Extractable forms of aluminum as affected by gypsum and lime amendments to an acid soil


Vizcayno, C.G.rcia-Gonzalez, M.; Fernandez-Marcote, Y.S.ntano, J.

Communications in Soil Science and Plant Analysis 2(13-14): 2279-2292

2001


The influence of gypsum or lime + gypsum amendments on various extractable forms of aluminum (Al) in a reconstructed acid soil (plinthic Palexerult) was investigated. The addition of gypsum depolymerized non-hydrolysable carbon (C) and increased the extraction of Al bound to organic matter. The application of gypsum or lime + gypsum lowered the levels of exchangeable Al; also, the low proportion of Al in outflow solutions suggests the immobilization of Al as a solid phase. Except for exchangeable Al, the gypsum amendment increases the proportion of all forms of Al extracted (bound to organic matter, sorbed to, oxalate and citrate) with various selected reagents relative to unamended samples. The amount of Al extracted increases with increase of gypsum added. The gypsum or lime + gypsum amendments increased soil productivity.

COMMUN.
SOIL
SCI.
PLANT
ANAL.,
32(13&14),
2279-2292
(2001)
EXTRACTABLE
FORMS
OF
ALUMINUM
AS
AFFECTED
BY
GYPSUM
AND
LIME
AMENDMENTS
TO
AN
ACID
SOIL
Carmen
Vizcayno,
14
Maria
Teresa
Garcia-Gonzalez,'
Yolanda
Fernandez-Marcote,'
and
Jesus
Santano
2
1
Departamento
de
Suelos,
Centro
de
Ciencias
Medioambientales,
CSIC,
Serrano
115,
E-28006
Madrid,
Spain
2
Departamento
de
Edafologia,
Escuela
Tecnica
Superior
de
Ingenieros
AgrOnomos,
Ciudad
Universitaria,
E-28040
Madrid,
Spain
ABSTRACT
The
influence
of
gypsum
or
lime
+
gypsum
amendments
on
various
extractable
forms
of
aluminum
(Al)
in
a
reconstructed
acid
soil
(plinthic
Palexerult)
was
investigated.
The
addition
of
gypsum
depolymerized
non-hydrolysable
carbon
(C)
and
increased
the
extraction
of
Al
bound
to
organic
matter.
The
application
of
gypsum
or
lime
+
gypsum
lowered
the
levels
of
exchangeable
Al;
also,
the
low
proportion
of
Al
in
outflow
solutions
suggests
the
immobilization
of
Al
as
a
solid
phase.
Except
for
exchangeable
Al,
the
gypsum
amendment
increases
the
proportion
of
all
forms
of
Al
extracted
(bound
to
organic
matter,
sorbed
to,
oxalate
and
citrate)
with
various
selected
reagents
relative
to
unamended
samples.
The
amount
of
Al
extracted
increases
with
increase
of
*Corresponding
author.
E-mail:
cvizcayno@ccma.sic.es
2279
Copyright
©
2001
by
Marcel
Dekker,
Inc.
www.dekker.com
2280
VIZCAYNO
ET
AL.
gypsum
added.
The
gypsum
or
lime
+
gypsum
amendments
increased
soil
productivity.
INTRODUCTION
Aluminum
is
the
most
abundant
metallic
element
in
soils.
The
effects
of
Al
on
the
properties
and
behavior
of
soil
arise
from
various
phenomena
that
depend
on
the
specific
form
of
the
element
in
soil.
Thus,
soluble
or
easily
extracted
Al
forms
have
phytotoxic
effects.
Interlayered
hydroxy
Al
compounds
in
clay
minerals,
amorphous
hydrous
oxides
associated
with
clay
surfaces
and,
possibly,
Al
organic
complexes
may
play
prominent
roles
in
the
retention
of
anions
and
cations,
the
lowering
of
the
cation-exchange
capacity,
soil
aggregate
stability,
and
other
physical
properties
such
as
infiltration
rate
and
water
retention.
The
efficiency
of
gypsum
and
lime
as
ameliorants
for
soil
acidity
has
been
demonstrated
by
many
authors
(1,2);
their
addition
leads
to
substantially
increased
yields
in
a
wide
variety
of
crops.
This
effect
is
usually
due
to
an
increased
supply
of
Ca
and
a
decreased
level
of
exchangeable
Al
in
the
soil,
both
of
which result
in
improved
root
proliferation
in
the
subsoil
and
in
increased
availability
of
water.
However,
very
little
is
known
about
the
effect
of
gypsum
and
lime
on
other
forms
of
Al
also
present
in
the
soil.
