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Influence of inducedsalinity and sodicity onmanganese sorption invertisols and aridisolsE.A. El‐Amin a b , A.A. Hussein a & Y.E. El Mahia

a Department of Soil Science, Facultyof Agriculture‐Shambat , University ofKhartoum , Sudanb P.O. Box 439, PC 111, Muscat, Sultanate ofOman E-mail:Published online: 11 Nov 2008.

To cite this article: E.A. El‐Amin , A.A. Hussein & Y.E. El Mahi (2000) Influenceof induced salinity and sodicity on manganese sorption in vertisols and aridisols,Communications in Soil Science and Plant Analysis, 31:3-4, 455-463, DOI:10.1080/00103620009370449

To link to this article: http://dx.doi.org/10.1080/00103620009370449

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COMMUN. SOIL SCI. PLANT ANAL., 31(3&4), 455-463 (2000)

Influence of Induced Salinity and Sodicityon Manganese Sorption in Vertisols andAridisols

E. A. El-Amin,1 A. A. Hussein, and Y. E. El Mahi

Department of Soil Science, Faculty of Agriculture-Shambat, University ofKhartoum, Sudan

ABSTRACT

Salinity and sodicity effects on manganese (Mn) sorption in a mixed sodium-calcium (Na-Ca) soil system were studied. Soil samples were taken at 0-30cm depth from Vertisols (El-Hosh and El-Suleimi) and Aridisols (El-Laota)at three sites in Gezira scheme (Sudan). No Mn was applied to these soils.Prior to analysis the soils were equilibrated with NaCl-CaCL2 mixed saltsolutions to attain SAR values at different salt concentrations. The resultsindicated that saline soils sorbed less Mn and had higher equilibrium Mnconcentrations. Sodic soils retained more Mn but had low equilibriumconcentrations. Sodicity had a pronounced effect only on increasing Mnretention at higher SAR values. Salinity tended to alleviate sodicity effectson Mn retention, but soluble salts that increased soil pH decreased Mnconcentration.

1 Corresponding author (present address: P.O. Box 439, PC 111, Muscat, Sultanate of Oman;e-mail address: Elamin2@hotmail.com).

455

Copyright © 2000 by Marcel Dekker, Inc. www.dekker.com

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456 EL-AMIN, HUSSEIN, AND EL MAHI

INTRODUCTION

The Mn concentration in soil solution was found to increase with increasingelectrolyte concentration (C) (Page, 1974; Pasricha and Pennamperuma, 1976;Khattak and Jarrell, 1988). In an isoequivalent NaCl-CaCl2 mixture, those authorsreported that increasing (C) increased soluble Mn in a variety of California soilsincubated at the paste saturation moisture content. If electrolyte concentrationaffected native Mn desorption, it is conceivable that it may also affect sorption bysoils.

Little work, if any, has been reported on the effect of sodicity on Mn adsorption,despite the fact that many sodic soils are characteristically deficient in Mn (Leeper,1949). Pasricha and Pennamperuma (1976) observed a decrease in Mnconcentration due to increasing NaHCO3 content, and associated that withincreasing pH rather than with sodicity because they found increasing NaCl contentincreased Mn concentration. On the other hand, Sadig (1981) found Mn sorptionin 27 arid-zone soils to be independent of pH and other soil properties. Therefore,in light of these conflicting views, the present experiment is conducted to studythe effects of salinity and sodicity on Mn retention by soils.

MATERIALS AND METHODS

Soil Materials

Samples were taken from the top (0-30 cm) layer of three soils from GeziraScheme, located between the Blue and White Niles, Sudan. The soils belong tothe Vertisols (El Hosh and El Suleimi series) and Aridisols (El Laota series). TheHosh series (H) is classified as a fine smectitic isohyperthermic Typic Pellustert,Suleimi series (S) as a fine smectitic isohyperthermic Entic Chromustert, and theLaota series (L) as a fine-loamy, mixed, isohyperthermic Typic Camborthid. Thesesoils had no previous history of Mn application, and some of their characteristicsare given in Table 1. Particle size analysis was carried out by the pipette method,organic carbon was determined by the Walkley-Black method, CEC by the sodiumacetate-ammonium acetate method and the soil suspension (soihwater = 1:5) pHby the glass electrode method (Page et al., 1982). Extractable iron oxide wasdetermined by the method of Hohngren (1967) and total Mn was determinedaccording to the method described by Chapman and Pratt (1961).

