Micronutrient Management

• Zinc Zn• Iron Fe• Boron B• Copper Cu• Manganese Mn• Molybdenum Mo• Chlorine Cl• Nickel

Eight Essential Nutrients• Minor elements or trace elements• Increased interest in micronutrients

– Higher crop yields and micronutrient removal rates– Declining soil organic matter, a major source of of most

micronutrients– N, P and K fertilizers contain lower amounts of

micronutrient impurities

• Excessive levels can cause toxic effects on plants

• Zn ..Cl….Fe ……. B ….Mg …………Cu, Mn, Ni

Micronutrient Levels in the Soil Surface

Micronutrient

Iron

Manganese

Boron

Chlorine

Zinc

Copper

Molybdenum

Lb/Acre

70,000

1,000

40

20

20

10

2

Organic Matter

• Important source of most micronutrients

• Zn and B deficiencies are more likely to occur in soils low in O.M.

• Deficiencies of Cu and Mn are most common in peat soils

Soil pH• Soil pH affects availability of micronutrients

• In general the solubility and availability of micronutrients are greatest in acid soils and lowest in high pH calcareous soils

• Exception is Mo

• In some soils, high levels of soluble Fe, Al and Mn may be toxic to plants

Soil Conditions and Crops Where Micronutrient Deficiencies Most Frequently Occur

Micronutrient Conditions Most Conducive Susceptible Crops

Zinc (Zn) Exposed subsoils, recently leveled, low organic matter, high pH calcareous soils

Corn, soybeans, grain and forage sorghums

Iron (Fe) Calcareous, exposed subsoils, low organic matter soils in western half of Kansas

Grain and forage sorghums, soybeans, field beans,

sudangrass,

Chlorine (Cl) Well drained soils in central and eastern Kansas with no history of potassium applications Wheat, grain sorghum, corn

Boron (B) Alkaline, well leached soils in southeastern Kansas, dry soil conditions

Alfalfa, sugar beets, soybeans, corns

Molybdenum (Mo) Soil pH less than 5.5, deficiencies very rare Alfalfa, legumes

Copper (Cu) Deficiencies not observed in Kansas - - - -

Manganese (Mn) Deficiencies not observed in Kansas - - - -

Nickel (Ni) Deficiencies not observed in Kansas - - - -

Zinc• Most frequently deficient micronutrient

• Absorbed by plant roots as Zn++

• Involved in the production of chlorophyll, protein, and several plant enzymes

• Deficiency symptoms• Most distinctive in corn with new leaves out of whorl

turning yellow to white in a band between the leaf midvein and margin

Zinc in the Soil

• Major soil reservoir of Zn is organic matter• Zn++ ion is adsorbed by CEC sites• Factors favoring Zn deficiency

– High pH, calcareous soils– Low organic matter– High phosphorus ?????????????– Sandy soils– Susceptible crops– Wet, cold soil conditions– Sugarbeet rotations

Phosphorus & Zinc

• Zn deficiency impairs plant P regulation.

• Large amounts of starter applied P can enhance Zn deficiency if soil Zn is low and no Zn fertilizer is applied.

P2O5 Zn Yield Leaf tissuelb/A * bu/A P, % Zn, ppm

0 0 101 0.14 120 10 102 0.16 2480 0 73 0.73 1080 10 162 0.41 17

Adriano and Murphy Kansas State University

* P and Zn band-applied

P and Zn Effects On Corn Yields

P2O5 Zn B’cast Starter

Lb / A Corn Yield (Bu/A)

0 0 107

0 10 121 115

40 0 121 93

40 10 139 140

St. Mary’s, KS – Kansas State University

P and Zn Effects On Corn YieldsP2O5 Zn B’cast Starter

Lb / A Corn Yield (Bu/A)

0 0 131

0 20 122 109

80 0 125 119

80 20 143 175

Belvue, KS – Kansas State University

Sources of Zinc

• Applied at relatively low rates (0.25-15 lb Zn/A)

• Zinc Sulfate– Good source for dry blends– Used to make fluid ammonia complex materials– The standard others are compared against

• Zinc OxideMuch less soluble than zinc sulfate. Must be finely divided to

be effective on neutral-acid soils. Do not use on high pH soils

• Zinc Oxysulfate• Made by acidulating zinc oxide with sulfuric acid• Generally made from industrial waste products• Most products work fine as zinc sources, a few may have low

water solubility. Minimum 50% water soluble. Prefer greater.