This
interest
prompted
us
to
undertake
the
present
work.
MATERIALS
AND
METHODS
The
study
was
carried
out
on
a
plinthic
Palexerult
soil
from
the
Canameros
"rafia",
a
geomorphological
surface
developed
over
continental
sediments
during
the
Middle
to
Upper
Pliocene
that
was
exposed
to
a
climate
with
warm,
wet
summers
prior
to
the
Pleistocene.
The
soil
is
acid,
has
a
low
organic
matter
content,
is
very
stony
(especially
on
the
surface),
and
also
is
highly
weathered.
It
was
useless
for
cropping
purposes,
mainly
because
of
Al
toxicity
in
addition
to
considerable
calcium
(Ca)
and,
possibly,
magnesium
(Mg)
deficiencies.
The
most
salient
features
of
the
soil
profile
are
in
Table
1.
A
height
of
1
m
of
the
profile
was
reconstructed
in
PVC
columns
of
5
cm
internal
diameter,
using
the
horizon
thickness
and
bulk
densities
of
the
natural
earth
from
the
Ap,
AB,
and
Bt1
horizons
(1.6,
1.3,
and
1.2
g
cm
-3
,
respectively).
Two
columns
were
washed
weekly
with
200
mL
of
deionized
water
(unamended
sample,
CO).
Volumes
of
200
mL
of
a
2
g
L
-1
gypsum
solution
were
added
on
a
weekly
basis
until
a
rate
of
20
or
40
t
ha
-1
was
reached
(columns
Cl,
C3
and
duplicates
of
both). Samples
from
the
Ap
horizon
were
supplied
with
lime
at
a
rate
of
17.5
t
ha
-1
and
incubated
for
5
weeks
with
wetting
to
field
capacity;
this
EXTRACTABLE
FORMS
OF
ALUMINUM
2281
Table
1.
Main
Morphological
and
Chemical
Characteristics
of
the
Soil
Profile
pH
Sand
Silt
Clay
Depth
OM
Horizon
cm
Color
H
2
O
CaCl
2
g.kg
-1
g.kg
-1
Ap
0-33
10YR3/2.5
5.1
4.3
29.9
692
250
58
AB
33-56
10YR5/5
4.9
4.3
5.4
558
221 221
Bt1
56-100
7.5YR5.5/6
4.8
4.3
4.0
509
167
324
Bt2
100-210
2.5YR4/7
4.8
4.2
nd
483
104
413
nd:
not
determined.
new
Ap
horizon
was
used
to
prepare
soil
column
C5
and
its
duplicate.
To
these
last
columns,
30
t
of
gypsum
ha
-1
were
also
added.
Following
gypsum
additions,
each
soil
column
was
supplied
with
200
mL
of
deionized
water
on
a
weekly
basis.
Leaching
was
terminated
when
the
EC
of
the
leachate
was
constant
(0.2
dS
m
-1
).
The
amount
of
supplied
water
was
equivalent
to
2.5
rainfall
years
(the
average
annual
precipitation
in
the
area
is
about
900
mm).
The
outflow
solutions
of
the
treatments
and
leachates
were
analyzed
for
sodium
(Na),
potassium
(K),
and
Ca
(flame
photometry);
Mg
and
Al
(atomic
absorption),
silicon
(Si)
(ICP
spectroscopy);
and
EC
(conductimetry).
After
the
leaching
treatments
were
completed,
the
soil
columns
were
air-
dried
to
a
degree
permitting
collection
of
soil
samples.
The
soil
columns
were
exposed
into
halves
by
sawing
the
PVC
cylinders
vertically;
from
the
exposed
columns,
the
corresponding
horizons
(Ap,
AB,
and
Bt1)
were
sampled.
These
samples
were
air-dried
prior
to
analyzing
the
fractionation
of
Al
as
exchangeable,
bound
to
organic
matter,
sorbed,
and
oxalate,
citrate
(3)
and
dithionite-citrate-
bicarbonate
(dcb)
(4)
extractable,
determining
exchangeable
cations,
and
organic
matter,
and
examining
by
X-ray
diffraction.
Minerals
were
identified
by
using
a
Philips
X'Pert
diffractometer.
Semi-
quantitative
estimates
for
the
minerals
were
obtained
from
XRD
random
powder
and
oriented
aggregate
patterns,
using
the
intensity
factors
reported
by
Schultz
(5).
For
each
horizon,
the
whole
sample
(.2
mm)
and
the
clay
fraction
(.2
ilm)
extracted
by
sedimentation,
were
studied.
