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II. Status in World Soils

II. Status in World Soils

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189



MICRONUTRIENTS IN CROP PRODUCTION



grown in various parts of the world (Cakmak, Sari et al., 1996; Fageria, 2000a;

Galr˜ao, 1999; Graham et al., 1992; Grewal and Graham, 1999; Mandal and Mandal,

1990; Martens and Lindsay, 1990). It has been estimated that 3.95 billion ha of

the world’s ice-free land area is subject to mineral stresses for plants, with 14%

of this area being subject to potential micronutrient stresses (Gettier et al., 1985).

The reasons for micronutrient deficiencies are that these elements have not usually been applied regularly to soils through fertilization. Furthermore, increased

crop yields, loss of micronutrients through leaching, liming of soils, decreased

use of manures compared to chemical fertilizers, and increased purity of chemical

fertilizers without micronutrient additions have contributed to accelerated exhaustion of available micronutrients in soils. Hidden micronutrient deficiencies may

be more widespread than has generally been suspected. Potential micronutrient

deficiencies/toxicities associated with major soil groups (Table I), common soil



Table I

Potential Micronutrient Deficiencies or Toxicities Associated with Major Soil Groupsa

Element problem

Soil order

Andosols (Andepts)

Ultisols

Ultilsols/Alfisols

Spodosols (Podsols)

Oxisols

Histosols

Entisols (Psamments)

Entisols (Fluvents)

Mollisols (Aqu), Inceptisols,

Entisols, etc. (poorly drained)

Mollisols (Borolls)

Mollisols (Ustolls)

Mollisols (Aridis) (Udolls)

Mollisols (Rendolls) (shallow)

Vertisols

Aridisols

Alfisols/arid Entisols

Alfisols/Utisols (Albic)

(poorly drained)

Alfisols/Aridisols/Mollisols

(Natric) (high alkali)

Aridisols (high salt)



Soil group



Deficiency



Andosol

Acrisol

Nitosol

Podsol

Ferralsol

Histosol

Arensol

Fluvisol



B, Mo

Most micronutrients



Gleysol

Chernozem

Kastanozem

Phaeozem

Rendzina

Vertisol

Xerosol

Yermosol



Mn

Fe, Mn, Zn

Cu, Mn, Zn

Fe, Mn, Zn

Fe

Fe, Zn

Co, Fe, Zn



Planosol



Most micronutrients



Solenetz

Solonchak



Cu, Fe, Mn, Zn



Most micronutrients

Mo

Cu

Cu, Fe, Mn, Zn



Toxicity



Fe, Mn

Mn

Fe, Mn



Fe, Mn

Fe, Mo



Mo



B, Cl



a

Modified from Baligar and Fageria (1999); Clark (1982); Dudal (1976); S. W. Buol, North

Carolina State University, Raleigh; H. Eswaren, USDA-NRCS, Washington, DC.



190



FAGERIA et al.

Table II

Major Soil Minerals Containing Micronutrientsa



Element

B



Cl



Cu



Fe



Mn



Mo



Zn



Ni



Co



a



Type

Borates (hydrous)

Borates (anhydrous)

Complex borosilicates

Sylvite

Kainite

Langbeinite

Carbonates

Oxides

Simple sulfides

Complex sulfides

Carbonates

Oxides

Sulfides

Sulfates

Carbonates

Simple oxides

Complex oxides

Silicates

Oxides

Molybdates

Sulfides

Carbonates

Sulfides

Silicates

Pentlandite

Awaruite

Cohenite

Haxonite

Nickel

Cobaltite

Skutterudite

Erythrite



Mineral

Borax—Na2B4O7·10H2O; Kernite—Na2B4O7·4H2O;

