analysis
– one value (FIV) is needed for fertility
recommendations
Soil Testing
To determine an equivalent Maryland FIV value for each soiltest nutrient, multiply the regional laboratory reported value,
expressed in the units shown, by the value in column A and
then add the value in column B.
Example: A soil-test report from A & L Laboratories contains
the following data:
Phosphorus, Bray P1
29 ppm
86 ppm
P-FIV (86 x 1.69) + 6 = 151
P Fertility Turf Recommendations
FIV Soil Test Category
lbs of P2O5 per 1000 sq/ft
Low
0-25
2.0
Medium
26 - 50
1.0
Optimum - Excessive
51-100, >100
0.0
55
151
Table 3. Phosphate Recommendations for Maintenance of
Turf Sites Based on FIV Soil Test Results
Nitrogen (N)
Symptoms of Deficiency and Toxicity
 Deficiency
- occurs in oldest leaves first
- stunted growth yellowing, chlorosis, stunted growth,
leaf drop, increased root shoot ratio
 Toxicity
- occurs with ammonium only
- yellowing, chlorosis, root death
- interactions with K, Ca, Mg
Phosphorus (P)
Symptoms of Deficiency and Toxicity
 Deficiency
- occurs in oldest leaves first
- older leaves darken and turn purple, leaf margin necrosis,
low production of flowers, fruit and seed
 Toxicity
- mostly interactions with other nutrients including
zinc, copper and iron
Potassium (K)
K+
 Like phosphorus, potassium exists as many forms in soils, and
much of it is unavailable to plants,
 Plants take up potassium in large amounts compared to other
nutrients. Only the demand for nitrogen is greater. In plant
tissue the N:K ratio is close to 1:1.
 Maintains a variety of plant metabolic activity mainly by
regulating water status and stomatal control.
 Aides in carbohydrate transport and cellulose production.
 Mobile in plant
Potassium (K)
Symptoms of Deficiency and Toxicity
 Deficiency
- occurs in oldest leaves first
- yellowing of margins and tips of leaves
- edge “scorch”
 Toxicity
- mostly interactions with other nutrients including
calcium and magnesium
Sulfer (S)
SO4-2
 In soil, the majority of sulfur is found in organic form and to a
lesser extent mineral form as sulfates
 Plant roots actively take up sulfur primarily as sulfates SO4 -2,
 Plants utilize sulfur in amino acids, proteins, vitamins and other
plant compounds like glycoside oils that give onions and mustards
their characteristic flavors..
 Sulfur also activates certain enzyme systems
 Not Mobile in plant
Sulfur (S)
Symptoms of Deficiency and Toxicity
 Deficiency
- occurs in youngest leaves first
- similar to N deficiency
 Toxicity
- There are rarely issues of toxicity
Calcium (Ca)
Ca 2+
 Free calcium is loosely bound to organic and mineral colloids
 Calcium is taken up passively in roots tips and moves
through the plant primarily via the xylem during
evapotranspiration
 Mainly found in the cell walls
 Calcium is required for the extension of cell walls during cell
growth at shoot and root tips and enhances pollen tube growth.
 Responsible for membrane stability and cell wall integrity
 Not Mobile in plant
Calcium (Ca)
Symptoms of Deficiency and Toxicity
 Deficiency
- Occurs in youngest leaves first
- Reduction of growth at meristems
- Deformed and chlorotic leaves
- leag margin necrosis
 Toxicity
- mostly interactions with other nutrients including
magnesium, potassium causing deficiencies
Magnesium (Mg)
Mg 2+
 Magnesium is made available to the plant through exchange
with soil colloid complexes
 Plants take-up magnesium passively, transported mainly through
the phloem
 Fifteen to twenty percent of the magnesium in plants is found in
the pigment molecule, chlorophyll.
 Cofactor for enzymes that help transfer energy and CO2 fixation
 Assists in RNA translation for protein synthesis
 Mobile in plant
Magnesium (Mg)
Symptoms of Deficiency and Toxicity
 Deficiency
- Deficiency symptoms appear in older leaves as interveinal
chlorosis.
 Toxicity
- There is typically no magnesium toxicity.
Chlorine (Cl)
Cl  Chlorine naturally occurs in soils as constituents of many soil
minerals and is made available through natural weathering.
 Taken actively and passively depending on soil concentrations,
active when low and passive when concentrations are high
 Utilized in several processes of photosynthesis.
 Mobile in plant
Chlorine (Cl)
Symptoms of Deficiency and Toxicity
 Deficiency
- Deficiencies are uncommon
 Toxicity
Yellowing and burning of leaf tips, with interveinal areas
being bleached, scorched and necrotic in severe cases.
Iron (Fe)
Fe 2+
 Iron is ubiquitous in many soils, yet availability depends on
soil chemistry.
 Actively taken up by the plant and is transported by xylem
to the leaves.
 Utilized in several processes of photosynthesis.
 Not mobile in plant
Iron (Fe)
Symptoms of Deficiency and Toxicity
 Deficiency
- Iron deficiency is similar to magnesium deficiency
symptoms (interveinal chlorosis), but occurs on youngest
leaves first
 Toxicity
- iron interferes with manganese uptake manganese
deficiency (mottled yellowing between veins developing
as necrotic lesions later), as.
