Plant Nutrition

1
Plant Nutrition
January 2008
Andrew G. Ristvey Wye Research and Education
Center
Maryland Cooperative Extension College of
Agriculture and Natural Resources University of
Maryland
2
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
3
Growth Factors What do plants need to grow?

• 1.
• 2.
• 3.
• 4.
• 5.
• 6.

4
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

1. The element cannot be replaced or substituted

1. The element must exert its effect directly on
   growth

5
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
6
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?

7
What is an essential plant nutrient?

• von Liebegs Law of the Minimum

Plant growth progresses to the limit imposed by
the nutrient in least supply
8
What is an essential plant nutrient?

• von Liebegs Law of the Minimum

Plant growth progresses to the limit imposed by
the nutrient in least supply
tires
chassis
engines
9
Nutrient ppm
Nitrogen 1.5
Potassium 1.0
Calcium 0.5
Magnesium 0.2
Phosphorus 0.2
Sulfur 0.1
Chlorine 100
Iron 100
Manganese 50
Boron 20
Zinc 20
Copper 6
Molybdenum 0.1
Nickel 0.05?
Macronutrients
Micronutrients
10
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

11
So which nutrients exist in what form?
Anions
Cations

• ammonium NH4
• potassium K
• calcium Ca2
• magnesium Mg2
• iron Fe2, Fe3
• zinc - Zn2
• manganese Mn2, Mn4
• copper Cu2
• cobalt Co2
• nickel Ni 2

• nitrate NO3-
• phosphate H2PO4- , HPO4-2
• sulfate - SO4-2
• chlorine Cl-
• borate - H3BO3, H2BO3-, B4O7-2
• molybdate MoO4-2

12
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)

13
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

14
Getting nutrient to the roots Mechanisms for
nutrient delivery
15
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.

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Properties Affecting Nutrient Availability

• Chemical Properties - pH

pH H H
1 10-1 .1
2 10-2 .01
3 10-3 .001
4 10-4 .0001
5 10-5 .00001
6 10-6 .000001
7 10-7 .0000001
8 10-8 .00000001
9 10-9 .000000001

• Logarithmic scale
• pH of 6
• has 10x more H
• than pH 7

17
Properties Affecting Nutrient Availability

• Chemical Properties - pH

pH affects the availability of nutrients
18
Properties Affecting Nutrient Availability

• Chemical Properties Cation Exchange Capacity

C E C
Anions
Cations

• ammonium NH4
• potassium K
• calcium Ca2
• magnesium Mg2
• iron Fe2, Fe3
• zinc - Zn2
• manganese Mn2, Mn4
• copper Cu2
• cobalt Co2
• nickel Ni2

• nitrate NO3-
• phosphate H2PO4-HPO4-2
• sulfate - SO4-2
• chlorine Cl-
• borate - H3BO3, H2BO3-, B4O7-2
• molybdate MoO4-2

19
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
pH High or Low ?
OH-
OH-
OH-
Low
OH-
OH-
20
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
pH High or Low ?
OH-
OH-
OH-
High
OH-
OH-
21
Properties Affecting Nutrient Availability

• Chemical Properties Cation Exchange Capacity

C E C
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
22
Properties Affecting Nutrient Availability

• Chemical Properties Colloids and CEC

Colloids - very small particles in soil that are
chemically reactive (charged) humus, clay
attracts
Fe
Fe
Mg
K
H
H
H
Ca
Mg
Mg
K
Mn
Mn
23
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
OH-
Fe
Mn
Mn
Fe
OH-
Mg
Fe
OH-
OH-
Mn
Fe
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Growing Media - Chemical Properties

• Chemical Properties CEC

pH affects the availability of nutrients
H ions vie for space, certain ions released
becoming available
Mn
Mn
Fe
pH 5.8
OH-
Ca
OH-
Fe
Mn
OH-
Mn
Fe
Ca
OH-
OH-
Mn
Mn
Fe
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Properties Affecting Nutrient Availability