Colemanite—Ca2B6O11·5H2O; Ulexite—NaCaB5O9·4H2O

Ludwigite—Mg2FeBO5; Kotoite—Mg3(BO3)2

Tourmaline; Axinite

KCl

KCl; MgSO4·3H2O

K2SO4·2MgSO4

Malachite—Cu2(OH)2CO3; Azurite—Cu3(OH)2(CO3)2

Cuprite—Cu2O; Tenorite—CuO

Chalcocite—Cu2S; Covellite—CuS

Chalcopyrite—CuFeS2; Bornite—Cu3FeS4; Digenite—Cu9S5;

Enargite—Cu3AsS4; Tetrjedrote—Cu12Sb4S13

Siderite—FeCO3

Hematite—Fe2O3; Goethite—FeOOH; Magnetite—Fe3O4

Pyrite—FeS2; Pyrrhotite—Fe1–xS

Jarosite—KFe3(OH)6(SO4)4

Rhodochrosite—MnCO3

Pyrolusite—MnO2; Hausmannite—Mn3O4;

Manganite—MnOOH

Braunite—(Mn, Si)2O3; Psilomelane—BaMg9O18·2H2O

Rhodanate—MnSiO3

Ilsemanite—Mo3O8·8H2O

Wulflenite—PbMoO4; Powellite—CaMoO4;

Ferrimolybdite—Fe2(MoO4)·8H2O

Molybdenite—MoS2

Smithsonite—ZnCO3

Sphalerite—ZnS

Hemimorphite—Zn4(OH)2Si2O7·H2O

(Fe, Ni)9S8

Ni3Fe

(Fe,Ni)3C

(Fe,Ni)23C6

Ni

CoAsS

CoAs2–3

Co3(AsO4)·8H2O



From Chesworth (1991), Dana and Dana (1997), Krauskopf (1972), and Mortvedt (2000)



minerals containing various micronutrient elements (Table II), and concentration

ranges of micronutrients in soils and plants (Table III) have been provided to help

define where micronutrient problems might occur.

Concentrations of B in soils range from about 2 to 100 mg kg−1 (mean of

10 mg kg−1) and generally occurs as H3BO3/B(OH)3 (Goldberg, 1993). Soils



Table III

Essential Micronutrients for Plant Growth, Principal Forms Absorbed, Concentration Ranges in Plants and Soils, and Persons Demonstrating

Essentiality in Plants

Concentration range

in plantsa (mg kg−1)



Concentration

in soilb,c (mg kg−1)



Element



Form absorbed



Critical



Sufficient



Toxic



B

Cl

Cu



H3BO3; BO3−; B4O72−

Cl−

Cu2+



<10

<2000

3–5



10–100

2000–20000

5–20



50–200

>20000

20–100



Fe

Mn

Mo

Zn

Ni

Co



Fe2+; Fe3+

Mn2+

MoO42−

Zn2+

Ni2+

Co2+



<50

10–20

<0.1

15–20

1.0–5

<0.2



50–250

20–300

0.1–0.5

20–100

0.1–5

0.2–0.5



>1000

300–500

10–50

100–400

10–100

15–50



a



Bennett (1993) and McBride (1995).

Alloway (1995a) (critical level above which toxicity is likely).

c

Kabata-Pendias and Pendias (1992).

d

Marschner (1995).

b



Normal

2–150

20–900

2–250

200–500,000

7–10,000

0.1–40

1–900

0.4–1000

0.1–70



Critical total



Demonstration of essentialityd



15–25

70–200

60–125



K. Warington(1923)

T. C. Broyer et al. (1954)

A. L. Sommers, C. B. Lipman, and

G. MacKinney (1931)

J. Sachs (1860) Knop.

J. S. McHargue (1922)

D. I. Arnon and P. R. Stout (1939)

A. L. Sommers and C. B. Lipman (1926)

P. H. Brown et al. (1987)



1000–3000

2–13

70–400

100

25–50



192



FAGERIA et al.



