Vol.2, No.3, 334-340 (2011)
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
Agricultural Scienc es
Effects of tillage, fallow and burning on selected
properties and fertility status of Andosols in the Mounts
Bambouto, W est Cameroon
Paul Tematio1*, Ertine Isabelle Tsafack2, Lucas Kengni2
1Department of Earth Science, University of Dschang, Dschang, Cameroon; *Corresponding Author: paultematio@yahoo.fr
2Department of Earth Science, University of Dschang, Dschang, Cameroon.
Received 28 January 2011; revised 23 May 2011; accepted 7 July 2011.
To assess the imp act of land u se on the Andosol
fertility, changes in chemical and physical pro-
perties affecting soil quality were monitored on
Andosols from Mount Bambouto submitted to
four different land uses and management sys-
tems: natural cover, tillage, burning and fallow.
In comparison with the natural cover, tillage
reduces Andosol OC (6.5% to 4.8%), total N
(4.51‰ to 2.95‰), CEC (22.0 to 20.9 cmol·kg–1)
and the abundance of soil macro-aggregates
expressed by the water stable aggregates (WSA)
varies from 53.8% to 12.0%; and increases the
bulk density (0.69 to 1.09 g·cm–3) and the sum of
exchangeable cations (3.58 to 4.84 cmol·kg–1).
Burning also reduces Andosol OC (6.5% to
0.8%), total N (4.51‰ to 0.95‰) and CEC (22.0 to
10.2 cmol·kg–1), but increases soil pH (4.62 to
6.54), the sum of exchangeable cations (3.58 to
5.74 cmol·kg–1) and the abundance of soil
macro-aggregates (WSA: 38.2% to 57.0%). In
comparison with tillage, fallow increases An-
dosol OC (4.8% to 6.5%), total N (2.95‰ to
5.04‰), CEC (18.0 to 21.6 cmol·kg–1), the sum of
exchangeable cations (3.58 to 5.05 cmol·kg–1)
and the abundance of soil macro-aggregates
(WSA: 12.0% to 48.8%). Globally, the tillage man-
agement deteriorates Andosol chemical and
physical properties affecting fertility, whereas
the fallow management restores them. The
burning management also improves some An-
dosol chemical and physical properties affect-
ing quality, but it won’t last long.
Keywords: Andosols; Land Use Management
Systems; Soil Physic-Chemical Properties; Soil
Soil quality is fundamental for sustainable agriculture
development [1]. The land use and management systems
strongly influence soil quality expressed by changes in
soil chemical and physical properties (organic matter
content, CEC, sum of exchangeable cations, acidity, bulk
density, aggregates stability, etc.). Thus, improper land
use and management systems reduce soil fertility and the
subsequent food security [2]. Many studies on soil fertil-
ity have focused mainly on nutrients budget and bal-
ances [3,4] without emphasis on changes in soil chemi-
cal and physical properties affecting soil quality over
In Mount Bambouto, a volcanic mountain of the West
Cameroon Highlands where Andosols are widespread [5]
(Figure 1), strong human pressures on lands expressed
by the tillage and burning management systems have
affected the agro-ecosystems over the past 30 years [6].
One of the consequences is the overexploitation of soil
resources with subsequent crop yields decrease. Consid-
ering the precarious conditions of Andosols character-
ized by a rapid degradation of the majority of their
chemical and physical properties when farming, new
strategies for sustainable management of Andosols in
this area have to be found urgently. Therefore, it might
be useful to identify the land use and management sys-
tems impacts on Andosol fertility in Mount Bambouto.
The main objective of this study is to quantify changes
in chemical and physical properties of the Andosols from
Mount Bambouto submitted to tillage, burning or fallow
management systems in order to compare the effects of
these land uses and management systems on Andosol
quality changes. This would contribute to propose stan-
dard systems that safeguard Andosol quality.
