Trace ElementsTrace Elements

Trace Elements

• Required in low amounts by plants Copper (Cu)q y p

• Essential for healthy growth

• Difficult to pick up in soil tests due to low 

Copper (Cu)

Iron (Fe)

M (M )quantities in soil– Eg Zinc <0.75 mg/kg may be a critical level

– Chemically difficult to measure

Manganese (Mn)

Zinc (Zn)– Chemically difficult to measure

– Low therapeutic index (low value close to normal or toxic eg Boron)

Boron (B)

Molybdenum (Mo)

• Often by association– Soil pH

– Waterlogging

Chloride

NickelWaterlogging

– Soil type (geology) Silicon

Micronutrient Contents in Soilsand Crop Removal

Estimated crop removal, kg/ha

Range in soils, Corn Cotton Nutrient total, kg/ha 10 t/ha 2.5 t/ha lint

Boron 20 200 0 06 0 05Boron 20-200 0.06 0.05Copper 2-400 0.05 0.03 Iron 10,000-

200 0000.10 0.07

200,000Manganese 100-10,000 0.08 0.30 Molybdenum 1-7 0.03 0.02 Zi 20 600 0 15 0 06Zinc 20-600 0.15 0.06

Soil pH and nutrient availabilityp y

• Soil acidity (pH) drives much of y (p )the chemisty in the soil

• Reactions to free to bind i d i b il Hnutrients driven by soil pH

• Liming will change micronutrient availabilitymicronutrient availability

• Deficiency and toxicity (eg B and Mn)

• Classic deficiencies– Zinc and iron on alkaline soils

M l bd id il– Molybdenum on acid soils

Availability of trace elements

• Factors influencing availability of micronutrients in soils

y

g y

Cu Fe Mn Zn B Mo

pH > 7.0 --- --- -- --- ** ++pH < 5.5 ++ +++ +++ + -- --

t l d il + + +water-logged soil + -- + +drought --- --- --- - --- --high humus content --- ++ ++ ++ ++ -high P-content - --- - --- - +++high P-content - --- - --- - +++sand --- --- -- --- -- -compaction + ++ + + + +

--- low availability high +++

Mulders Graph – complexity of interactions among t i tnutrients

Examplesp

• High sulphur– Low selenium (animal issue)

– Reduces zinc accumulation

• High K• High K– Reduces Mg uptake

Demand and uptake by plantsp y p

• Fruit trees with special susceptibility for deficiency:p p y y

Cu Fe Mn Zn B Mo

Citrus ++ +++ +++ +++ +++Citrus ++ +++ +++ +++ +++

Apple / Pear ++ ++ +++ +++ +++

Apricot +++ +++ +++

Peach +++ +++ +++

Strawberry ++ +++ +++

Melon +++ +++ +++Melon +++ +++ +++

Grapevine ++ +++ +++ +++ ++

Hazelnut +++

Diagnosing trace element deficienciesg g

• Nutrient mobilityy

• Determines if seen in older or younger leaves

• Symptoms in older leaves occur with mobile nutrients (egmobile nutrients (egNitrogen)

• Symptoms in younger leaves occur with less mobile nutrients (egSulphur)p )

Fe deficiency Young leaves become y gyellow, but their veins remain green. Leaves may loose all pigments and turn white laterand turn white, later necrotic.

Fe deficiency in grain sorghum

Factors which Can Contributeto Iron Deficienciesto Iron Deficiencies

• Imbalance with metals such as Mo, Cu and Mn

• Excessive soil P• Wet, cold soils• High soil pH• High soil bicarbonate levels• Plant genetic differences• Low soil organic matter

Iron Fertilizer SourcesIron Fertilizer Sources

Source % Fe Iron sulfates 19-23Iron oxides 69-73 I i lf 14Iron ammonium sulfate 14Iron ammonium polyphosphate 22 Iron chelates 5 14Iron chelates 5-14Other organics 5-10

Zn deficiencyySimilar to Fe-deficiency, leaves are small; twigs are stunted ; gand rosette-like. Poor flowering and fruiting.

Some Plant Functions of ZincSome Plant Functions of Zinc• Aids in the synthesis of enzyme systems

P i b li f i• Promotes certain metabolic functions• Necessary for the production of chlorophyll

d b h d tand carbohydrates

Zn deficiencyiin corn

Factors and ConditionsAffecting Zinc Availability

• Soil texture and pH • Leachingp• Soil phosphate

levels

g• Cold, wet soils• Soil biological• Soil organic matter

• Leveling for irrigation

Soil biological activity

irrigation

Zinc Fertilizer Sources

Source % Zn

Zinc sulfates (hydrated) 23-36Zinc oxide 78 Basic zinc sulfate 55Basic zinc sulfate 55Zinc-ammonia complexes 10 Zinc chelates 9-14 Other organics 5-10

B deficiencyyLeaf chlorosis or yellow spots, smaller leaves with a hard leaf texture. Stems and leaves distorted. Malformed fruits with stone cells (often in pear fruits)fruits).