Sources of Zn Fertilizer

Zinc Source

InorganicZinc Sulfates

Zinc Oxide

Zinc Oxy-sulfate

Zinc Carbonate

Zinc-Ammonia Complexes

OrganicZinc Chelates

Other Organics

Zn (%)

22-36

77-80

20-36

52

10-20

9-14

5-10-20

Zinc Ammonia Complexes

• 10-0-0-10 Zn produced by ammoniating Zinc Sulfate or Zinc Chloride and diluting in water.

• Much more compatible in fluid fertilizers than zinc sulfate or oxide

• The fluid source to be used.

Chelates• Organic compounds that form a claw-like ring around metal

ions such as Zn++ that protects the zinc from soil fixation

• Chelates are more compatible than inorganic Zn sources in orthophosphate fluid solutions

• Chelates are more effective than inorganic sources under certain conditions

– 3 to 5 times more efficient?? on high pH soils unless banded with a polyphosphate where all Zn sources perform similarly

– Rates can be cut by 3/4 to 1/2 with chelated materials??

– The residual or carryover effect of a given rate of Zn as chelate is no better than an inorganic source

– Major disadvantage is the cost generally being 10 times the costof inorganic sources

Product Water

Solubility

Zn Application

Rate Ford Dodge Colby Ness Average(%) (Lb/A) (Change in DTPA Zn Soil Test - ppm)

0 0 -0.2 0.3 0.1 0.2 0.115 5 0.3 1.6 0.3 0.4 0.715 15 0.8 1.3 1.6 1.8 1.450 5 0.2 1.0 0.4 0.7 0.650 15 1.9 2.8 2.3 2.1 2.396 5 1.8 1.4 0.7 1.0 1.296 15 2.4 3.8 2.8 3.1 3.0

Effect Of Zinc Fertilizer Water Solubility On Long-Term Zinc Soil Test Values (DTPA)

Applied February 2003 - Sampled Spring/Summer 2004

Compost 5 0.0 0.7

Four Location Average% Water

Zn Source Soluble Zn Rate 2004 2005Check --- 0 0.0 0.0

Oxysulfate 15 5 0.4 0.2Oxysulfate 15 15 1.3 1.4Oxysulfate 50 5 0.7 0.6Oxysulfate 50 15 2.2 2.0Zinc Sulfate 96 5 1.1 0.8Zinc Sulfate 96 15 3.2 2.5

Probability > f < 0.01 < 0.01LSD (0.05) 0.8 0.6

Effect Of Zinc Fertilizer Water Solubility On DTPA Zn Soil Tests

Change In DTPA Soil Test Zinc (ppm)

Effect Of Zinc Fertilizer Water Solubility On DTPA Zn Soil Tests

% WaterSoluble Zn Rate Thomas Ness Dodge Ford Average

--- 0 0.0 0.0 0.0 0.0 0.015 5 0.2 0.2 0.4 0.3 0.315 15 1.9 1.5 1.0 1.0 1.450 5 0.7 0.5 0.9 0.4 0.650 15 2.5 2.1 2.0 1.7 2.196 5 0.9 0.8 0.9 1.4 1.096 15 3.7 2.9 2.9 2.0 2.9Probability > f < 0.01 < 0.01 < 0.01 < 0.01 < 0.01

LSD (0.05) 0.5 0.5 0.8 * 0.9 * 0.5

Soil Test Zinc (ppm)Change In DTPA

Effect Of Various Zinc Sources On DTPA Zn Soil Test

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 2 4 6 8 10 12 14 16Total Zn Application Rate (lb Zn/A)

Chan

ge In

DTP

A Zn

Soi

l Tes

t (pp

m)

Measured - 15% Water Solubility Measured - 50% Water Solubility Measured - 96% Water Solubility

0.1984 ppm DTPA Zn Change per Pound Of Water Soluble Zn0.0686 ppm DTPA Zn Change per Pound Of Water Insoluble Zn

R2 = 0.96

Soluble Zn ~ 5 lbs Zn per 1 ppm DTPA ZnInsoluble Zn ~ 15 lbs Zn per 1 ppm DTPA ZN

Application Methods

• Broadcast– Preferred to correct a low Zn soil test– 5 to 15 pound will increase soil test for a number of years– Inorganic Zn is more economical than chelates at these

rates

• Band– Very efficient method of applying Z– 0.5 lb Zn/Acre of inorganic Zn is generally sufficient– Annual applications will be needed for low testing soils– All sources are equally effective when applied with

fertilizer materials high in polyphosphates• Zn should be limited to 1 lb per 22 lbs P2O5 from 10-34-0• If longer shelf life required, only use 1/2 lb

Chloride (Cl)• Essential nutrient – wheat, corn sorghum

deficiencies in Kansas

• Deficiencies most likely in higher rainfall areas with no K application history - central and eastern part of state

• Soluble, mobile anion

• Addition of KCl– Increased yields with high levels of available K– Reduced incidence of plant disease– Internal water relationships, osmotic regulation, enzyme

activation and other plant processes

Chloride fertilization on corn in Kansas.Grain Yield

Chloride Riley Co. Brown Co. Osage Co.