This study was carried out in Mount Bambouto, one
P. Tematio et al. / Agricultural Science 2 (2011) 334-340
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
Figure 1. Location of the studied plots in the soil distribution
map of Mount Bambouto (after Tematio et al., 2004).
of the major volcanoes in the Cameroon Volcanic Line
that crosses the western part of the Cameroon territory.
In this mountain, a recent soils survey [5] points out that
Andosols are widespread above the altitude 2000 m
(Figure 1).
They are shallow weathered pedons, either with A and
BC horizons when developed on crests and steep slopes,
or A, B and BC horizons when developed on foot-slopes.
The surface horizon A is the main agricultural soil hori-
zon supporting crops farming. It corresponds to a thick
(up to 60 cm) and dark grey to dark brown (10YR3/2 -
10YR3/3) loamy soil with fine to coarse crumbly struc-
ture. These Andosols in Mount Bambouto are mainly
devoted to Irish potato and cabbage farming.
In this area, 17 plots were selected with respect to the
farming crops (Irish potatoes), the slopes gradient (slightly
undulated landscape), the landscape position (foot-slopes),
the type of land use and management system applied and
its duration. They are distributed as follow: 3 plots under
the natural cover named NT, 2 plots under the short-term
(5 years) tillage (T1), 4 plots under the long-term (10
years) tillage (T2), 2 plots under the short-term (5 years)
burning (B1), 2 plots under the long-term (10 years)
burning (B2), 2 plots under the short-term (5 years) fal-
low (F1) and 2 plots under the long-term (10 years) fal-
low (F2). In this area, the most significant variations in
chemical and physical properties induced by the different
land use and management systems occurred within the
first 40 cm of the surface horizon A. That is why in each
selected plot, soil samples for chemical analyses were
collected at 20 cm depth, mixed, air dried, crushed and 2
mm sieved. Undisturbed soil samples were also collected
at the same depth for bulk density and aggregates stability
Chemical analyses include the soil organic carbon
(OC), the total nitrogen (N), the available phosphorus
(P), the exchangeable cations; the cations exchange ca-
pacity (CEC) and the soil pH. OC was extracted by oxi-
dation with potassium dichromate in strongly acid solu-
tion and determined using a TOC-5000A analyzer. The
total N was determined by Kjeldahl method, the avail-
able P by Bray II method and the exchangeable cations
extracted by NH4OAc buffered at pH 7 and determined
by atomic absorption spectrophotometer. The CEC at pH
7 was determined using ammonium acetate method. The
soil pH was determined in a 1:2.5 soil suspension with
deionised water.
Physical analyses refer to the bulk density (da), the
particle size distribution and the soil aggregate stability.
da was obtained using the cylinder of Koppeki method
[7]. With regard to the particle size distribution, sand
fraction was separated by wet-sieving with 63 µm sieve,
oven dried at 105˚C and weighed. Silts and clay frac-
tions were determined by laser diffraction after destruc-
tion of organic matter with hydrogen peroxide, followed
by the particle dispersal in sodium hexametaphosphate
solution. The soil aggregate stability was determined
according to Le Bissonnais method [8] which combines
3 disruptive tests: slow wetting, fast wetting and me-
chanical breakdown by shaking after pre-wetting tests.
After each test, residual aggregates were collected and
sieved using a column of six sieves: 2000, 1000, 500,
200, 100, and 50 μm. The proportion of each fraction
size of stable aggregates was calculated.
Data analyses refer to the sum of exchangeable cations
(S), the cations equilibrium (Ca/Mg/K), Al3+ toxicity (m)
and the soil aggregate stability calculation. S is obtained
by summing up the exchangeable cations. The cations
equilibrium noted (Ca/Mg/K) is the relative abundance
of Ca2+, Mg2+ and K+ in soil qualifying the competition
between the above cations during plant nutrition.
. (1)
represents the concentration of free Al3+ in the soil solu-
tion. The soil aggregate stability is expressed by the wa-
ter stable aggregates (WSA), the geometric mean diame-
ter (GMD) and the mean weight diameter (MWD) of the
soil aggregates above 0.5 mm size. They correspond to:
. (2)
. (3)
P. Tematio et al . / Agricultural Science 2 (2011) 334-340
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Table 1. Mean values of the physical and chemical soil characteristics in the study plots.