• Chemical Properties Cation Exchange Capacity

C E C
The ability of a soil or substrate to provide a
nutrient reserve

• Cation Exchange Capacity
• (cmolc/kg of colloid)

• Types of Soil Colloids

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Whats on the Bag
N P K
10 10 10
- -
P2O5
N
K2O
1.00
0.44
0.83


N


P
K
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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

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• 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

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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

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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

32

• 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

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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.
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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 Magnesium Iron
Phosphorus Sulfur Manganese
Potassium Molybdenum Copper
Chlorine Zinc
Calcium
Boron
Most recently matured leaves are the most
accurate leaf sample for nutrient analysis.
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Nutrient FormOrganic 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

36
Nutrient FormComposts and Teas?

• Composts are denatured organic materials
• A true aerobic compost requires 3 things

• Aeration

• Moisture 40 to 60

• A CN 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

37
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)

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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

39
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

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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 ECs 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

41
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

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Where does the Nitrogen go ?
Drip
13 g N
63
?

• Both Liquid and CRF

holly data, 2001
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Where does the Nitrogen go ?
Overhead Irrigation
33 g N
Both CRF and Liquid Feed
?
69
Take home message great microbial competitiion
for N
Holly data, 2001
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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

46
N Fertility Recommendations(Turf)

• N Fertilizer plan considerations

• what types of N should be applied

• annual N application rates

• application timing

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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

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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

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N Fertility Turf Recommendations
Years 1-2 Subsequent Years
Cool Season Grasses Kentucky bluegrasses Turf-type tall fescue Fine fescue Perennial Ryegrass 3.0 - 4.53.0 - 4.01.0 - 3.03.0 - 4.0 3.0 - 4.02.0 - 3.00.0 - 2.03.0 - 4.0
Warm Season Grasses Bermudagrass Zoysiagrass 3.0 - 4.01.0 - 3.0 3.0 - 4.00.0 - 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

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N Fertility Turf Recommendations
Recommended Periods Periods to Avoid
Warm Season Grasses 1 month before dormancy breaks through Sept. 1st September 1st through1 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 mid-August When turf is dormantdue to heat, drought, or cold
Table 2. Recommended Periods for N Fertilization
of Turf Areas.
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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

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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

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P Fertility Turf Recommendations
FIV Soil Test Categorylbs of P2O5 per 1000 sq/ft
Low 0-25 Medium 26 - 50 Optimum - Excessive 51-100, gt100
2.0 1.0 0.0
Table 3. Phosphate Recommendations for
Maintenance of Turf Sites Based on FIV Soil Test
Results
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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

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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

56
Soil Testing
To determine an equivalent Maryland FIV value for
each soil-test 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
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86 ppm
P-FIV (86 x 1.69) 6 151

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P Fertility Turf Recommendations
FIV Soil Test Categorylbs of P2O5 per 1000 sq/ft
Low 0-25 Medium 26 - 50 Optimum - Excessive 51-100, gt100
2.0 1.0 0.0
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151
Table 3. Phosphate Recommendations for
Maintenance of Turf Sites Based on FIV Soil Test
Results
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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

60
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

61

• 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 NK ratio is close to 11.

• 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

62
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

63

• 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

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Sulfur (S)
Symptoms of Deficiency and Toxicity

• Deficiency
• - occurs in youngest leaves first
• - similar to N deficiency

• Toxicity
• - There are rarely issues of toxicity

65

• 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

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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

67

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

68
Magnesium (Mg)
Symptoms of Deficiency and Toxicity

• Deficiency
• - Deficiency symptoms appear in older leaves as
  interveinal chlorosis.

• Toxicity
• - There is typically no magnesium toxicity.

69

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

70
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.

71

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

72
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.

73

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

74
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.

75

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

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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.

77

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

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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.

79

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

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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

81

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

82
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 (lt pH 5) or where
  municipal
• sludge has been added to soils
• - Toxicity concentrations are species dependent
• - interfere with iron uptake

83

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

84
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