Total
carbon
was
determined
by
using
a
Strohlein
CS-MAT
550
automatic
analyzer
and
the
fractional
composition
of
humus
by
the
modified
method
of
Tiurin
(6).
Productivity
tests
were
carried
out
on
pots
where
the
soil
profile
corresponding
to
the
Ap
(200
g
of
the
.
2
mm
fraction)
and
AB
(100
g
of
the
.2
mm
fraction)
horizons
was
reconstructed;
the
pots
were
subjected
to
the
same
2282
VIZCAYNO
ET
AL
treatments
applied
to
the
columns
(viz.
gypsum
at
20
and
40
t
ha
-1
and
incubation
with
17.8t
lime
ha
-1
prior
to
addition
of
30t
gypsum
ha
-1
).
From
each
experiment
four
replicates
were
prepared
using
the
appropriate
amounts
of
(N
1-1
4)
11
2PO4,
NI
-
14NO3,
KNO
3
and
urea
as
fertilizers.
The
productivity
was
evaluated
in
terms
of
seed
nascence
and
leaf
and
root
weight
using
Raphanus
sativus.
Cl
and
C3
50
50
-4,-Mg
40
40
-A-Al
Na
30
30
-e-
Ca/10
L
Si
C)
\
\\9.e‘slao
K
.0
20
10
20
10
0
0
0
10
20
30
40
0
50
100
150
200
250
C5
50
50
40
40
30
30
r
g
20
20
10
10
0
10
20
30
40
0
50
100
150
200
250
t
gypsum
ha"
1
mL
H
2
O
oin
Figure
I.
Chemical
analysis
for
Mg,
K,
Al,
Na,
Ca,
and
Si,
in
the
outflow
solutions
of
treatments
and
leachates.
Cl
samples
treated
with
20
t
gypsum
ha
-1
;
C3
samples
treated
with
40
t
gypsum
ha
-1
;
C5
samples
treated
with
17.5
t
lime
ha
-1
+30
t
gypsum
ha-1.
EXTRACTABLE
FORMS
OF
ALUMINUM
2283
RESULTS
AND
DISCUSSION
The
chemical
analysis
of
the
leachates
from
the
columns
and
those
resulting
from
the
washing
process
following
gypsum
(columns
Cl
and
C3)
and
lime
+
gypsum
(column
C5)
addition
(Fig.
1)
provided
similar
results.
Sodium
was
the
first
leached
element;
its
concentration
in
the
leachate
peaked
at
an
amount
of
gypsum
added of
about
10
t
ha
-1
.
Silicon,
Mg,
and
Ca
leaching
started
at
a
gypsum
rate
about
15
t
ha
-1
.
The
highest
concentration
of
leached
Mg
(45
mg
1
-1
)
was
obtained
with
gypsum
added
at
20
t
ha
-1
rate.
The
addition
of
lime
lowered
the
concentration
of
Mg
in
the
leachate
to
36
mg
1
-1
.
The
lime
+
gypsum
accelerated
the
Si
concentration
peak
in
the
leachate
(at
20
t
gypsum
ha
-1
)
relative
to
the
addition
of
gypsum
(28
t
ha
-1
)
alone;
however,
the
highest
leached
concentration
was
the
same
in
both
cases
(15
mg
1
-1
).
The
amount
of
leached
Ca
increased
with
the
addition
of
gypsum
or
lime+gypsum;
this
dependence
takes
place
up
to
26
or
28
t
gypsum
ha
-1
,
respectively.
Aluminum
and
potassium
were
leached
in
small
constant
amounts
throughout
the
treatments.
A
comparison
of
the
results
of
the
organic
matter
determination
for
the
Ap
horizon
in
the
unamended
sample
(Fig.
2,
column
CO)
and
the
same
sample
following
addition
of
gypsum
(column
C3)
reveals
that
gypsum
decreased
the
amount
of
total
C
that was
leached
from
the
profile
(the
outflows
of
the
first
few
treatments
were
colored).
The
treatment
gave
rise
to
a
decrease
in
the
content
in
unhydrolyzed
C
and
hence
raised
the
proportion
of
humic
acids.
The
addition
of
lime+gypsum
caused
no
appreciable
change
in
the
total
C
content
(Fig.
2);
however,
it
lowers
the
unhydrolyzed
C
content
relative
to
the
unamended
sample;
in
this
case,
the
proportions
of
humic
and
fulvic
acids
increased
to
a
similar
extent.
The
addition
of
gypsum
lowered
the
pH
and
increased
exchangeable
Ca
levels
and
the
effective
cation
exchange
capacity
in
all
horizons
relative
to
the
unamended
samples
(Table
2).