Rate Site A

Site B

Site C Site A Site B

Site C

Site A

Site B

lb/a - - - - - - - - - - - - - - - - - - bu/a - - - - - - - - -- - - - - - - - -

0 70 64 107 188 123 87 133 79

20 84 69 111 191 130 93 133 81

Soil test Cl, lb/a (0-24")

9 16 24 28 14 28 40 61

Chloride fertilization on wheat.Grain Yield*

Chloride Marion Co. Saline Co Stafford Co.

Rate Site A Site B Site A

Site B Site C Site D Site A

Site B Avg.

lb/a - - - - - - - - - - - - - - - - - - - - - - - bu/a - - - - - - - - - - - - - - - - - - - - -

0 45 80 51 89 83 70 73 64 69

20 47 85 54 89 90 75 80 70 74

Soil test Cl, lb/a (0-24")

7 7 14 22 7 14 7 15 12

*Average over either 12 or 16 varieties. Soil test Cl, lb/a (0-24")

Chloride fertilization on grain sorghum in Kansas

Grain Yield

Chloride Marion Co. Brown Co. Osage Co.

Rate Site A Site B Site C Site D Site A Site B Site A Site B

lb/a- - - - - - - - - - - - - - - - - - bu/a - - - - - - - - - - - -

- - - - - -

0 87 117 63 92 102 87 125 88

10 94 139 71 113 106 95 126 92

20 97 135 72 126 111 96 125 96Soil test Cl, lb/a (0-24")

9 7 9 43 7 9 52 29

Approximate Chloride Content of Some Common Fertilizers

Fertilizer

0-0-60

5-20-35

6-24-24

8-32-16

13-13-13

Calcium chloride

Ammonium chloride (dry)

Amm. Chloride (solution)

Cl %

45-46

26

18

12

9.7

65

66

16.5

Iron (Fe)

• Iron in the plant– Catalyst in the production of chlorophyll– Involved with several enzyme systems

• Deficiency symptoms– Yellow to white leaf color– Symptoms first appear on the younger leaves– Wide range of susceptibility of different crops

• Sorghum, field beans and soybeans are more sensitive than corn and alfalfa

• Varieties differ within crops• Cultivation can reduce iron chlorosis by aerating, warming

and drying the soil

Factors Affecting Iron Availability– High soil pH– Cool, wet springs– Poor soil drainage and aeration– Susceptible crops/varieties

• Soil tests and plant analysis– Kansas has Fe soil test, but …………..– Plant analysis is not a consistent indicator

Fertilizer Sources of Iron• Deficiencies occur more frequently than most other

micronutrients in Kansas

• Patchy or irregular appearance in the field

• Success with iron fertilization is difficult– Difficulty in correcting Fe deficiency with soil-applied

fertilizer

• Iron quickly converted to unavailable form.• Certain Fe chelate carriers (EDDHA) have been effective but

have not been economical and may require multiple applications• Foliar Application most promising

Foliar Applications

• Applications must be done before plants are severely damaged by chlorosis and may need to be repeated

• Ferrous sulfate (1-2% solution) plus a wetting agent or one of several iron chelates/complexes may be used

• Critical timing– Soybean - by the first trifoliate leaf– Sorghum - apply by the 6th leaf stage

Common Iron Fertilizers

Fertilizer Source

Iron Sulfate

Iron Chelates

Other Organics

Manure - best

Fe (%)

19-40

5-12

5-11

??

The rating scale:

1 = no chlorosis, plants normal and green2 = slight yellowing, no differentiation between veinal and interveinal areas on the leaf3 = interveinal chlorosis (leaf veins green but interveinal areas yellow), but no indication of stunting of growth or necrosis (death) of leaf tissue4 = interveinal chlorosis with reduced growth or some necrosis of leaf tissue5 = very severe chlorosis, plants with stunted growth, and youngest leaves and growing point necrotic, or entire plants dead.