formed from igneous rock contain less B than soils formed from marine sediments. Soils derived from granite, igneous, and acidic rocks and metamorphic

sediments are often poor in B (Gupta, 1979). Low B soils are usually strongly

weathered (Acrisols, Podzols, Ferralsols), coarse textured (Arenosols), and shallow (Lithosols) (Shorrocks, 1997). In acidic rocks and metamorphic sediments,

B occurs in tourmaline minerals and is not readily available to plants. Boron adsorption usually increases with increasing soil solution pH, temperature, ionic

strength, and nature of adsorbed cations (Goldberg, 1993, 1997). The amount of B

adsorbed in fine-textured soils usually increases with enhanced clay contents. For

example, montmorillonitic clays normally adsorb greater amounts of B than illitic

clays (Goldberg and Glaubig, 1986). Competitive anion effects on B adsorption

increased in the order of P > Mo > S even though the competitive effect was low,

indicating that B adsorption sites are generally specific for B (Goldberg, 1997;

Goldberg, Forster, and Lesch et al., 1996). The B-adsorbing surfaces in soils are

commonly Al and Fe oxides, Mg hydroxides, clay minerals, Ca carbonates, and

organic matter (OM). The distribution of B between soil solution and adsorption

surfaces is affected by clay mineral types, content, and specific surface areas, mineralogy of sand/silt fractions, sesquioxides, SOM content, pH, ions on exchange

sites, and salinity (Elrashidi and O’Conner, 1982; Evans and Sparks, 1983; Gupta

et al., 1985). These soil factors also affect the retention of B in soils (Gupta, 1993).

The availability of B is commonly reduced in soils high in Al oxides (Bingham

et al., 1971) as well as in volcanic ash soils (Sillanpăaaă and Vlek, 1985). In soil, B is

normally present as nonionized molecules and easily lost by leaching. In arid and

semiarid regions particularly, B toxicity can be of major concern (Gupta, 1979).

Chlorine is ubiquitous in soils and occurs in aqueous solutions such as Cl−. Soil

Cl is not tightly held by soil-exchange sites and is readily leached. Chlorine is

commonly added to soil with manures and fertilizers(KCl), rainfall, sea spray, and

irrigation waters (Needham, 1983).

Copper is mostly found in silt and clay fractions of soil and usually present

in carbonate fractions in alkaline soils and in Fe oxide fractions in acid soils

(Shuman, 1991). Concentrations of Cu in soils range from about 2 to 100 mg kg−1

(mean of 30 mg kg−1) (Mortvedt, 2000). Crops grown in soils developed from

sand, sandstones, acid igneous rocks, and calcareous materials often exhibit Cu

deficiency, but deficiencies are not generally found on plants grown in clays and

in soils formed from basic rocks (Jarvis, 1981a). In the United States, soils formed

from weathered bed rocks have high Cu, whereas soils formed in the lower Atlantic

coastal plains have low Cu (Kubota, 1983). Organic, peat, and muck soils generally

have low amounts of labile Cu (Oplinger and Ohlrogge, 1974). When histosols

are brought under cultivation, plants commonly exhibit Cu deficiency, which has

been termed as a “reclamation disease” (Welch et al., 1991).

Iron is the most abundant of the micronutrients in the lithosphere (Mortvedt,

2000). Soil concentrations of Fe range from 7000 to 500,000 mg kg−1 (mean of



MICRONUTRIENTS IN CROP PRODUCTION



193



38,000 mg kg−1 or 3.8% in soil) (Lindsay, 1979). Most Fe in the Earth’s crust is in

the form of ferromagnesium silicate. Iron is precipitated as Fe oxides or hydroxides

during weathering, and small fractions of Fe are incorporated into secondary silicate materials (Schwertmann and Taylor, 1977). Iron deficiency occurs commonly

on plants grown in calcareous and noncalcareous coarse-textured soils, especially

in arid/semiarid regions. However, Fe deficiency can also occur on plants grown in

acid soils. About 4.8 million ha of land west of the Mississippi river in the United