The
amount
of
exchangeable-Al
in
all
horizons
after
the
gypsum
amendments
diminished
in
comparison
to
the
unamended
samples
(Fig.
3,
columns
C1
and
C3).
In
the
Ap
horizon
the
amount
of
Al
extracted
decreased
with
increase
the
amount
of
gypsum
added;
in
the
other
horizons,
there
was
no
relationship
between
those
variables.
As
a
result,
the
Ca
/A1
ratio
was
increased,
the
effect
being
proportional
to
the
gypsum
amount
added.
Exchangeable
Mg
was
removed
in
substantial
amounts
from
the
Ap
horizon
and
accumulated
in
the
AB
and
Btl
horizons.
The
addition
of lime+gypsum
to
the
Ap
horizon
increased
the
pH
and
Mg,
Na,
and
K
losses
to
a
greater
extent
than
the
addition
of
gypsum
alone
(Table
2);
there
was
no
Al-exchangeable
extracted
(Fig.
3,
column
C5).
Lime
had
less
marked
effects
on
the
AB
and
Btl
horizons,
where
the
amounts
of
exchangeable
cations
(Mg,
Na,
and
K)
and
the
pH
were
similar
and
the
exchangeable
Al
decreased
in
comparison
with
the
unamended
samples.
2284
VIZCAYNO
ET
AL
1,5
1
0,5
o
Total
Unhydr
FA
HA
Figure
2.
Organic
carbon
determinations:
Total,
non-hydrolysed
(Unhydr),
fulvic
(FA),
and
humic
(HA)
acids.
As
a
percentage
of
the
whole
fraction
(2mm).
CO
unamended
samples;
C3
samples
treated
with
40
gypsum
t
ha
-1
;
C5
samples
treated
with
17.5
t
lime
ha
-1
+30
t
gypsum
ha
-1
.
Table
2.
pH,
Exchangeable
Cation
Contents,
and
Effective
Cation
Exchange
Capacity
(CECe)
[cmol
(+)
kg
-1
]
of
the
Soil
Horizons
for
Unamended
and
Amended
Samples
Horizon
Sample
pH
Ca
2+
Mg
2+
Na
+
IC
+
Al
3+
Ca
2+
/A1
3+
CECe
Ap
CO
5.1
0.72
0.25
0.08
0.08
1.67
0.43
2.80
Cl
4.8
1.90
0.12
0.07
0.05
1.48
1.28
3.62
C3
4.5
2.70
0.10
0.05
0.03
1.30
2.10
4.18
C5
5.9
4.87
0.09
0.04
0.03
0.00
-
5.03
AB
CO
4.9
0.35
0.12
0.07
0.08
1.48
0.24
2.10
Cl
4.8
0.65
0.15
0.08
0.12
1.30
0.50
2.30
C3
4.6
1.15
0.15
0.09
0.10
1.30
0.88
2.79
C5
4.9
1.18
0.13
0.09
0.12
0.56
2.11
2.08
Bt1
CO
4.8
0.77
0.12
0.09
0.10
2.22
0.35
3.30
Cl
4.7
1.00
0.16
0.08
0.12
1.30
0.77
2.66
C3
4.7
1.20
0.18
0.09
0.12
1.30
0.93
2.89
C5
4.8
1.15
0.14
0.08
0.12
1.48
0.77
2.97
CECe
obtained
as
KC1
extractable
acidity
+
exchangeable
Ca,
Mg,
Na
and
K.
CO
unamended
samples;
Cl
samples
treated
with
20t
gypsum
ha
-1
;
C3
samples
treated
with
40
t
gypsum
ha
-1
;
C5
samples
treated
with
17.5
t
lime
ha
-1
+30
t
gypsum
ha-1.
0
OCO
OC3
005
EXTRACTABLE
FORMS
OF
ALUMINUM
exchangeable
Al
Al
bound
to
organic
matter
cmol
(+)
/
kg
cmol
(+)
/
kg
2285
3/
2.5
5
2
4
1.5
3
2
0,5
1
0
CO
C1
C3
C5
/*
0
CO
Cl
C3
C5
sorbed
Al
oxalate-extractable
Al
crnol(+)
/
kg
cmoim
/
kg
14
60
2
50
10
40
30
20
0
o
/
0
/
CO
C1
C3
C5
CO
C1
C3
C5
citrate-extractable
Al
dcb-extractable
Al
cmol(+)
/
kg
cmol(-0
/
kg
100
100
80
80
60
60
40
40
20
20
0
0
CO
C3
C5
CO
C1
C3
C5
Figure
3.
Different
forms
of
extracted
aluminum.