Soil organic matter Exchangeable cations Exchange-
able acidity
Particles size
distribution (%)
plots OC (%) N (‰(mg·kg–1) (cmol·kg–1)
e Coarse sand
) P Ca2+ Mg2+ K
+ Na+ S
Al3+ m (%)pH
(g·cm–3) clay Fin
silt silt (76/18/6)
tilled NT 6.5 ± 1. 1.0 1.68 0..58 ±
22.0 ±29 04 4.51 ± 1.1 7.0 ± 94 0.76 0.03 33.1 0.31 5.9 ±
1.7 4.62 ±
0.2 0.69 .0 52.0 17.0 2.78/17/5
T1 3.±
0.7 18.0
± 1.9 31.0 4.
0.5 0.93
5.7 ± 0.2 4.15 ± 0.6 22.2 ± 1.6 1.76 1.05 0.75 0.02 58 0.2 7.0 ± 42 ±36.0 47.0 13.0 4.054/39/7
T2 4.8 ± 0.5 2.95 ± 0.7 11.7 ± 1.9 3.08 1.48 1.03 0.02 4.84 ±
1.1 20.9
2.7 0.19 5.5 ±
0.4 4.53 ±
0.2 1.09 31.0 53.0 13.0 3.073/20/7
B1 0.8 ± 0.0 0.95 ± 0.0 18.7 ± 0.0 6.27 4.43 3.98 0.03 5.74 ±
0.0 10.2
± 0.0 0.00 0.0 ±
0.0 6.54 ±
0.0 0.77 20.0 34.0 34.0 12.058/25/17
B2 1.5 ± 0.0 1.96 ± 0.0 43.6 ± 0.0 5.87 3.05 .3.6 0.06 3.94 ±
0.0 11.4 ±
0.0 0.01 0.1 ±
0.0 6.18 ±
0.0 0.79 14.0 49.0 29.0 2.041/51/8
F1 6.5 ± 0.2 5.04 ± 0.6 10.8 ± 0.6 2.72 1.22 0.95 0.02 5.05 ±
1.1 20.6
± 1.0 0.27 5.1 ±
3.1 4.64 ±
0.1 1.14 25.0 45.0 28.0 2.078/17/5
F2 5.5 ± 0.3 1.87 ±
0.3 15.9 ± 0.8 1.67 1.06 1.01 0.01 4.39 ±
0.0 21.6
3.2 0.31 5.7 ±
1.1 4.47 ±
0.00 1.09 31.0 50.0 16.0 3.063/33/4
Openly accessible at
WD xw
. 4
here n is the number of aggregate size ranges above
0.5 mm, wi is the weight of aggregates in a size class of
average diameter xi, and w0 is the t
arbon (O C), Total Nitrogen (N)
study plots and
. Caange Capacity (CEC),
cle io
The CEC content is relatively high in the study plots and
0 cmol·kg) and T2 (20.7 cmol·kg), and se-
but innd F2
() 3.1.2 tions
han Exch
geabEx Catns and Acidity
otal weight of aggre-
gates placed on 5 mm sieve for analysis.
The mean values of the soil chemical and physical
properties in each series of plots under the same land use
and management system were obtained using M.S. EX-
CEL software.