North Dakota State University Soybean Iron ChlorosisJay Goos

Boron• Essential for germination of pollen tubes and grains

• Immobile nutrient within plants so first expressed in the new growth

• Most commonly affected plants include sugar beets, alfalfa, clover, celery, beets cauliflower, apples, grapes pears, walnutsand ornamentals

• Boron exists as borate anion and is mobile

• Soils and conditions where deficiencies are most likely to exist– Highly leached sandy soils– Low organic matter soils– Dry soil Conditions

• Soil tests are not well calibrated in Kansas

Effects of Lime, P, K and Boron On Crop Yield. Cherokee County, KS, 1963-1972

Crop Yields

Crop Alfalfa Corn Wheat SoybeanTon/A - - - - Bu/A - - - -

Control 0.72 43 21 22Lime 1.08 43 27 25

Lime P 2.95 54 38 28Lime P, K 3.28 67 43 30

Lime, P, K, B 3.72 73 44 34

Fertilizer Sources of Boron

• Narrow range between deficiency and toxicity• Application guidelines

Use low rates1lb B/A/yr for alfalfa should correct problemNever place in contact with seedBe careful of segregation problems when applying B in blends of P and K With low rates, uniform distribution is importantLiquid sources minimizes segregation issues

Common Boron Fertilizer Sources

Fertilizer Source

Borax

Boric Acid

Solubor

B (%)

11

17

20-20.5

Copper (Cu)• Involved in chlorophyll formation and catalyst for several plant

processes

• Deficiency symptoms are rare (not found in Kansas)

• Small grains and vegetables are most sensitive crops

• Held tightly by organic matter so deficiencies are most likely to occur in peat and muck soils

• No correlated soil test in Kansas

• Copper application guidelines– Copper has a long residual life in the soil– Over application can be toxic to plants– Copper is also applied as a fungicide on some crops.

Manganese (Mn)• Recent potential responses noted in Kansas

• Enzymatic reactions and is involved in the synthesis of chlorophyll

• Immobile in plants

• Most frequently deficient in organic soils or alkaline mineral soils with low CEC

• In poorly drained highly acidic soils, Mn toxicity rather than deficiency is more likely to occur

• Soil tests for Mn are not well calibrated

• Wheat, barley and corn symptoms occur on the upper leaves developing yellow streaks running the length of the leaf

• Soybeans, snap beans, oats and vegetables are most likely crops to show deficiency symptoms

Function of Manganese

Important in photosynthesis (splitting of water molecule and evolution of oxygen).Activates enzymes leading to the biosynthesis of lignin and flavonoids. Flavonoids in legumes stimulate nodulation gene expression.Responsible for degradation of fixed N transported from roots to shoots.

Manganese Nutrition of Glyphosate–Resistant and Conventional Soybeans

B. Gordon and S. Duncan

Kansas State University

Manganese Deficiency

Manganese Deficiency

Mn nutrition problems with herbicide resistant soybeans

Insertion of gene giving herbicide resistance changed soybean root exudates. Plants solublize less Mn than conventional soybeans.Glyphosate application may interfere with Mn metabolism within the plant.

Mn Effects on Soybean Yield, 2004

50

55

60

65

70

0 2.5 5 7.5

Mn-Rate, lb/a

Yiel

d, b

u/a

MaconAsgrow 3302

Mn Application Effects on Soybean Yield, 2005

55606570758085

0 2.5 5 7.5

Mn-Rate, lb/a

Yiel

d, b

u/a

KS 4202KS4202 RR

Mn Application Effects on Leaf Tissue Mn Concentration, 2005

0

20

40

60

80

100

0 2.5 5 7.5

Mn-Rate, lb/a

Leaf

Tis

sue

MN

, ppm

KS 4202KS 4202 RR

Molybdenum (Mo)• No deficiencies in Kansas

• Conversion of nitrates to ammonium within the plant

• Essential to N fixation by legume nodules

• Required in smaller amounts than other essential plant nutrients

• Molybdenum in Soil– 2 to 20 pounds total in the soil– anion as molybdate (MoO4

-)– Only nutrient whose availability increases with soil pH– Deficiencies most frequently occur in legume crops on very acid,

sandy soils

Nickel (Ni)• No deficiencies in Kansas

• Just recently identified as essential nutrient

Micronutrient Management

• Zinc Zn• Iron Fe• Boron B• Copper Cu• Manganese Mn• Molybdenum Mo• Chlorine Cl• Nickel