CO
unamended
samples;
Cl
samples
treated
with
20
t
gypsum
ha
-1
;
C3
samples
treated
with
40
t
gypsum
ha
-1
;
C5
samples
treated
with
17.5
t
lime
ha
-1
+30
t
gypsum
ha
-1
.
The
amount
of
Al
bound
to
organic
matter
(extracted
by
CuC1
2
+
KC1)
before
or
after
the
gypsum
amendment
(Fig.
3)
depended
on
the
organic
matter
content
of
each
horizon.
In
all
horizons,
increasing
the
gypsum
application
rate
increased
the
amount
of
Al
extracted.
In
column
C5,
the
addition
of
17.5
t
lime
ha
-1
+30
t
gypsum
ha
-1
,
resulted
in
a
sharp
decrease
in
the
amount
of
Al
extracted
from
de
Ap
horizon
relative
to
the
addition
of
gypsum
alone.
No
similar
effect
was
observed
on
the
AB
and
Bt1
horizons.
It
is
worth
noting
the
large
amounts
of
sorbed
Al
(extracted
by
NH
4
acetate)
from
the
unamended
samples
and
from
the
amended
ones
(Fig.
3).
In
the
upper
horizons
(Ap
and
AB),
the
amount
of
Al
was
greater
at
a
rate
of
40t
gypsum
ha
-1
;
in
the
Bt1,
the
opposite
was
true.
The
application
of
2286
VIZCAYNO
ET
AL.
lime
+
gypsum
to
the
Ap
and
AB
horizons
resulted
in
large
amounts
of
extracted
Al
relative
to
the
unamended
samples
and
also
to
those
that
were
supplied
with
gypsum
alone.
In
all
horizons,
raising
the
amount
of
gypsum
added
markedly
increased
the
amount
of
oxalate-Al
extracted
(Fig.
3).
The
addition
of
lime
+
gypsum
had
no
effect
on
the
Ap
horizon;
in
the
Bt1
horizon,
however,
the
amount
of
extracted
Al
was
appropriate
taking
into
account
that
gypsum
was
added
at
30
t
ha
-1
and
that
lime
had
no
effect
on
it.
The
.2
mm
fraction
in
the
different
profile
horizons
was
composed
of
quartz,
phyllosilicates,
and
hematite
(Table
3).
The
quartz
content
decreased
whereas
that
of
phyllosilicates
increased
with
increasing
depth.
Hematite
was
present
in
a
high
proportion
in
the
Ap
horizon;
on
the
other
hand,
goethite
was
present
in
small
amounts
in
all
samples
(somewhat
greater
in
the
Bt
horizons).
Traces
of
feldspars
and
gibbsite
were
also
detected.
The
clay
fraction
(
.
2
ilm,
Table
3)
consisted
largely
of
kaolinite,
which
increased
with
depth.
Illite
and
vermiculite
were
present
in
proportions
of
16
and
17%
in
the
Ap
horizon,
their
contents
being
smaller
(11
and
6%)
in
the
Bt
horizons.
The
gypsum
treatment
on
the
Ap
horizon
resulted
in
weaker
hematite
X-ray
diffraction
peaks
(Fig.
4);
this
effect
was
not
seen
with
the
lime
+
gypsum
amendment.
In
the
Bt1
horizon,
both
treatments
(gypsum
and
lime
+
gypsum)
decreased
the
kaolinite
content
(Fig.
5).
It
is
important
to
note
that
the
high
amount
of
Al
oxalate
obtained
for
the
Ap
horizon
(unamended
sample),
which
also
contained
the
largest
amount
of
sorbed
Al,
is
not
related
to
the
phyllosilicate
or
hematite
content.
Table
3.
Semi-quantitative
Mineralogical
Composition
(Relative
%
Between
Samples)
of
the
Soil
Profile
Fraction
Hor
Q
F
G
H
Gb
Ph
K
I
V
<_2
mm
Ap
37
tr
2
20
tr
38
AB
29
tr
4
13
tr
52
Bt1
19
tr
6
9
tr
64
Bt2
12
tr
6
12
tr
67
2
ilm
Ap
tr
tr
4
6
tr
86
53
16
17
AB
tr
tr
5 5
tr
88
58
20
10
Bt1
tr
tr
5
4
tr
88
71
11
6
Bt2
tr
tr
4
6
tr
87
73
12
2
Q
quartz,
F
feldspars,
G
goethite,
H
hematite,
Gb
gibbsite,
Ph
phyllosilicates,
K
kaolinite,
I
illite,
V
vermiculite,
tr
traces,
not
determined.