States (intermountain region) is prone to Fe deficiency in “Fe-inefficient” crops

(Mortvedt, 1975). Alkaline, calcareous, and acidic sandy soils in Florida have also

been prone to Fe deficiency on citrus (Welch et al., 1991). Iron deficiency has also

been closely related to Ca carbonate equivalency and soluble salts in soil (Franzen

and Richardson, 2000). High soil pH, SOM, CaCO3, HCO3−, and Ca contents have

also been related to decreased Fe acquisition in some plants (Kăoseoglu, 1995). Iron

deciency also occurs in various regions of Europe, east India, Bangladesh, and

in most Mediterranean and west African countries (Welch et al., 1991). Low Fe

soils and Fe-deficient crops have been reported for certain areas of Malta, Turkey,

Zambia, and Mexico (Sillanpăaaă , 1982), Indonesia (Katyal and Vlek, 1985), several

Central and South American countries (Leon et al., 1985), and in south Australia,

Victoria, and western Australia (Donald and Prescott, 1975). Excess Fe (toxicity)

has been reported on rice grown under flooded conditions in acid soils of China,

Vietnam, Thailand, Burma, Bangladesh, Sri Lanka, Malaysia, Phillippines, and

Indonesia (Vose, 1982). Kang and Osiname(1985) also reported Fe toxicity on

plants grown in the acid soil belt of equatorial Africa, which includes Senegal,

Gambia, Liberia, and Sierra Leone.

Manganese is the 10th most abundant element in the Earth’s crust. Soil Mn

concentrations range from about 20 to 3000 mg kg−1 (mean of 600 mg kg−1)

(Lindsay, 1979). Soil Mn appears in primary and secondary minerals, is sorbed onto

mineral and OM surfaces, and incorporated into soil organisms and in soil solution.

Soils derived from crystalline shales and acid igneous rocks have low reducible

Mn, and soils derived from basalt, limestone, and shale commonly have high Mn

(Glinski and Thai, 1971). High extractable Mn has been reported for Inceptisols

and Vertisols and low extractable Mn has been reported for Ultisols and Oxisols

(Lombin, 1983). Labanouskas (1966) and Reuter et al. (1988) grouped the world

soils with less than adequate levels of available Mn as (i) shallow, peaty, marsh, and

alluvial soils developed from calcareous parent materials; (ii) calcareous soils with

poor drainage and high OM, calcareous black sands, and calcareous grassland soils

recently brought into cultivation; (iii) soils occurring over limed and reclaimed acid

heath soils; and (iv) sandy acid soils containing low native Mn.

Manganese deficiency has been reported for plants grown in coarse-textured and

poorly drained coastal plains soils of the United States (Reuter et al., 1988) and in

soils of Central America, Bolivia, and Brazil (Leon et al., 1985). In Europe, Mn

deficiency has been reported for plants grown in peaty (England and Denmark),



194



FAGERIA et al.



coarse-textured (Sweden and Denmark), coarse/fine-textured (Netherlands), and

podzolic and brown forest (Scotland) soils (Welch et al., 1991). Manganese deficiency has also been reported on plants grown in semiarid regions of China, India,

southeast and western Australia, Congo, Ivory Coast, Nigeria, and other western

African countries. Manganese toxicity on crop plants grown in many parts of the

world has been reported to be more important than Mn deficiency (Foy, 1984;

Welch et al., 1991).

Molybdenum is the least abundant of the micronutrients in the lithosphere

(Mortvedt, 2000), and soil concentrations range from about 0.2 to 5 mg kg−1

(mean of 2 mg kg−1). Plants exhibiting Mo deficiency usually occur on plants

grown in broad areas of acid well-drained soils and in soils formed from parent

materials low in Mo. In Australia, Mo deficiency occurred on crops grown in soils

derived from sedimentary rocks, basalts, and granites (Anderson, 1970). Peaty,

alkaline, and poorly drained soils commonly have high Mo. Iron oxides adsorb

more Mo than Al oxides (Jones, 1957), and Mo adsorption on clays followed the

sequence of montmorillonite > illite > kaolinite (Goldberg, Forster et al., 1996).