3.1. Soil Chemical Properties
3.1.1. Organic C
and Available Phosphorous (P)
The soil OC content is high in the
varies from 4.8% to 6.5%, except in B1 (0.8%) and B
(1.5%) (Table 1). It decreeses slightly from NT (6.5%) t
(5.7%) and T2 (4.8%), and abruptly in B1 (0.8%) and
B2 (1.5%). Inversely, it increases in F1 (6.5%) and F2
(5.5%) compared to T1 and T2. The total N content fol-
lows the same trend like the soil OC content and varies
from 0.95‰ to 5.04‰. It thus decreases slightly from NT
(4.51‰) to T1 (4.15‰) and T2 (2.96‰), and abruptly in
B1 (0.95‰) and B2 (1.96‰), and increases significantly
in F1 (5.04‰), even remains low in F2 (1.87‰). The
available P content varies from 7.0 to 43.6 mg·kg–1 in the
study plots. Its lowest value is in NT (7.0mg.kg-1). It
increases in T1 (22.2 mg·kg–1), T2 (11.7 mg·kg–1), B1
(18.7 mg·kg–1) and B2 (43.6 mg·kg–1), but decreases in
F1 (10.8 mg·kg–1) and F2 (15.9 mg·kg–1) relative to T1
and T2.
varies from 10.2 to 22.0 cmol·kg–1 (Ta ble 1). The high-
est value is in NT (22.0 cmol·kg–1). It decreases slightly
in T1 (18.–1–1
verely in B1 (10.2 cmol·kg–1) and B2 (11.4 cmo
creases slightly in F1 (20.6 cmol·kg–1) a
(21.6 cmol·kg–1) with respects to T1 and T2. The sum of
exchangeable cations (S) is very low in the study soils
(3.6 to 5.7 cmol·kg–1). It increases slightly from NT (3.6
cmol·kg–1) to T2 (4.9 cmol·kg–1), B1 (5.7 cmol·kg–1), B2
(3.9 cmol·kg–1), F1 (5.1 cmol·kg–1) and F2 (4.3
cmol·kg–1), and remain unchanged in T1 (3.6 cmol·kg–1).
It highest content is in B1. The most abundant ex-
changeable cation is Ca2+ (1.60 to 3.92 cmol·kg–1), fol-
lowed by Mg2+ (0.61 to 2.00 cmol·kg–1), K+ (0.15 to 0.99
cmol·kg–1) and Na+ (0.03 to 0.09 cmol·kg–1). The cations
equilibrium is close to the optimal equilibrium (76/18/6)
in NT (78/17/5), T2 (73/20/7) and F1 (78/17/5), and
highly unbalanced in T1 (54/39/7), B1 (58/25/17), B2
(41/51/8) and F2 (63/33/4) with respect to a Ca defi-
ciency. The exchangeable Al3+ content varies from 0.00
to 0.28 cmol·kg–1. Consequently, the aluminium toxicity
is relatively low (m: 0.0% to 7.0%). Nevertheless, the
study soils are strongly acids (pH 4.42 to 4.64), except
for B1 and B2 with weak acid soils (pH 6.54 and 6.18
respectively). This acidity increases slightly from NT
(pH 4.62) to T1 (pH 4.42) and T2 (pH 4.53), but de-
creases abruptly in B1 (pH 6.54) and B2 (pH 6.18) and
slightly in F1 (pH 4.64) and F2 (pH 4.47) relative to T1
and T2.
P. Tematio et al . / Agricultural Science 2 (2011) 334-340
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
r sta
Fast wetting test Stirring after wetting test
Ta b le 2. Soil aggregates stability in the study plots (WSA: wateble aggregates; GMD: geometric mean diameter; MWD: mean
weight diameter).
Slow wetting test Test
Study plots WSA (%)GMD (mm) MWD (mm)WSA (%)GMD (mm)MWD (mm)WSA (%) GMD (mm)MWD (mm)
Not tilled NT 53.8 1.76 2.69 38.9 1.55 1.95 38.2 1.47 1.91
T1 48.4 1.62 2.42 37.9 1.44 1.90 34.5 1.26 1.72
Tilled T2 29.4 1.30 1.47 12.0 1.18 0.06 15.8 0.94 0.79
53.3 2.66 53.3 2.67 46.B1
Burn B2
1.70 1.69 7 1.55 2.34
57.0 1.72 2.85 51.4 1.70 2.57 52.2 1.64 2.61
F1 40.1 1.55 2.00 27.5 1.28 1.38 48.2 1.67 2.41
Fallow F2 48.8 1.63 2.44 42.5 1.53 2.13 29.6 1.28 1.48
3.2il Phal Prties
3.2.1. Bulk Density (da) and Particle Size
.69 to 1.14 g·cm–3.