For each soil, five samples were prepared each having SAR values of 0, 5,15,25 and 50 [SAR = Na/(Ca/2)'/l, where all concentrations are expressed in mmolj.Specific SAR values were attained by shaking soil samples repeatedly inappropriate salt solutions and then washing excess salts by alcohol. Detaileddescription of sample preparation was given by El Mahi and Mustafa (1980).The treated samples were air dried and crushed to pass a 1-mm sieve.

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SALINITY AND SODICITY ON Mn IN VERTISOLS AND ARIDISOLS 457

TABLE 1. Selected physical and chemical properties of the soils used.

Properties

Particle size analysisClay <2 ixm (%)Silt 20-2 ^m(%)Sine sand 200-20 fim (%)Coarse sand 2-0.2 mm (%)

CaCO3 %Organic carbon %CECmmoL/lOOgExtractable iron oxides %Clav minerals <0.2 urn clav fraction(Adam et al., 1983)

Smectite %Mica%

Total MnO %MnO % in clay fraction

SoilsHosh

6025783.80.59

552.2

5570.160.05

Laota

391715295.80.34

361.4

5370.190.06

Suleimi

5825982.80.4

542.0

5570.180.07

Analytical Methods

Manganese adsorption studies were conducted with samples which werepreviously equilibrated with the specified SAR values. Three times 2.5 g of eachsoil sample were weighed in 50 mL polypropylene centrifuge tubes and shakenfor 2 hrs at 30°±2°C with 25 mL aliquots of salt solution containing one of thefollowing electrolyte concentrations: 200, 100, 40, 20, and 3 mmoL Thesesolutions contained graded concentrations of Mn: 1, 2, 3, 4, and 5 mg Mn L"1.After the pH was measured in suspension, the tubes were supercentrifuged atvarying times depending on the solution SAR and Mn concentrations. Manganeseconcentration was determined in the supernatant solution by atomic absorptionspectrophotometry. Statistical analysis was performed by a split design techniquein three replicates, with the SAR as the main treatment and the electrolyteconcentration as the subtreatment. In this experiment, the ionic environment ofthe contact solutions was maintained nearly constant during Mn sorption. Thiswas attained by first equilibrating each sample with a mixed NaCl/CaCl2 electrolytesolution to acquire a certain SAR value and then, during Mn sorption by usingsolutions of varying electrolyte concentrations but of similar SAR. In this way, itwas possible to distinguish between the effects of salinity and sodicity on Mnretention. Previous work neglected the index of sodicity (SAR) when examiningthe effect of electrolyte concentrations (Pasricha and Pennamperuma, 1976), even

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458 EL-AMIN, HUSSEIN, AND EL MAHI

50

40

o

5? 30o3

<D•9 20oV)

•D<

10

0 0.05 0.1 0.15 0.20 .25 .30 0.35

Equilibrium Mn concentration (mg/l)

-3mMpH=8.7 + 2 0 mM pH=8.2 -*"40 mM pH=8.0

-100 mM pH=7.8 "*"200 mM pH=7.6

FIGURE 1. Adsorption isotherms of Mn on Suleimi series equilibrated with differentelectrolyte concentrations at 25 SAR.

when isoequivalent NaCl-CaCl2 mixtures were used at varying electrolyteconcentrations (Khattak and Jarrell, 1988), as SAR depends upon the square rootof equivalent Ca concentration which varies with the variation of (C).

RESULTS AND DISCUSSION

The results show that Mn retention by the three soils equilibrated with saltsolutions can be described by the Fruendlich isotherm. Figure 1 shows a typicalFruendlich plot for S-soil equilibrated at SAR=25. The results for other soils andother SAR values for S-soil are qualitatively similar and are, therefore, not

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SALINITY AND SODICITY ON Mn IN VERTISOLS AND ARIDISOLS 459

TABLE 2. Effect of contact solution composition on the equilibrium manganeseion activity value K (K = pH + '/jlog Mn + '/Slog PC02) in soil suspensions after twohours of shaking. Initial Mn concentration was 4 mg L"1.