EXTRACTABLE
FORMS
OF
ALUMINUM
2287
In
all
horizons,
increasing
the
amount
of
gypsum
amendment
increased
the
amount
of
citrate-
extractable
Al
(Fig.
3).
The
addition
of
lime
+
gypsum
had
no
effect
(see
column
C5,
between
C1
and
C3).
Although
in
the
unamended
sample
treated
with
citrate,
the
vermiculite
peaks
were
absent
from
the
XRD
patterns,
as
a
result
of
the
collapse
at
10
A
caused
by
the
release
of
interlayered
Al,
no
relationship
between
the
vermiculite
content
and
the
difference
between
the
amount
of
Al
extracted
by
citrate
and
oxalate
was
found.
In
the
unamended
samples,
the
amount
of
dcb-extractable
Al
increased
with
increasing
depth
(Fig.
3)
and
seems
to
be
related
to
the
goethite
content,
as
determined
by
XRD.
Seed
nascence
and
crop
production
for
Raphanus
sativus
in
pots
to
which
gypsum
or
lime
+
gypsum
amendments
were
applied
(Table
4)
were
markedly
high
relative
to
the
unamended
pots.
C5
C3
0.251
0.269
CO
30
40
50
60
20
Cu
Ka
Figure
4.
X-ray
diffraction
patterns
of
the
whole
fraction
mm)
of
the
Ap
horizon.
CO
unamended
samples;
C3
samples
treated
with
40
t
gypsum
ha
-1
;
C5
samples
treated
with
17.5
t
lime
ha
-1
+30
t
gypsum
ha
-1
.
(d-values
in
nm).
0.1
9
2288
VIZCAYNO
ET
AL
0.358
0.256
0.170
0.71
C5
C3
CO
11111
1
1
[
1
I
'
I
10
20
30
40
50
60
70
20
Cu
Ka
Figure
5.
X-ray
diffraction
patterns
of
the
whole
fraction
(
.2
mm)
of
the
Bt1
horizon.
CO
unamended
samples;
C3
samples
treated
with
40
t
gypsum
ha
-1-
;
C5
samples
treated
with
17.5
t
lime
ha
-1-
+30
t
gypsum
ha
-1
.
(d-values
in
nm).
Table
4.
Effect
of
the
Application
of
Gypsum
and
Lime
+
Gypsum
Amendments
on
Raphanus
sativus
Growth
Treatment
in
Ap
Horizon
Seed
%
Root
Weight'
g
Leaf
Weight'
g
Control
35
4.24
8.20
20
t
gypsum
ha
-1
65
8.67
19.42
40
t
gypsum
ha
-1-
70
9.02
23.30
17.5
t
lime
ha
-1-
+30
t
gypsum
ha
-1-
80
9.70
26.80
a
Dry
per
pot.
EXTRACTABLE
FORMS
OF
ALUMINUM
2289
The
application
of
gypsum
or
lime
+
gypsum
lowered
the
level
of
exchangeable
aluminum
in
soil.
This
result,
however,
could
not
be
accounted
for
the
quantitative
levels
of
Al
in
the
outflow
solutions,
since
based
on
the
study
of
the
elements
obtained
from
the
treatments
and
leachates,
Al
is
released
in
relatively
small
amounts
from
the
soil.
In
our
opinion,
the
most
likely
mechanism
for
the
immobilization
of
Al
could
be
the
formation
of
a
solid
phase
according
to
the
observations
of
Pavan
et
al.
(7),
O'Brien
and
Sumner
(8)
and
Garcia-Gonzalez
et
al.
(9).
However,
our
results
contradict
those
of
Oates
and
Caldwell
(10),
who
found
that
a
substantial
amount
of
exchangeable
Al
can
be
removed
from
the
soil
if
large
amounts
of
gypsum
are
used
and
if
adequate
leaching
occurs,
possibly
because
they
used
very
short
subsoil
columns.
It
is
well
known
that
Si
is
leached
from
soil
after
gypsum
amendments.
According
to
Shainberg
et
al.
(1)
and
Sumner
(2),
this
occurs
because
of
the
decomposition
of
kaolinite.
In
this
work,
gypsum
or
lime
+
gypsum
treatments
cause
a
loss
of
Si
from
the
soil
columns,
and
also
a
decrease
in
the
characteristic
peaks
for
kaolinite
in
the
Bt1
horizon
was
observed.
Both
findings
support
this
hypothesis.
Exchangeable
Mg
in
the
soil
columns
was
removed
from
the
Ap
horizon
and
accumulated
in
the
AB
and
Bt1
horizons,
consistent
with
the
results
of
Shainberg
et
al.