The lowest value is in NT (0.69 g·cm–3). It increases
–3), F1
(1.14 (1.09 g·cm), and lesser in B1
n Tab le 2 (29.4%, 12.0% and 15.8%) and the
highest in B2 (57.0%, 51.4% and 52.2%), respectively
ting and the stirring
r pre-wetting (0.94 - 1.67 mm)
the st afterwettin9 - mm) tests. It
alwayrease NT - 2.6) to T72
- 2.42), T2 - 1.4), F1 - 2.m)
and F2 (1.48 - 2.44 mm), but increases in B1 (2.34 - 2.67
mm). The lowest MWD values
- 48.2%) and F2 (29.6% - 48.8%); but increases
In the Andosols from Mount Bambouto, the tillage
sults in a significant reduction of
the so
. Soysicrope
The bulk density (da) varies from 0
significantly in T1 (0.93 g·cm–3), T2 (1.09 g·cm
g·cm–3) and F2–3
.77 g·cm–3) and B2 (0.79 g·cm–3). The silt (60 to 78%)
and clay (14 to 36%) fractions are dominant. The clay
fraction increases in T1 (36%) and T2 (31%), and de-
creases in B1 (20%) and B2 (14%) relative to NT (29%).
It also decreases in F1 (25%) and F2 (31%) compared to
T1 and T2. The highest fine silt content is in NT (53%).
It decreases in T1 (47%), B1 (34%), B2 (49%), F1 (45%)
and F2 (50%) and remains unchanged in T2 (53%). The
coarse silt abundance also decreases from NT (17%) to
T1 (13%) and T2 (13%), but increases in B1 (34%) and
B2 (29%). It also increases in F1 (28%) and F2 (16%)
compared to T1 and T2. The sand fraction is the less
abundant (2% to 12%) with the highest value in B1
3.2.2. Aggregate Stability
The soil aggregate stability parameters are dis-
played i
after the slow wetting, the fast wet
ter pre-wetting tests.
The geometric mean diameter (GMD) of the soil
macro-aggregates decreases progressively after the slow
wetting (1.30 - 1.76 mm), the fast wetting (1.48 - 1.70
mm) and the stirring afte
sts. It decreases from NT (1.47 - 1.76 mm) to T1 (1.26 -
1.62 mm), T2 (0.94 - 1.30 mm), B1 (1.55 - 1.70 mm), B2
(1.64 - 1.72 mm), F1 (1.28 - 1.67 mm) and F2 (1.28 -
1.63 mm) whatever the test. The lowest GMD values are
in T2 (1.30 mm, 1.18 mm and 0.94 mm, respectively
after the slow wetting, the fast wetting and the stirring
after pre-wetting tests).
The mean weight diameter (MWD) of the soil macro-
aggregates also decreases severely after the slow wetting
(1.47 - 2.69 mm), the fast wetting (0.60 - 2.67 mm) and
mm) and B2 (2.57 - 2.85
irring pre-g (0.72.61
s decs from(1.919 mm1 (1.
mm(0.607 mm (1.3841 m
these soil macro-aggregates remain in T2 (1.47 mm,
0.60 mm and 0.79 mm after the slow wetting, the fast
wetting and the stirring after pre-wetting tests respec-
The water stable aggregates (WSA) abundance in the
study soils remains relatively high after the slow wetting
test, and vary from 29.4% to 57.0%. It decreases sig-
nificantly after the fast wetting (12.0% to 53.3%) and the
stirring after pre-wetting (15.8% to 52.2%) tests regard-
less of the land use and management systems. It de-
creases in T1 (34.5% - 48.4%), T2 (12.0% - 29.4%), F1
ightly in B1 (46.7% - 53.3%) and B2 (51.4% - 57.0%)
compared to NT (38.2% - 53.8%). The lowest WSA
abundance is in T2
Variations in most of the soil chemical and physical
properties are the key for understanding the impact of
land use and management systems on soil quality.
