extractable and total fe and mn contents of three sand dune soils in nw nigeria

Extractable and total Fe and Mn contents of threesand dune soils in NW Nigeria

B. A. Raji*, V. O. Chude* & I. E. Esu†

*Department of Soil Science, Institute for Agricultural Research, AhmaduBello University, Zaria

†Department of Soil Science, University of Calabar, Calabar

(Received 4 October 1997, accepted 11 December 1997)

The profile distribution of total, diethylene triamine penta-acetic acid(DTPA)- and 0·1 M HCl-extractable Fe and Mn were determined in 12pedons formed on three contiguous sand dunes in the semi-arid savanna ofNigeria. The total Fe and Mn contents varied from 100 to 3750 and 40 to11,375 µg g–1, respectively. Values of 0·1 M HCl-extractable Fe and Mnvaried from 8·0 to 123 and 1·5 to 43·5 µg g–1, respectively. The correspondingvalues of DTPA-extractable Fe and Mn were 4·5 to 16·0 and 1·0 to38·8 µg g–1. Total Fe and Mn correlated significantly with clay in nearly all thedunes (p ² 0·01) but were not significantly correlated with organic matter.The 0·1 M HCl-extractable Mn had a positive significant correlation with soilpH (r = 0·58*) in Illela dunes but a negative significant correlation with pHin the Sangiwa dunes (r = –0·75***). The values of extractable Fe and Mn inthe sand dune soils are above the critical limits reported in other literature,thus deficiencies of these micronutrients do not pose a problem to cropproduction in the study area.

©1998 Academic Press Limited

Keywords: total; extractable; sand dune soils; iron; manganese; semi-aridsavanna

Introduction

The problem of micronutrient deficiencies in African soils has increased with the useof more nutrient-demanding crop varieties in place of the tradition fallow system.Current farming practices increasingly depend on fertilizer compounds leading toreports of micronutrient depletion (e.g. Bharadwaji & Omanwar, 1994). In view of themany reports of micronutrient deficiency reported worldwide (Maclean & Langille,1976; Liu et al., 1983; Katyal & Sharma, 1991), but especially for sandy soils and soilswith ustic to aridic moisture regimes (Katyal & Sharma, 1991), a study of NigerianSudano-Sahelian soils is needed.

Previous studies on different locations in Nigeria (Agboola & Corey, 1976; Lombin,1983; Fagbami et al., 1985) have reported deficiencies of micronutrients. Micro-nutrients in the sand dune soils, which are currently extensively cultivated for millet(Pennisetum typhoideum Rich), guinea corn (Sorghum bicolor (L) Moenoh) and cowpea(Vigna unguiculata (L) Walp), need to be quantitatively studied and documented for

Journal of Arid Environments (1998) 38: 585–596

0140–1963/98/040585 + 12 $25.00/0/ae970355 © 1998 Academic Press Limited

proper land use planning and appropriate fertilizer management practices. Theobjective of this study is to determine the extractable and total forms of Mn and Fe insand dune soils in north-western Nigeria.

Material and methods

The soils used in this study were sampled on sand dune parent materials which aredifferentiated into Illela, Sokoto and Sangiwa sand dunes (Sombroek & Zonneveld,1971). Summary of site information and classification of the soils are given in Table1.

Four pedons were selected on each group of dunes, giving a total of 12 pedons (Fig.1). Soil samples from the 12 pedons were analysed for available and total Fe and Mn.Total Mn and Fe contents were measured after NaCO3 fussion (Kanehiro & Sherman,1965). Extraction with DTPA and HCl followed the methods of Lindsay & Norvell(1978) and Osiname et al. (1973), respectively. Fe and Mn were measured usingatomic absorption spectrophotometry (AAS). The physico-chemical properties (pH,organic carbon, clay, oxides of Fe and Al) of the sand dune soils were measured usingstandard methods (Black, 1965).