Contact solutions

Sodium adsorption ratioElectrolyte concentration(mmolc)SoilsEl HoshEl SuleimiEl Laota

03 200

53 200

253 200

503 200

K0.110.120.11

0.540.390.47

0.770.570.77

0.530.430.66

1.051.151.81

0.530.500.50

1.100.901.40

0.380.380.46

presented. Precipitation of Mn-oxides and MnCO3 is expected in the range ofpH=7.4-9.2 in the present experiment (Pourbaix, 1966). The work of Pasrichaand Pennamperuma (1976) emphasized, however, that in neutral and slightlyalkaline soils Mn solubility is regulated by MnCO3-H2O-CO2 system rather thanMn-oxides.

The calculated potassium (K) value (K=pH + Vilog Mn + Vilog PC02), as listedin Table 2, was found to be much lower than the theoretical K value for MnCO3

equilibrium, which was 4.06 according to Latimer (1952). It seems that theinstantaneous nature of cation adsorption, the low Mn concentrations used in thisexperiment, and the slow rates of reaction of Mn minerals in soils (Pennamperumaet al., 1969), favored Mn adsorption rather than precipitation.

It was noted that Mn adsorption decreased with increasing electrolyteconcentration. The explanation to this effect is that increased competition frombackground cations decreased Mn adsorption. However, the pH was markedlyreduced by increasing electrolyte concentration in all soils and solutions. Forexample, in S soil at SAR=25 (Figure 1), the pH was reduced from 8.7 to 7.6,when the samples were equilibrated with 3 and 200 mmolc, respectively. It wasreported that an inverse relationship existed between pH and the redox potentialin soil (Lindsay, 1979) and reduction of pH is, expected to favor dissolution ordesorptionofMn.

Figure 2 shows the effects of electrolyte concentrations at two different SARvalues on Mn equilibrium concentration at five levels of Mn application. It wasnoted that at the highest electrolyte concentration the equilibrium Mn concentrationwas several times higher than at the lowest electrolyte concentration. This indicatedthat the soil exchange complex had a higher preference for Mn at low electrolyteconcentration and/or high pH relative to the other background content of Na+ andCa^. This was true even when Mn sorption was compared at a concentration of100 and 200 mmolc. Regression analysis of equilibrium Mn content (Figure 2)produced the following relationships:

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460 EL-AMIN, HUSSEIN, AND EL MAHI

5r*g Mn/L

3mg Mn/L

MVL

0.00

SAR=25

5mg Mn/L

3mg Mn/L

1mg Mn/L

0.00O 40 80 120 160 200

Electrolyte concentration (mmol+>

FIGURE 2. The effects of electrolyte concentration on equilibrium Mn concentrationsin Suleimi equilibrated with five Mn concentrations (mg L-1).

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SALINITY AND SODICITY ON Mn IN VERTISOLS AND ARIDISOLS 461

0.35

0.30

O)

E.0.25inco

<0oc8§ 0.15

n= 0.10crUJ

0.05

0.007.2 7.5

• x

7.8

PH

8.1 8.4

L(20) -+-S(20) -*-H(20) — L(100) (100) (100)

FIGURE 3. The effect of pH at two electrolyte concentrations [20 mmol(+) = dottedlines; 100 mmol (+) = solid lines] on the equilibrium Mn concentrations in soils suppliedwith 5 mg I/1.

(1) For Suleimi soil, SAR=0:at 1 mg Mn I/1 added:

Log Mn (mg L-')=log 0.012+0.18 log (C) mmolc (r^O.93)at 5 mg Mn L-1 added:

Log Mn (mg L-')=log 0.035+0.19 log (C) mmolc (r^O.92)(2) For Suleimi soil, SAR=25:

at 1 mg Mn L"1 added:Log Mn (mg L')=log 0.006+0.28 log (C) mmolc (r^O.90)

at 5 mg Mn L'1 added:Log Mn (mg L-')=log 0.02+0.25 log (C) mmolc (^=0.89)

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462 EL-AMIN, HUSSEIN, AND EL MAHI

These equations show that, at a specific SAR, the rate of increase of equilibriumMn was almost constant at the different levels of Mn application.