4.1. Changes in Soil Chemical Properties
management system re
il organic matter expressed by the soil OC (6.5% to
4.8%) and the total N (4.51% to 2.96‰) contents, giving
a reduction ratio of 26.1% and 34.4% respectively .
Similar reduction has been reported [9,10] with the
OC losses ranging from 15% to 40% within 2 - 12 yea
of tillage [11, 12]. Such reduction is commonly attribut
the microbial oxidation of the organic compounds
previously protected in the soil aggregates which where
destroyed by cultivation [13,14]. The burning manage-
ment system also reduces severely the soil organic matter
content by calcinations (OC: 6.5% to 0.8%, N: 4.51‰ to
0.95‰) giving a reduction ratio of 87.7% and 78.9%
respectively. Generally, reduction in the soil organic
P. Tematio et al . / Agricultural Science 2 (2011) 334-340
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
three land
en after 10years
ing to moderate rainfalls is
matter content influences negatively the fertility of An-
dosols, since it is known to play a central role in the ex-
changeable cations retention [15]. This reduction could
also increase the soil erodibility, causing an offsite
transport of the soil nutrients and the subsequent soil
fertility decline. Conversely, the fallow management
system improves the soil organic matter content relative
to the tillage management system (OC: 4.8% to 6.5%, N:
2.96‰ to 5.04‰) with an increasing ratio of 26.1% and
41.3% respectively. This increase in the soil organic
matter content with fallow may be consistent with addi-
tional supply of the organic residues which act as com-
post with time [16]. These particulate organic matters are
protected physically in soil aggregates [17].
In the Andosols from Mount Bambouto, the tillage and
burning management systems also lead to a net loss of the
CEC content (22.0 to 18.0 and 10.2 cmol·kg–1) with a
reduction ratio of 18.2% and 53.6% respectively, giving
rise to the soil fertility decline [18], whereas the fallow
management system restores it relative to the tillage
management system (18.0 to 21.6 cmol·kg–1) with an
increasing ratio of 16.7%. Inversely, the above
e and management systems are marked by a slight
increase of the sum of the exchangeable cations relative
to the natural cover (3.6 to 4.9 cmol·kg–1, 5.7 and 5.1
cmol·kg–1) with and increasing ratio of 26.5%, 36.8% and
29.4% respectively. In the tillage management system,
this may be due to an input of fertilizers during land
preparation. In the fallow management system, it sug-
gests that this unmanaged period can restore the soil
nutrients exported by the harvest of the plant biomass. In
the burning management system, it may be consistent
with the release of the base cations during soil calcination
[19] as indicated by the net increase in the soil pH values
in B1 (6.54) and B2 (6.18). Thus, the burning manage-
ment system improves the soil fertility through accumu-
lation of the exchangeable cations. But it is well known
that this improvement lasts only for a short period and
that the water erosion and the subsequent soil nutrients
leaching leads to soil impoverishment [19]. The soil
acidity also increases in the tillage management system
compared to the natural cover (pH 4.62 to 4.42), inducing
the decrease in the agricultural productivity [20]. Even 10
years of the fallow management system practice (F2 plots)
is not enough to improve this strong acidity induced by
the tillage management system. Always in the Andosols
from Mount Bambouto, the long-term tillage (T2 plots)
and the fallow management systems have brought the
cations equilibrium close to the optimal equilibrium (T2:
73/20/7, F1: 78/17/5 and F2: 63/33/4) and consequently
improve Andosol fertility. Inversely, the short-term till-
age (T1 plots) and the burning management systems
provoke the cations imbalance (T1: 54/39/7, B1: 58/25/17
and B2: 41/51/8) with a significant Ca2+ deficiency. This
Ca2+ deficiency may induce a severe antagonism between
the cations during the plants nutrition.