Results and discussion

The physico-chemical properties of the soils (Table 2) show that the soils were eitherstrongly acidic or near neutral, with organic carbon contents of less than 2·0 g kg–1, andlow contents of clay and oxides of Fe and Al.

Total iron and manganese

Iron

The mean values of total Fe for the Sangiwa dunes were significantly lower (p ² 0·01)than the rest of the dunes. This trend is similar to the trend exhibited by iron oxidesin the dunes (Table 2), and confirmed by the significant correlation between thequantities of FeOX and FeT (Table 3) (subscripts OX and T refer to oxalate-extractableFe and total Fe, respectively). Total Fe contents in the dune soil were lower thanvalues reported by Kparmwang et al. (1995) for basaltic soils in Nigeria (range: 45·0to 97·5 g kg–1) and Katyal & Sharma (1991) for a wide range of soils in India (range:13·2 to 80·0 g kg–1), possibly due to low contents of ferromangnessian minerals. Othersandy soils have being reported to contain very low contents of total and available Feand Mn (Katyal & Randhawa, 1983; Liu et al., 1983).

Manganese

The mean values of total Mn of the three dunes were not significantly different for thesurface soils. In the subsoil, the mean values for Sangiwa dunes were significantlylower (p ² 0·05) than for Sokoto dunes. The total Mn values compared well withvalues reported by Kparmwang et al. (1995) for basaltic soils in Nigeria (range: 40 to1010 µg g–1), Katyal & Sharma (1991) (range: 38 to 1941 µg g–1) for a wide range of

B. A. RAJI ET AL.586

Tab

le 1

.B

asic

site

info

rmat

ion

and

clas

sifica

tion

of th

e so

ils

San

dM

AR

†S

oil

dune

Dun

e fo

rm*

Age

*(m

m)

Lan

d us

e/ve

geta

tion

Dun

e he

ight

clas

sific

atio

n‡

Ille

laF

ortr

ess

5000

500

Shi

ftin

gP

rono

unce

d,U

stic

cult

ivat

ion/

10–2

0 m

hig

hQ

uart

zips

amm

ents

Com

bret

umni

gric

ans,

Ano

geiss

us

Sok

oto

Lon

giti

duna

l20

,000

650

Sem

i-pe

rman

ent

Low

–nea

rly

flat,

Typ

iccu

ltiv

atio

n/A

caci

ale

ss t

han

1 m

Kan

hapl

ustu

lts

albi

da, C

ombr

etum

nigr

ican

s

San

giw

aT

rans

vers

al15

0,00

060

0V

irgi

n to

shi

ftin

gM

oder

ate,

Ust

iccu

ltiv

atio

n/C

ombr

ele

ss t

han

3 m

Qua

rtzi

psam

men

tstu

m n

igri

cans

*Som

broe

k &

Zon

evel

d (1

971)

.†M

AR

=m

ean

annu

al r

ainf

all (

Row

al &

Kno

ble,

197

2).

‡Soi

l Sur

vey

Sta

ff (

1994

).

MINERAL CONTENTS OF SAND DUNES 587

soils in India, and McNeal et al. (1985) (range: 220 to 890 µg g–1) for some soils in theNorthern Great Plains of the United States.

0·1 M HCl-extractable iron and manganese

Iron

The means of HCl-extractable Fe (FeH) were not significantly different betweendunes. These values compared well with values reported for basaltic soils in Nigeria(Kparmwang et al., 1995) (range: 15·0 to 66·3 µg g–1). These values were, however,higher than values reported by McNeal et al. (1985) for soils from the Northern GreatPlains of the United States. There was a decrease of FeH down the profile with the

14°00' N

13°00'

13°30'

5°00' E 5°30'

S1

BodingaDanchadi

SOKOTODubawa

Dange

Kirare

Bijeje

G1

G4G2

SalameS3

S4Kwarne

GidanMakama

Gwabawa

Rako

Sauna

Tungan TudaAsaraL4

L3Tundu Mulata

Gidan KataGaidau

DanbakoIllela

Kalmalo

RIVER

RIM

A

RIVER SOKOTO

L1L2

G3

S2

14°N

10°

6°

14°E10°6°

Study area

Illela dunesKey

Sokoto dunesSangiwa dunesState CapitalTowns and villagesRoadsRiversLocation of pedons

S2

N

10 0 10 20 km

Figure 1. Distribution of sand dunes around Sokoto, north-western Nigeria and the location ofthe pedons studied.