Hydrous ferric oxides or ferric oxide molybdate complexes and insoluble ferric

molybdates may form in well-aerated soils so that Mo solubility and availability to

plants are low (Welch et al., 1991). In poorly drained soils, formation of soluble ferrous molybdates or molybdites may lead to high Mo availability to plants. Plants

grown in high Mo soils of the intermountain valleys of western United States

have been reported to accumulate high Mo which has induced “molybdenosis”

(Cu deficiency) in cattle (Welch et al., 1991).

Zinc deficiency is a worldwide nutritional constraint for crop production. About

50% of soils used for cereal production in the world contain low levels of plantavailable Zn, which reduces not only grain yield but also nutritional grain quality

(Graham and Welch, 1996). Total Zn concentrations in soils range from about

10 to 300 mg kg−1 (mean of 50 mg kg−1)(Lindsay, 1979). Zinc-deficient soils

occur in both tropical and temperate regions, but are widespread in Mediterranean

countries like Turkey (Cakmak et al., 1997), and in New South Wales, Queensland,

and western and south Australia (Donald and Prescott, 1975; Sillanpăaaă and Vlek,

1985). In China, Zn deficiency has been reported on plants grown in calcareous,

desert, and paddy soils along the Yangtze river (Takkar and Walker, 1993). In

Africa, Zn deficiency has been observed on plants grown in Alfisols and Ultisols

(Cottenie et al., 1981) and in low Zn soils of Niger, Guinea, Ivory Coast, Sierra

Leone, Sudan, and Zimbabwe, which has often been induced by lime additions to

increase soil pH to near 7. In Asia, Zn deficiency is common for plants grown in arid

and semiarid soils (Katyal and Vlek, 1985; Welch et al., 1991). Zinc deficiency in

the United States has occurred mostly in plants grown in sandy, well-drained acid

soils, and in soils formed from phosphate rock parent materials of the southeast.

In the Cerrado soils of Brazil (Oxisols and Ultisols), Zn deficiency is widespread

(Fageria, 2000b; Lopes and Cox, 1977).



MICRONUTRIENTS IN CROP PRODUCTION



195



Serpentine (ultramafic) soils are usually high in Ni, Co, Fe, and Mg, but low in

Ca. Nickel levels in soils are usually adequate to provide plant needs. No evidence

of Ni deficiency for soil-grown plants has been reported (Dalton et al., 1985),

but Ni toxicity has been of concern for plants grown in soils receiving industrial

wastes (sewage sludges, by-products) (Marschner, 1995). Cobalt deficiency has

been reported for ruminant animals grazing forages grown in soils low in Co such

as New Zealand, south and western Australia, The Netherlands, and the United

States (Michigan and northeastern states) (Miller et al., 1991). Cobalt is adsorbed

on Mn oxides, and liming tends to reduce Co availability to plants.



III. SOIL FACTORS AFFECTING AVAILABILITY

Many soil factors such as pH, SOM, temperature, and moisture affect the availability of micronutrients to crop plants. The effects of these factors vary considerably from one micronutrient to another as well as in their relative degree of

effectiveness. The availability of micronutrients is largely controlled by the same

soil factor(s) where good correlations exist between plant concentrations of two

or more micronutrients. The relationships associated with each of the many soil

factors are complicated, even though correlations between many factors can be

explained with relatively high certainty. A good example of this is the highly significant negative correlation between Mo and Mn. The availability of both Mo and

Mn is so strongly affected by soil pH that the other factors are of limited value.