(1),
who
suggested
that
Mg
may
be
removed
from
the
topsoil
and
accumulated
in
the
subsoil
before
it
is
completely
lost.
In
some
cases
(particularly
in
highly
sandy
soils),
heavy
gypsum
applications
(>5
t
ha
-1
)
have
an
adverse
effect
on
crop
growth,
owing
to
the
preferential
removal
of
magnesium
from
the
upper
part
of
the
profile
with
little
change
in
the
K
status
(11). The
sandy
clay
loam
texture
of
our
soil
probably
gave
rise
to
the
increased
Raphanus
sativus
yield
observed.
This
effect
was
also
found
by
the
addition
of
40
t
gypsum
ha
-1
.
The
loss
of
organic
C,
which
was
detected
only
after
gypsum
treatment,
is
consistent
with
the
results
of
Belkacem
and
Nys
(12),
who
attributed
it
to
the
competition
between
organic
dissolved
carbon
and
SO4
-
anions
for
positively
charged
exchange
sites.
The
gypsum
amendment
gives
rise,
in
the
Ap
horizon,
to
a
diminution
of
the
non-hydrolysable
C
and
a
increase
of
the
humic
acid
contents,
which
produced
a
greater
extracted
amount
of
Al
bounded
to
organic
matter
than
in
the
untreated
sample.
Lime
+
gypsum
caused
a
less
marked
decreased
in
unhydrolyzed
C
than
gypsum
and
results
in
a
extracted
proportion
of
Al
bound
to
organic
matter
similar
to
that
in
the
unamended
sample,
possibly
because
of
the
higher
pH
(5.9)
of
the
samples
treated
with
lime
+
gypsum
relative
to
those
with
gypsum
alone
(pH
4.5).
This
gypsum
amendment
causes
a
marked
depolymerization
of
non-hydrolysable
organic
compounds.
Also,
because
the
amount
of
organic
bound
Al
extracted
following
application
of
lime
+
gypsum
2290
VIZCAYNO
ET
AL.
(column
C5)
is
very
similar
to
that
extracted
from
the
unamended
sample,
the
resulting
depolymerized
compounds
can
be
assumed
to
contain
no
Al.
The
application
of
gypsum
amendment
on
the
Ap
horizon
provoked
a
large
decrease
in
the
hematite
content.
Also,
in
this
horizon,
based
on
the
similar
amounts
of
Al
extracted
with
citrate
and
dcb
in
the
unamended
sample,
can
be
assumed
that
in
the
hematite
lattice
no
isomorphic
substitutions
of
Fe
by
Al
exists.
In
the
unamended
and
gypsum
amendment
samples
the
content
of
sorbed-
Al
is
higher
than
the
exchangeable
and
organic
matter
bound
Al,
which
indicates
that
Al
is
present
mostly
as
polymeric
Al,
according
to
Soon
(3)
who
indicated
that
extractions
with
KC1
(exchangeable
Al)
and
CuC1
2
(organic
matter
bound
Al)
provide
an
estimation
of
presumably
monomeric
Al
and
the
subsequent
extraction
of
Al
by
NH
4
acetate
at
pH
4
(sorbed
Al)
probably
operates
through
depolymerization
of
polynuclear
hydroxy-Al
sorbed
on
clay
or
on
organic
matter
surfaces.
The
addition
of
lime
+
gypsum
raised
the
pH
and
hence
resulted
in
the
conversion
of
monomeric
Al
into
polymeric
Al;
this
action
explains
why
the
exchangeable
and
organic
bound
Al
contents
are
low
and
the
sorbed
Al
contents
especially
high.
Although
Oates
and
Caldwell
(10)
found
no
plant
response
in
terms
of
height
or
weight
to
gypsum
amendments
and
leaching,
we
obtained
significantly
increased
productivity
as
regards
seed
nascence
and
root
and
leaf
dry
weight
from
the
gypsum
or
lime
+
gypsum
treatments.
This
result
is
consistent
with
the
results
of
Noble
et
al.
(13),
who
achieved
improved
conditions
for
root
development
by
increasing
the
Ca/Al
ratio,
either
through
the
supply
of
additional
Ca,
the
reduction
of
Al
activity
or
both.
CONCLUSIONS
The
amount
of
Al,
Na,
K,
and
Si
leached
following
the
addition
of
gypsum
and
lime
+
gypsum
amendments
are
very
small.
The
addition
of
gypsum
causes
depolymerization
of
non-hydrolysable
C,
which
facilitates
the
extraction
of
Al
bound
to
organic
compounds.
The
application
of
gypsum
or
lime
+
gypsum
lowers
exchangeable
Al
levels;
also,
the
low
proportion
of
Al
in
the
outflow
solutions
suggests
its
immobilization
as
a
solid
phase.