Tab

le 2

.M

ean

valu

es o

f sel

ecte

d so

il pr

oper

ties

for

the

soils

Org

anic

Tex

ture

(%

)F

e-ox

ides

(%

)A

l oxi

des

(%)

pHca

rbon

Dun

e ty

peH

2OC

aCl 2

(g k

g–1 )

San

dS

iltC

lay

Fe d

Fe o

xF

e pA

l dA

l ox

Al p

Ille

la d

unes

Sur

face

5·8

4·9

0·9

941

50·

670·

100·

010·

880·

730·

12ho

rizo

nsS

ubso

il6·

25·

10·

591

17

0·54

0·14

0·01

0·58

1·05

0·34

hori

zons

Sok

oto

dune

sS

urfa

ce5·

64·

21·

489

29

0·60

0·16

0·02

1·17

0·88

0·47

hori

zons

Sub

soil

5·0

3·4

0·8

754

211·

310·

250·

030·

881·

170·

33ho

rizo

ns

San

giw

a du

nes

Sur

face

5·4

5·2

1·1

907

30·

170·

070·

010·

740·

730·

43ho

rizo

nsS

ubso

il4·

23·

40·

580

1010

0·34

0·08

0·08

1·14

1·02

0·29

hori

zons

*Fe d

=to

tal f

ree

iron

oxi

des;

Fe o

x=

oxal

ate-

extr

acta

ble

iron

oxi

des;

Fe p

=py

roph

osph

ate-

extr

acta

ble

iron

oxi

des.

Al d

=to

tal f

ree

alum

iniu

m o

xide

s; A

l ox=

oxal

ate-

extr

acta

ble

alum

iniu

m o

xide

s; A

l p=

pyro

phos

phat

e-ex

trac

tabl

e al

umin

ium

oxi

des.


highest values in the AC and AB horizons, indicating that no single pedogenic processcontrols this distribution.

Manganese

The mean values of HCl-extractable Mn (MnH) were not statistically different in thesurface horizons, but in the subsoil the mean for Illela was significantly lower(p ² 0·01) than the means for Sokoto and Sangiwa dunes (Table 4). The lower MnH

values in the subsoil horizons of the Illela dunes are probably due to the alkaline soilreaction since MnH has a negative correlation with soil pH. The MnH values decreaseddown the profile, indicating a greater contribution of MnH by organic matter. TheMnH values were slightly lower than those reported by Kparmwang et al. (1995) forbasaltic soils in Nigeria (range: 17·1 to 83·3 µg g–1). Shuman et al. (1980) reported avalue of 2·6 µg g–1 as the critical limit for extractable manganese in soils. Using thisvalue, deficiency of manganese in unlikely in these soils, except possibly in the Illeladunes.

DPTA-extractable iron and manganese

Iron

The mean values of DTPA-extractable Fe (FeD) were not significantly differentbetween dunes. The values are within the range for basaltic soils in Nigeria

Table 3. Correlation between micronutrient Fe and Mn with selected soil properties

FreeClay pH OC CEC carbonate Feox Fed Alox Ald

Illela dunesFeH – * – ** – * ** – –FeD – – – – – – – – –FeT ** – – – * – ** – –MnH – * ** – – * – – *MnD – *** – * – * – – –MnT * – – – * – – – –

Sokoto dunesFeH – – * – – – – – –FeD – – – – – – – – *FeT ** – – ** – ** – ** –MnH – – – – – * – ** –MnD * – – ** – ** * *** *MnT – – – ** – *** * *** *

Sangiwa dunesFeH – – – –* – – –* – –FeD ** –* – * – – – – –FeT * – –* *** * – – – –MnH – –* – – – – – – –MnD ** –*** – * – – – – –MnT ** – – *** – – – – –

–=not significant at p=0·05; *=significant at p=0.05; **=significant at p=0.01; ***=significant atp=0·001.