Manganese (Mn)
Mn 2+
 Availability depends on pH and organic colloid content.
Increased in low pH
 In the plant manganese is transported in the xylem and delivered
to mertistematic tissue where it is largely immobilized.
 Cofactor for many metabolic enzymes and is important factor
in photosynthesis. Used to split water.
 Not mobile in plant
Manganese (Mn)
Symptoms of Deficiency and Toxicity
 Deficiency
- Interveinal chlorosis, similar to iron and zinc.
 Toxicity
- Toxicity varies among species.
- Occurs in acid soil conditions when manganese is most
available
- Dark purple or brown spots within the leaf margins and/or
leaf tip necrosis
- Toxicity varies among species. Plants associated with acid
soils are naturally tolerant to high manganese conc.
- Severe toxicity results in stunted and yellowed meristems.
Boron (B)
H3BO3
 Availability depends on pH and organic colloid content.
Increased in low pH
 Boron moves into the plant, passively taken up in solution by the
roots via evapotranspiration, moving through xylem
 Factor in cell growth, including division, differentiation, and
elongation
 Cell processes like carbohydrate metabolism and other
metabolic pathways
 Concentrated at growth areas including reproductive structures.
 Not mobile in plant
Boron (B)
Symptoms of Deficiency and Toxicity
 Deficiency
- Since boron is associated with cell growth, deficiencies
usually show up in new growth as wrinkled and withered
leaves, with tip death soon after.
- Like calcium, deficiencies may be caused by drought or
high humidity.
 Toxicity
- Toxicity can develop quickly, the range between deficient
and toxic supply is small.
- Different tolerances among plant species.
- Yellowing of the leaf tips, interveinal chlorosis and leaf
margin scorching.
Copper (Cu)
Cu 2+
 Optimally available in slightly acid conditions where the copper
ion exchanges with other cations on soil colloids
 Root uptake is active and copper moves in the xylem, complexed
with amino acids and other nitrogenous compounds.
 Copper is utilized with enzymes for metabolic activities and
photosynthesis.
 Not mobile in plant
Copper (Cu)
Symptoms of Deficiency and Toxicity
 Deficiency
- Deficiencies of copper show up on the youngest leaves
first
- Depressed and twisted growth
- New leaves appear pale along the margins but green at the
end of the veins.
- Spotty necrosis occurs in the leaf margins. Stems may
become distorted and twisted.
 Toxicity
- Toxic levels of cooper induce iron deficiency and
accompanying symptoms along with depressed root
growth.
Molybdenum (Mo)
MoO4 -2
 Molydenum uptake is dependent on solubility of the ion. Unlike
many micronutrients, molybdenum becomes more available in
higher pH.
 In the leaf, used for an important enzymatic process called nitrate
reduction, the first of two important physiological steps that
make nitrate usable in the plant
Relatively mobile in plant
Molybdenum (Mo)
Symptoms of Deficiency and Toxicity
 Deficiency
- Since molybdenum is essential for nitrate reduction, a
deficiency in molybdenum manifests as a nitrogen
deficiency
- leaf chlorosis in older leaves
- then leaf margin wilting
- leaf and meristem death
 Toxicity
- rare in soils and plants can tolerate relatively high levels of
molybdenum
Zinc (Zn)
Zn +2
 present in sulfide and silicate minerals and is also associated
with organic colloids
 Zinc is actively taken up by plants and transported through the
xylem
 metabolic functions including auxin (growth hormone)
production, a cofactor in protein synthesis, enzyme activity and
carbohydrate metabolism and regulation.
 chlorophyll production
 may enable plants to tolerate colder temperatures
 Slightly mobile in plant, mainly stored in roots
Zinc (Zn)
Symptoms of Deficiency and Toxicity
 Deficiency
- Symptoms on older leaves first
- Include interveinal chlorosis, curled and dwarfed leaves
and then leaf scorch and necrosis.
- excessive phosphorus can interfere with zinc uptake
 Toxicity
- May occur in low pH soils (< pH 5) or where municipal
sludge has been added to soils
- Toxicity concentrations are species dependent
- interfere with iron uptake
Nickel (Ni)
Ni +2
 Nickel is the newest recognized essential plant nutrient
 requirement was not known because impurities in
irrigation water and fertilizers supplied the very low
requirements of this nutrient
 required for the enzyme urease to metabolize urea, releasing
the ammoniacal nitrogen for plant use
 for iron absorption and seeds production and germination
 evidence to suggest that carbon respiration and nitrogen
metabolism are sensitive to Ni nutrition
 Possibly mobile in plants
Nickel (Ni)
Symptoms of Deficiency and Toxicity
 Deficiency
- rounded, blunt and slightly curled leaves known as
“mouse-ear”
- seen on spring growth and is a result of accumulation of
urea to the point of toxicity
 Toxicity
- At a level of 100 ppm or higher, nickel is considered to be
phytotoxic
- toxicities typically exist in areas where industrial waste has
been concentrate
- In beets severely stunted growth; young leaves at early
stage show chlorotic iron deficiency symptoms, followed
by severe necrosis, collapse and death