The effect of pH on equilibrium Mn at different electrolyte concentrationsshowed the equilibrium Mn concentrations to vary between 7.7 to 8.2 in the non-saline and between 7.5 to 7.7 in the saline soil. Sadiq (1981) found no correlationbetween pH and Mn sorption in 27 arid-zone soils. Extrapolation would perhapsproduce at pH>7.8 (Figure 3) and at an electrolyte concentration of 100 mmolc

lower Mn concentration. The present Gezira soils were reported to have varyingsurface charge (Russell, 1973). Barrow (1983) postulated that salinity decreasedthe absolute value of the electric potential in the plane of adsorption which effectedreduction of Mn sorption. Hence, increasing the electrolyte concentration in salinesoils would tend to increase the pH, which perhaps would decrease Mnconcentration in the soil solution.

In conclusion it can be stated that the saline phases of the same soil adsorbedless Mn and had higher equilibrium Mn concentration, whereas the sodic phaseswere characterized by high retention of Mn and low equilibrium concentrations.The effect of sodicity per se was negligible except that at comparatively highSAR, values of Mn retention was increased and the Mn concentrations in solutiondecreased. Salinity tends to alleviate the effects of sodicity on Mn retention, butsoluble salt contents, such as Na2CO3, would decrease Mn availability in salinesoils.

REFERENCES

Adam, A.I., W.B. Anderson, and J.B. Dixon. 1983. Mineralogy of the major soils of theGezira Scheme (Sudan). Soil Sci. Soc. Am. J. 47:1233-1240.

Barrow, N.J. 1983. Testing a mechanistic model X. The effect of pH and electrolyteconcentration on manganese sorption by a soil. J. Soil Sci. 40:427-435.

Chapman, H.D. and P.F. Pratt. 1961. Methods of Analysis for Soils, Plants and Water.Division of Agricultural Science, University of Riverside, Riverside, CA.

El Mahi, Y.E. and M.A. Mustafa. 1980. The effects of electrolyte concentration andsodium adsorption ration on phosphate retention by soils. Soil Sci. 130:321-325.

Holmgren, G.G.S. 1967. A rapid citrate-dithionite extractable iron procedure. Soil Sci.Soc. Am. Proc. 32:210-211.

Khattak, R.A. and W.M. Jarrell. 1988. Salt-induced manganese solubilization in Californiasoils. Soil Sci. Soc. Am. J. 52:1606-1611.

Latimer, W.M. 1952. Oxidation Potentials. 2nd ed. Prentice-Hall, Englewood Cliffs,NJ.

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SALINITY AND SODICITY ON Mn IN VERTISOLS AND ARIDISOLS 463

Leeper, G.W. 1949. The forms and reaction of manganese in the soil. Soil Sci. 63:79-94.

Lindsay, W.L. 1979. Chemical Equilibria in Soils. John Wiley & Sons, New York, NY.

Page, A.L. 1974. Fate and effects of trace elements in sewage sludge when applied toagricultural lands. Soil Sci. Soc. Am. J. 41:1072-1074.

Page, A.L., D.R. Keeney, D.E. Baker, R.H. Miller, R. Ellis, Jr., and J.D. Rhoades. 1982.Methods of Soil Analysis. Part 2. American Society of Agronomy, Madison, WI.

Pasricha, N.S. and F.N. Pennamperuma. 1976. Influence of salt and alkali on ionic equilibriain submerged soils. Soil Sci. Soc. Am. J. 40:374-376.

Pennamperuma, F.N., T.A. Loy, and E.M. Tianco. 1969. Redox equilibria in floodedsoils. II. The manganese oxide systems. Soil Sci. 108:48-57.

Pourbaix, M. 1966. Atlas of Electrochemical Equilibria in Aqueous Solutions. PergamonPress, Oxford, England.

Russell, E.W. 1973. Soil Conditions and Plant Growth. 9th ed. Longman, London,England.

Sadiq, M. 1981. The adsorption characteristics of soils and sorption of copper manganeseand zinc. Commun. Soil Sci. Plant Anal. 12:619-630.

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