Table 4. Total and available forms of Fe and Mn (cont.)

Iron (µg g–1) Manganese (µg g–1)

Extractable ExtractableDepth

Horizon (cm) DPTA HCl Total DPTA HCl Total

Illela dunesPedon L1

AP 0–28 7·5 11·7 1200·0 4·0 7·5 70·0AC 28–63 10·3 8·3 1250·0 3·2 6·9 325·0C1 63–142 10·3 23·7 2687·5 2·6 4·5 725·2C2 142–175 12·0 30·0 1687·5 1·6 3·0 425·1

Pedon L2Ap 0–18 5·9 19·2 1900·0 4·0 8·7 625·0AB 18–52 8·0 16·5 762·5 1·0 5·1 75·5Bt1 52–95 9·1 30·0 3600·0 1·6 3·3 725·0Bt2 95–170 5·5 17·0 3137·5 1·8 1·5 625·0

Pedon L3Ap 0–27 6·7 57·8 3100·0 10·4 27·6 725·0AC 27–73 12·0 62·7 2250·0 9·5 18·0 355·0C1 73–130 7·0 63·2 4250·0 8·4 18·0 1025·0C2 130–210 8·5 90·0 1937·5 6·6 15·0 375·1

Pedon L4Ap 0–12 5·1 45·0 1625·0 12·8 37·5 475·1AC 12–60 11·5 34·2 500·0 10·8 15·0 175·0C1 60–100 8·7 30·0 1812·5 9·4 15·6 525·0C2 100–140 6·0 38·3 437·5 6·0 11·7 205·5C3 140–190 5·1 31·7 387·5 3·2 6·0 125·0

Sokoto dunesPedon S1

Ap 0–22 9·6 33·0 1062·5 22·0 24·0 40·0AB 22–39 13·1 23·3 1400·0 8·4 9·9 275·2Bt1 39–56 8·9 18·8 1937·5 16·6 16·5 415·0Bt2 56–85 5·9 28·2 3750·0 17·6 18·0 1025·0Bt3 85–105 4·5 30·0 3500·0 24·8 25·5 940·0

Pedon S2Ap 0–15 9·9 23·2 1437·5 19·8 21·0 355·0AB 15–26 10·0 23·6 1937·5 7·1 7·5 440·5Bt1 26–52 5·7 20·3 1687·5 17·6 18·0 325·0Bt2 52–80 6·0 15·0 1562·5 20·8 22·5 390·0Bt3 80–95 5·5 21·8 2312·5 26·0 28·5 550·2

Pedon S3Ap 0–15 6·0 47·3 2475·0 14·4 37·5 750·0Bt 15–40 16·0 60·0 2875·0 32·8 43·5 1375·0

Pedon S4Ap 0–15 6·0 36·8 1187·5 12·0 30·0 525·2AC 15–35 8·0 36·8 1137·5 11·4 19·5 475·5C1 35–60 8·0 38·3 900·0 12·8 18·0 325·0


(Kparmwang et al., 1995). All the soils had available Fe contents higher than thecritical level of 4·5 µg g–1 quoted by Lindsay & Norvell (1978). Iron deficiency inducedby zinc levels as low as 10–1

M (6 µg g–1) has, however, been documented (Wallace etal., 1976). Such levels of available zinc are present mainly on the Illela dunes (Raji etal., 1996) and as such, deficiency of iron induced by zinc is only likely on the Illeladunes.