Except
for
exchangeable
Al,
the
gypsum
amendment
increases
the
proportion
of
all
Al
extracted
forms
(bound
to
organic
matter,
sorbed,
oxalate
and
citrate)
relative
to
the
unamended
samples.
The
amount
of
Al
extracted
increases
as
that
of
gypsum
added
does.
Gypsum
or
lime
+
gypsum
amendments
increase
soil
productivity.
EXTRACTABLE
FORMS
OF
ALUMINUM
2291
ACKNOWLEDGMENTS
The
authors
are
grateful
to
Professors
Drozd
and
Weber
for
their
help
in
studying
the
organic
matter.
This
research
was
supported
by
Spain's
DGICYT
under
Project
PB94-39.
REFERENCES
1.
Shainberg,
Y.;
Sumner,
M.E.;
Miller,
W.P.;
Farina,
M.P.W.;
Pavan,
M.A.;
Fey,
M.V.
Use
of
Gypsum
on
Soils:
A
Review.
Adv.
Agron.
1989,
9,1-111.
2.
Sumner,
M.E.
Gypsum
and
Acid
Soils:
The
world
Scene.
Adv.
Agron.
1993,
51,
1
—32.
3.
Soon,
Y.K.
Fractionation
of
Extractable
Aluminum
in
Acid
Soils:
A
Review
and
a
Proposed
Procedure.
Commun.
Soil
Sci.
Plant
Anal.
1993,
24,
1683
—1708.
4.
Mehra,
O.P.;
Jackson,
M.L.
Iron
Oxide
Removal
from
Soils
and
Clays
by
a
Dithionite-citrate
System
Buffered
with
Sodium
Bicarbonate:
Proceedings
7th
National
Conference.
Clays
Clay
Minerals
1960,
9,
317-337.
5.
Schultz,
L.G.
Quantitative
Interpretation
of
Mineralogical
Composition
from
X-ray
and
Chemical
Data
for
the
Pierre
Shale;
U.S.
Geol.
Surv.
Prof.
Paper
391-C,
C1—C31
U.S.
Government
Printing
Office:
Washington,
DC,
1964.
6.
Tiurin,
I.V.
Vers
Une
Mithode
d'Analyse
Pour
l'Etude
Comparative
des
Constituants
de
l'Humus
du
Sol;
Travaux
de
l'Institut
des
sols
Dokutchaiev:
Moscow,
Russia,
1951;
Vol.
38,
32.
7.
Pavan,
M.A.;
Bingham,
RT.;
Pratt,
P.F.
Redistribution
of
Exchangeable
Calcium,
Magnesium,
and
Aluminum
Following
Lime
or
Gypsum
Applications
to
a
Brazilian
Oxisol.
Soil
Sci.
Soc.
Am.
J.
1984,
48,
33-38.
8.
O'Brien,
L.0.;
Sumner,
M.E.
Effects
of
Phosphogypsum
on
Leachate
and
Soil
Chemical
Composition.
Commun.
Soil
Sci.
Plant
Anal.
1988,
9,
1319-1329.
9.
Garcia-Gonzalez,
M.T.;
Vizcayno,
C.;
Cortabitarte,
J.
Influence
of
Kaolinite
and
Sulfate
on
the
Formation
of
Hydroxy-aluminum
Compounds.
Clays
Clay
Minerals
2000,
48,
85-94.
10.
Oates,
K.M.;
Caldwell,
A.G.
Use
of
By-product
Gypsum
to
Alleviate
Soil
Acidity.
Soil
Sci.
Soc.
Am.
J.
1985,
49,
915-918.
11.
Syed-Omar,
S.R.;
Sumner,
M.E.
Effect
of
Gypsum
on
Soil
Potassium
and
Magnesium
Status
and
Growth
of
Alfalfa.
Commun.
Soil
Sci.
Plant
Anal.
1991,
22,
2017-2028.
2292
VIZCAYNO
ET
AL.
12.
Belkacem,
S.;
Nys,
E.
Consequences
of
Liming
and
Gypsum
Top-dressing
on
Nitrogen
and
Carbon
Dynamics
in
Acid
Forest
Soils
with
Different
Humus
Forms.
Plant
Soil
1995,
173,
79-88.
13.
Noble,
A.D.;
Fey,
N.M.V.;
Sumner,
M.E.
Calcium
Aluminum
Balance
and
the
Growth
of
Soybean
Roots
in
Nutrient
Solutions.
Soil
Sci.
Soc.
Am.
J.
1988,
52,
1651-1656.