4.2. Changes in Soil Physical Properties
The soil compaction (36.7%) induced by the tillage
management system and expressed by the soil bulk den-
sity increase (0.69 to 1.09 g·cm–3) has significant effect
on soil physical properties. It reduces infiltration and
percolation of water, and thus favours the surface runoff
and land degradation by soil erosion. Ev
of the fallow management system practice, these s
seem to have not recovered from the tillage managem
stem induced compaction.
The water stable aggregates (WSA: 12.0% - 53.3% and
15.8% - 52.2%) abundance, the geometric mean diameter
(GMD: 1.18 - 1.70 mm and 0.94 - 1.67 mm) and the mean
weight diameter (MWD: 0.60 - 2.57 mm and 0.79 - 2.61
mm) values reveal that the fast wetting and the stirring
after pre-wetting tests representing moderate to violent
storms highly disrupt the Andosol macro-aggregates. The
slow wetting test correspond
ast disruptive (WSA: 29.4% - 57.0%; GMD: 1.30 - 1.76
mm; MWD: 1.47 - 2.85 mm). Globally, the Andosols
from Mount Bambouto have low to moderate resistance
to water erosion. As the land use and management system
is concerned, the tillage management system lead to an
important destruction of the Andosol macro-aggregates
(WSA: 12.0% - 48.4%; GMD: 0.94 - 1.62 mm and MWD:
0.60 - 2.42 mm), whereas the burning management sys-
tem regenerates them ((WSA: 46.7% - 57.0%; GMD: 1.55
- 1.72 mm and MWD: 2.34 - 2.85 mm). The fallow man-
agement system also regenerates the Andosol macro-
aggregates after the tillage management system practice
(WSA: 27.5% - 48.8%; GMD: 1.28 - 1.67 mm and MWD:
1.38 - 2.44 mm). The destruction of the Andosol macro-
aggregates by the tillage management system with it
subsequent increasing clay fraction (36%) may be con-
sistent with the mechanical breakdown of the soil ag-
gregates by ploughing. The regeneration of the Andosol
macro-aggregates with the burning management system
practice may be related to Al3+ activity in the soil solution.
In fact, above pH 5.5, Al3+ precipitates in soil as hy-
droxides and can act as links between mineral particles,
generating soil aggregates. Under the fallow management
system, the regeneration of the Andosol macro-aggre-
gates may be associated to the formation of the organo-
metal and oxides-humus complexes with organic acids
acting as binding agent [21]. The increase in the Andosol
macro-aggregates abundance in both cases and the rela-
tively low bulk density indicate well-structured soils with
good pore connectivity.
P. Tematio et al . / Agricultural Science 2 (2011) 334-340
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
exchangeable cations and t
the optimal equilibrium after
are not enough to restore ef-
rovement lasts only for a
The tillage management system is a significant driver
of the Andosol fertility decline. It reduces significantly
the soil organic matter and the CEC content, increases
soil acidity and compaction, and destroys the Andosol
macro-aggregates; the chemical and physical properties
that affect negatively the Andosol quality. The relative
increase of the sum of thehe
cations equilibrium close to
10 years of tillage practice
iently the Andosol fertility.
The burning management system has mitigated influ-
ences on Andosols quality. The severe reduction of the
soil organic matter and the CEC content, and the cations
equilibrium imbalance in the burning management sys-
tem affect negatively the Andosol quality. Inversely, the
net increase of the sum of the exchangeable cations and
the soil pH above 6, and the fairly high soil macro-ag-
gregates abundance contribute to improve significantly
the Andosol quality. But this imp
ort period because the water erosion and it subsequent
nutrients leaching leads to the soil impoverishment.
The fallow management system globally improves
significantly the Andosol quality. It is sustainable in term
of the soil organic matter, the CEC and the sum of the
exchangeable cations increase, and the soil macro-ag-
gregates regeneration after the tillage management sys-
tem practice. But, even 10 years of the fallow manage-
ment system is not enough to regenerate efficiently the
soil macro-aggregates and improve the soil acidity.
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