Manganese

The mean values for the Sokoto dunes were significantly higher (p ² 0·01) than themeans for the Illela dunes, both in the surface and subsoil horizons (Table 4). Thelower values on the Illela dunes are mainly due to their alkaline soil reaction, sincemanganese becomes unavailable to plants at high pH (Tisdale et al., 1985). The MnD

values were higher than those reported for granitic soils (Mosugu, unpublished)(range: 0·40 to 40 mg kg–1) but were comparable to values reported for some soils inthe United States by Salcedo & Warncke (1979) (range: 0·71 to 42·5 µg g–1) andMcNeal et al. (1985) (range: 1·1 to 15 µg g–1), and slightly lower than values reportedby Kparmwang et al. (1995) (range: 3·0 to 114·7 µg g–1) for basaltic soils in Nigeria.

Table 4. Continued

Iron (µg g–1) Manganese (µg g–1)

Extractable ExtractableDepth

Horizon (cm) DPTA HCl Total DPTA HCl Total

2C2 60–115 9·4 42·8 1525·0 14·0 22·5 625·02C3 115–180 10·5 123·8 1037·5 21·6 25·5 495·1

Sangiwa dunesPedon G1

Ap 0–33 5·0 31·5 187·5 8·8 22·5 50·0AC 33–65 5·2 21·8 562·5 12·4 18·0 70·0C1 65–108 4·8 14·3 150·0 17·6 22·5 105·0C2 108–185 4·9 30·0 812·5 21·6 26·4 65·5

Pedon G2Ap 0–24 4·0 23·3 100·0 11·2 17·1 40·0AC 24–45 6·7 23·7 187·5 17·0 20·4 60·0C1 45–100 6·8 24·8 687·5 30·4 34·5 375·2C2 100–190 8·3 22·2 750·0 38·8 43·5 355·0

Pedon G3Ap 0–21 6·0 30·0 562·5 16·0 24·3 210·0AC 21–50 8·0 8·3 1062·5 17·6 23·7 325·2C1 50–110 6·7 8·0 1312·5 24·8 27·0 390·0C2 110–160 6·0 18·2 1012·5 12·8 19·2 330·1

Pedon G4Ap 0–30 4·2 14·6 437·5 12·8 22·5 150·0AC 30–60 8·0 12·8 725·0 13·2 16·5 190·0C1 60–110 6·3 20·7 912·5 27·2 27·0 300·0C2 110–160 8·0 19·8 925·0 29·6 30·0 340·2


The MnD values were generally much higher than the critical limit of 1·0 µg g–1 quotedby Lindsay & Norvell (1978).

Relationship between forms of Fe and Mn

The available forms of Fe did not correlate with one another and with the total formin all the dunes except in the Sangiwa dunes (Table 5). This points to possibleextraction of the forms of Fe from different sources, as reported by McNeal et al.(1985) for some soils in the United States. Lack of association between the total formand the available forms of Fe may indicate that the availability of Fe in the soils isdependent upon factors other than total Fe contents (Follet & Lindsay, 1970).

In all the dunes, DTPA- and HCl-extractable Mn were positively correlated withone another (Table 5) suggesting that they are from the same source. This is inconformity with the findings of Kparmwang et al. (1995) for basaltic soils in Nigeria,but contrary to the reports of McNeal et al (1985) for some soils in the U.S.A. andKatyal & Sharma (1991) for some Indian soils. The available forms of Mn werepositively correlated with total Mn in the Illela and Sokoto dunes, suggesting aconsiderable labile pool of Mn to replenish available forms. Shuman & Anderson(1974) have also reported such a relationship between the available and total forms ofMn.

Total Fe and Mn measurements were positively and significantly correlated with oneanother (Table 5). This may indicate that while the available forms might be fromdifferent sources, the bulk of the total Mn and Fe comes from a similar source.

Table 5. Correlation matrix between and within forms of Fe and Mn

FeH FeD FeT MnH MnD MnT

Illela dunesFeHFeD –FeT – –MnH * – –MnD – – – **MnT – – *** – –

Sokoto dunesFeHFeD –FeT – –MnH – – –MnD – – – **MnT – – *** * *

Sangiwa dunesFeHFeD –FeT – *MnH – – –MnD – * – ***MnT – ** *** * **

–=not significant at p=0·05; *=significant at p=0·05; **=significant at p=0·01;***=significant atp=0·001.