While Mn in plants decreases extensively with increasing soil pH, Mo increases,

and deficiencies of both Mn and Mo are not expected or do not usually occur in the

same soil. Manganese deficiency is often combined with excess Mo and vice versa

(Sillanpăaaă , 1982). Copper, Mn, and Zn were predominantly in organically bound

forms in Spodosols of Florida, whereas these elements were organically bound

and associated with Mn oxides and amorphous forms in Alfisols and Entisols

(Zhang et al., 1997a). Available concentrations of Co, Cu, Ni, and Zn increased

with increased amounts of clay (Lee et al., 1997).



A. pH

Soil pH influences solubility, concentration in soil solution, ionic form, and mobility of micronutrients in soil, and consequently acquisition of these elements by

plants (Fageria, Baligar and Edwards, 1990; Fageria, Baligar, and Jones, 1997). As

a rule, the availability of B, Cu, Fe, Mn, and Zn usually decreases, and Mo increases

as soil pH increases. These nutrients are usually adsorbed onto sesquioxide soil

surfaces. Table IV summarizes important changes in micronutrient concentrations



196



FAGERIA et al.

Table IV

Influence of Soil pH on Micronutrient Concentrations in Soil and Plant Uptakea



Element

B

Cl



Influence on concentration/uptake

Increasing soil pH favors adsorption of B. This element generally becomes less available

to plants. Availability and uptake of B decrease dramatically at pH > 6.0.

Chloride is bound tightly by most soils in mildly acid to neutral pH soils and becomes

negligible to pH 7.0. Appreciable amounts can be adsorbed with increasing soil acidity,

particularly by Oxisols and Ultisols, which are dominated by kaolinitic clay. Increasing

soil pH generally increases Cl uptake by plants.



Cu



Solubility of Cu2+ is very soil pH dependent and decreases 100-fold for each unit

increase in pH. Plant uptake also decreases.



Fe



Ferric (Fe3+) and ferrous (Fe2+) activities in soil solution decrease 1000-fold and

100-fold, respectively, for each unit increase in soil pH. In most oxidized soils, uptake

of Fe by crop plants decreases with increasing soil pH.



Mn



The principal ionic Mn species in soil solution is Mn2+, and concentrations decrease

100-fold for each unit increase in soil pH. In extremely acid soils, Mn2+ solubility can

be sufficiently high to induce toxicity problems in sensitive crop species.



Mo



Above soil pH 4.2, MoO42− is dominant. Concentration of this species increases with

increasing soil pH and plant uptake also increases. Water-soluble Mo increases sixfold

as pH increases from 4.7 to 7.5. Replacement of adsorbed Mo by OH− is responsible

for increases in water-soluble Mo as soil pH increases.

Zinc solubility is highly soil pH dependent and decreases 100-fold for each unit increase

in pH, and uptake by plants decreases as a consequence.



Zn

Ni



Co



a



Ni2+ is relatively stable over wide ranges of soil pH and redox conditions. However,

availability is usually higher in acidic than in alkaline soils. At pH 7 and higher,

retention and precipitation increase. Increasing the pH of serpentine soils through

liming from 4 to 7 reduced Ni in plant tissue.

Solubility and availability of Co decrease with extreme soil pH. Presence of CaCO3, and

high Fe, Mn, SOM, and moisture.



Adriano (1986), Fageria, Baligar, and Jones (1997), and Tisdale et al. (1985).



as influenced by soil pH and consequent acquisition by plants. Table V has been

provided to show acquisition of Cu, Fe, Mn, and Zn by rice grown at various soil

pH values.

Boron is the only micronutrient to exist in solution as a nonionized molecule

over soil pH ranges suitable for the growth of most plants. Increasing soil pH decreases B availability by increasing B adsorption onto clay and Al and Fe hydroxyl

surfaces, especially at high soil pH (Keren and Bingham, 1985). The highest availability of B was at pH 5.5–7.5, and the availability decreased below or above this

pH range. In other studies, B adsorption increased from pH 3 to 8 on kaolinite,



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