Boron deficienciesare widespread in many

parts of the world

Some Roles of Boron in Plants ‐E ti lEssential:

• In germination of pollen grains• For growth of pollen tubes• For seed and cell wall

formation• For protein formation• For sugar translocation

Boron Deficiency Symptomson Cropson Crops

Celery Crooked stemPeanuts Hollow heartApples Corky coreAlfalfa Rosetting yellow top death of terminalAlfalfa Rosetting, yellow top, death of terminal

budBeets Black heartCotton Ruptured squares, dieback of terminal

bud, rosetting

B d fi iB d fi iB deficiencyB deficiencyon peanutson peanuts

B B

on peanutson peanuts

deficiencydeficiencylf lflf lfon alfalfaon alfalfa

Responsiveness of Crops to BoronMost response Medium response Least response

AlfalfaCauliflower

C l

BroccoliCabbage

BeansBlueberries

CelerySugarbeetsTable beets

CarrotsLettuce

CucumbersCorn

TurnipsPeanutsCotton

SpinachSweet cornTomatoes

OnionsPotatoes

Small grainsCottonApplesClover

TomatoesAsparagus

Canola

Small grainsSorghum

Sudan grassCanolaRadish

Sudan grassSoybeans

Factors Affecting Boron Availability

• Organic matterOrganic matter• Weather conditions• Soil pH• Soil pH• Soil texture• Leaching• Leaching

Boron Fertilizer Sources

Boron, Water Source % soluble Borax 11.3 Yes Sodium pentaborate 18.0 Yes Sodium tetraborateSodium tetraborate Fertilizer Borate 46 14.0 Yes Fertilizer Borate 65 20.0 Yes Boric acid 17 0 YesBoric acid 17.0 YesColemanite 10.0 Low Solubor 20.0 Yes

Boron Reduces Barren Stalksand Increases Corn Yieldand Increases Corn Yield

Boron rate, Barren stalks Yield, lb/A % bu/A

0 23 1480 23 1481 27 161 2 19 1704 18 164

Mn deficiencyySimilar to Fe-deficiency, but veins have a green seamhave a green seam, chlorotic interveinal areas turn pale-green to yellow, sometimes necrotic spots.

Functions of Manganesein the Plantin the Plant

• Part of the plant enzyme systemA i l b li i• Activates several metabolic reactions

• Aids in chlorophyll synthesis• Accelerates germination and crop maturity• Increases plant availability of P and Ca

Mn deficiency in soybeansy y

S C f MSome Causes of Manganese Deficiency

• High soil pH• Imbalance with other nutrients such as Ca• Imbalance with other nutrients such as Ca,

Mg and Fe• Soil moistureSoil moisture• High organic matter soils during cool spring

when soils are waterloggedwhen soils are waterlogged

Manganese Fertilizer Sources

Source % Mn

Manganese sulfates 26 28Manganese sulfates 26-28Manganese oxides 41-68 Manganese chelate 12Manganese chelate 12Manganese carbonate 31

Manganese chloride 17Manganese chloride 17

Cu deficiency in wheat

Organic soils are mostOrganic soils are mostlikely to be Cu deficienty

Copper Fertilizer Sources

Copper Water

Source % solubleSource % soluble

Copper sulfate 22.5 Yes

Copper ammonium phosphate 30.0 Slight

Copper chelates Variable Yes

Other organics Variable Yes

N t A li ti th d b f li ilN t A li ti th d b f li ilNote: Application method may be foliar or soilNote: Application method may be foliar or soil

Use Diagnostic Tools to Determine Need for Mi t i t F tili tiMicronutrient Fertilization

S il t ti• Soil testing• Plant analysis

Fi ld d t ti• Field demonstrations• Field observations

Typical Ranges of Micronutrient Concentrations in M t L f TiMature Leaf Tissue

Sufficient ExcessiveSufficient ExcessiveSufficient ExcessiveNutrient Deficient normal or toxic

-------------------- ppm -------------------

Sufficient ExcessiveNutrient Deficient normal or toxic

-------------------- ppm -------------------

Iron <50 100‐500 >500Zinc 10‐20 27‐100 100‐400Zinc 10 20 27 100 100 400Manganese 15‐25 20‐300 300‐500Copper 2‐5 5‐30 20‐100B 5 30 10 200 50 200Boron 5‐30 10‐200 50‐200Molybdenum 0.30‐0.15 0.1‐2.0 >100

Petiole tests

• Eg for vinesg

• Contamination

G th t• Growth stage

• Tissue

Meeting the needg

• As supplements to granular fertilizers– Ease of application, one passpp , p

– Battle against soil chemistry (eg Copper or Iron)

– Protection – Chelating agents eg Fe EDTA

A f li f ili d d bili d d• As foliar fertilizers ‐ depends on ability to meet demandNutrient Nutrient

formConc. in solution

[%]

Nutrient supply [k /h ]

Removal(kg/ha)

SupplyRemoval

[%] [kg/ha]N urea 12 23 200 0.12Fe FeEDTA 0.5 0.3 1.3 0.2

SO OZn ZnSO4 x 7H2O 1 0.9 0.5 1.8Mn MnSO4 x H2O 2 2.6 0.8 3.2Cu CuSO4 x 5H2O 0.5 0.5 0.09 5.7B Na2B4O7 x

10H2O1 0.45 0.07 6.9

Mo Na2MoO4 x 2H2O 0.05 0.08 0.006 13.2

MicronutrientsARE NOTARE NOT

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