Relationships between forms of Fe and Mn with soil properties

Total Fe and Mn were positively correlated with clay in all the dunes except in theSokoto dunes (Table 3). Only the DTPA-extractable Fe and Mn correlated with clayin the Sangiwa dunes and MnD in the Illela dunes, suggesting that clay content doesnot play a major role in the retention and availability of these micronutrients except onthe Sangiwa dunes.

Total Fe and Mn were not correlated with pH in all the dunes (Table 3). Katyal &Sharma (1991) and Kparmwang et al. (1995) have also reported a non-significantcorrelation between total forms of Fe and Mn, and pH. The available forms of Fe andMn, however, correlated with pH in some dunes. Correlation between pH and theavailable forms of Fe and Mn in the Sangiwa dunes were negative in all instances, buton the Illela dunes pH was positively correlated with the available forms of Fe and Mn.These differences may be ascribed to differences in the pH, being less than 5·0 onSangiwa dunes and ranging from 6·3 to 8·0 on Illela dunes. Significant positivecorrelation was also observed between the total forms of Fe and Mn with free calciumcarbonate and clay in the Illela dunes, suggesting that the total forms occur ascarbonate minerals, perhaps clay-sized. The association of pH and free carbonate withtotal forms suggests that with an increase in pH, more of the available Fe and Mn heldby carbonate minerals are made available in the Illela dunes but the converse is the casein the Sangiwa dunes.

Organic matter was not significantly correlated with forms of Fe and Mn. Thisfinding is contrary to the findings of McNeal et al. (1985), Katyal & Sharma (1991)and Kparmwang et al. (1995). The non-significant contribution of organic matter tothe retention and release of Fe and Mn in sand dune soils may be attributed to the verylow contents of organic carbon ( < 2·0 g kg–1).

Soils of the Sokoto dunes were classified as Ultisols while soils of Illela and Sangiwadunes were classified as Entisols. The lack of significant differences between thecontents of available forms of Fe and Mn in most cases, therefore, suggest that in theSokoto dunes a large proportion of the available forms probably occur in the occuledform.

Conclusion

The sand dune soils in north-western Nigeria are found to have an appreciable contentof total Fe and Mn and a sufficient amount in available forms. This tends to suggestthat Fe and Mn fertilization might presently not be necessary for optimum cropproduction within the area. However, in the near future, such application mightbecome necessary on soils of Illela dunes where soil reaction is close to neutral. A largeproportion of the total Fe form is, however, unavailable as shown by the lack ofcorrelation between this and available forms. However, appreciable replenishment isexpected from the total Mn to the available Mn forms because of the significantcorrelation (p ² 0·05) between them.

In the three sand dune soils studied, only a few of the properties examined weresignificantly different: available and total manganese. A possible explanation for thesedifferences could be ascribed to the differences in soil pH. There were differences inthe relationship between pH and the forms of Fe and Mn in the three dunes; nosignificant correlation in the Sokoto dunes, negative correlation in the Sangiwa dunes,and positive correlation in the Illela dunes. This signifies the need for different fertilitymanagement practices for the dune soils.

To enhance the productivity of Illela soils, which are neutral in reaction, and thusensure high economic returns from crop production, farmers would be required toapply acidifying fertilisers (e.g. sulphate of ammonia). Use of lime in the form of


limestone, which is locally available, on soils of Sangiwa dunes which are strongly acidis proposed as an amendment. However the use of lime is not part of the currentfarming practice in the area.

The apparent lack of significant differences in most of the properties studied mightbe explained by the similar environmental conditions and parent materials, whichaccording to Sombroek & Zonneveld (1971) were reworked from one another.

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extractable and total fe and mn contents of three sand dune soils in nw nigeria

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