Ž.
The Science of the Total Environment 232 1999 185᎐ 191
Concentration and distribution of extractable elements
in a soil as affected by tillage systems and fertilization
R.S. Lavado
U
, C.A. Porcelli, R. Alvarez
Departamento de Suelos, Facultad de Agronomıa, Uni¨ersidad de Buenos Aires, A¨. San Martın 4453, 1417 Buenos Aires,
´´
Argentina
Received 20 September 1998; accepted 21 March 1999
Abstract
Because of crop production intensification, we hypothesize that concentrations of trace elements will increase and
stratify in the soils of the Pampean region. We studied the effects of conventional and zero-tillage and phosphorus
fertilization on concentration and stratification of trace elements in a typical soil of the area. The experiment was
Ž. Ž.
conducted at the Pergamino Agricultural Experimental Station 33Њ56Ј S; 60Њ34Ј W . There were three treatments: i
Ž. Ž. Ž. Ž.
pasture; ii conventional tillage CT ; and iii zero tillage ZT . The crop sequence was wheat, soybean and corn. An
annual average of 90 kg Nrha and 18 kg Prha was applied. Two composite samples of each plot were obtained in
Ž. Ž . Ž .
5-cm increments until 20 cm depth. The soil was characterized and aluminum Al , arsenic As , cadmium Cd ,
Ž. Ž . Ž. Ž. Ž . Ž . Ž . Ž.
chromium Cr , cobalt Co , iron Fe , lead Pb , mercury Hg , manganese Mn , molybdenum Mo , nickel Ni ,
Ž. Ž . Ž.
selenium Se and zinc Zn , were extracted with DTPA and boron B was extracted with hot water. All the element
Ž.Ž.
concentrations were determined with ICP-AES. Concentrations of B av. 0.48 mgrkg , Cd av. 0.20 mgrkg Cr
Ž.Ž .Ž.Ž .
-0.01 mgrkg , Hg -0.005 mgrkg , Mo -0.01 mgrkg , and Se av. 3.33 mgrkg showed no significant differences
Ž.Ž .Ž

Ž.Ž .
time i.e. zero-tillage Singh et al. 1966 . This
stratification process might increase nutrients
Ž
availability and crop absorption Singh et al. 1966;
.
Hargrove 1985 . The two main causes of stratifi-
cation are crop residues accumulation on topsoil
Ž.
and fertilizers application Blevins et al. 1983 .
Ž.
Recently, Scheiner and Lavado 1998 showed
that fertilization is the most important factor for
phosphorus stratification. For some micronutri-
Ž.
ents Cu, Fe, Mn, Zn the stratification was also
Ž.
established Hargrove, 1985; Edwards et al., 1992
but the behavior of other elements is far less
Ž.
known. Oliver et al. 1993 recorded higher Cd
concentrations in wheat under zero tillage, as
compared with minimum or conventional tillage
Ž.
but Cd concentration in soils EDTA extraction
did not show apparent differences under zero-
minimum or conventional tillage.
Trace elements are normally found in phos-
Ž
phate fertilizers Charter et al. 1995; Todorova

soils of the Pampean region Argentina were
carried out with conventional tillage and without
fertilizer from its start, 100r120 years ago. From
the last years, both the use of reduced tillage
systems, including ZT, and phosphate fertilization
are increasing dramatically. The widespread use
of this technology along the time will affect the
soil properties of the region. Among them, we
hypothesize that concentrations of trace elements
will increase and stratify in those soils. However,
as a consequence of the recent introduction of
zero tillage and the lack of fertilization history,
there are no old field experiments in the region
combining tillage and fertilization. With this limi-
tation, our objective was to study the effects of
Ž
two extreme tillage systems conventional and
.
zero-tillage and phosphorus fertilization on con-
centration and stratification of extractable ele-
ments in a representative soil of the Rolling
Pampa, the most productive area of the Pampas.
2. Materials and methods
We worked in an experiment performed at the
Agricultural Experimental Station located in Per-
Ž.
gamino 33Њ56Ј S; 60Њ34Ј W . The soil is a Per-
gamino Series, fine illitic thermic Typic Argiudoll
Ž.
Table 1 . In 1979 three soil treatments started:

Concentration and distribution in depth of organic matter, macronutrients, and other soil components
Ž.
Treatment Depth cm
0᎐ 55᎐10 10᎐ 15 15᎐ 20
OM ZT 3.87 bA 2.73 bB 2.83 bB 2.63 bB
% CT 2.70 cA 2.70 bA 2.80 bA 2.53 bA
Past 6.60 aA 4.10 aB 3.03 bC 2.80 bC
Exchang. ZT 17.67 aA 7.33 bB 7.67aB 6.33 aB
P CT 21.50 aA 17.50 aB 11.50 aC 8.03 aC
ppm Past 13.25 bA 9.75 bB 8.75 aB 8.50 aB
pH ZT 5.10 aA 5.70 aA 5.83 aB 5.93 aB
CT 5.77 bA 5.80 aA 5.80 aA 5.93 aA
Past 5.98 bA 6.10 aA 6.18 aA 6.28 aB
Exchang. ZT 7.35 aA 9.09 aA 9.36 aB 10.14 aB
b
Ca CT 8.53 aA 8.77 aA 8.90 aA 9.41 aA
Past 7.59 aA 8.36 aA 9.10 aA 9.41 aA
Exchang. ZT 1.16 aA 1.40 aB 1.41 aB 1.67 aB
Mg CT 1.49 aA 1.48 aA 1.52 aA 1.81 aB
Past 1.95 bA 1.80 aA 1.64 cA 1.44 aB
Exchang. ZT 0.95 aA 0.93 aA 0.91 aA 0.94 aA
K CT 1.05 bA 1.09 aA 1.06 aA 1.10 aA
Past 1.41 bA 1.61 bA 1.68 bA 1.53 bA
Extract. ZT 7.54 aA 8.07 aA 3.46 aB 3.14 aB
Al CT 4.81 bA 5.51 bA 3.36 aA 3.97 aA
ppm Past 2.30 bA 5.00 bB 2.56 aB 2.48 aB
a
ZT, zero tillage, fertilized; CT, conventional tillage, fertilized; past, pasture, not fertilized. Different small letters mean
Ž. Ž.
significant differences P - 0.05 among treatments. Different capital letters mean significant differences P-0.05 among depths.

.Ž . Ž
mgrkg , Hg in all cases -0.005 mgrkg , Mo in
.Ž
all cases F 0.01 mgrkg , and Se 3.09᎐ 3.57
.
mgrkg exhibited no differences in concentra-
tions among treatments or depths. Cadmium, with
concentrations between 0.17 and 0.23 mgrkg,
showed no differences among treatments but dif-
ferences in depths. The highest Cd concentration
was found on top soil. The remainder trace ele-
ments were affected by the treatments either in
their concentration or in their depth distribution.
Data are shown in Table 2 and Figs. 1᎐3.
Iron and Mn concentrations were higher under
CT but decreased significantly in depth. Zn strati-
fied significantly in both treatments but on topsoil
Ž.
0᎐5 cm showed higher concentration under ZT
and from 5 to 25-cm depth their concentration
()
R.S. La¨ado et al. r The Science of the Total En¨ironment 232 1999 185᎐191188
Table 2
a
Ž.
Concentration and distribution in depth of arsenic, copper, iron, lead and manganese mgrkg
Ž.
Element Treatment Depth cm
0᎐ 55᎐10 10᎐ 15 15᎐ 20
As ZT 0.058 aA 0.058 aA 0.059 aA 0.058 aA

P-0.05 among depths.
()
R.S. La¨ado et al. r The Science of the Total En¨ironment 232 1999 185᎐191 189
Ž. Ž. Ž .
Fig. 2. Concentration and distribution in depth of cobalt in zero-tillage ZT , conventional tillage CT and pasture Past . Different
Ž.
small letters mean significant differences P - 0.05 among treatments. Different capital letters mean significant differences
Ž.
P-0.05 among depths.
concentration decreased under ZT. Edwards et
Ž.
al. 1992 found that Cu was not affected by
tillage or rotations. From the remainder trace
elements, Co and Pb showed significant higher
concentrations on top soil under ZT, but arsenic
and nickel did not show differences related to
tillage systems. Arsenic did not show stratification
but the other trace elements showed a significant
decrease downwards.
Ž.
Shuman and Hargrove 1985 found that the
organic matter accumulation and changes in soil
pH affected the micronutrients distribution and
that Zn was very sensitive to pH changes. Ed-
Ž.
wards et al. 1992 found high lineal relationships
between OM and Mn and Zn concentrations, but
those relations improved when pH was included
Ž.
in the equations. Carter and Gupta 1997 found

behavior: higher concentrations in all depths un-
()
R.S. La¨ado et al. r The Science of the Total En¨ironment 232 1999 185᎐191190
Ž. Ž. Ž .
Fig. 3. Concentration and distribution in depth of nickel in zero-tillage ZT , conventional tillage CT and pasture Past . Different
Ž.
small letters mean significant differences P - 0.05 among treatments. Different capital letters mean significant differences
Ž.
P-0.05 among depths.
der pasture as compared with cropped soils. Per-
haps a remainder of old arsenate, as insecticide,
applied to the pasture.
4. Conclusion
The DTPA extractable trace element concen-
trations are low in general and for some elements
they are around the detection limit. For some
Ž.
trace elements Co, Pb and Zn the extractable
concentration and stratification was linked to OM
and pH. For other elements the behavior observed
in our experiment could not be explained. Surface
concentrations of Co, Cu, Ni and Pb was higher
in cropped soils and this would be accreditable to
fertilizer applications.
Acknowledgements
The research was granted by the National Re-
Ž.
search Council of Argentina CONICET .
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