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\begin{document}
\title{DYNAMICS IN PHYSICOCHEMICAL PROPERTIES OF SOILS UNDER OIL PALM
PLANTATIONS OF DIFFERENT AGES}
\author[1]{Olufemi Osinuga}%
\affil[1]{Federal University of Agriculture Abeokuta}%
\vspace{-1em}
\date{\today}
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\selectlanguage{english}
\begin{abstract}
Removing forest cover for oil palm plantations has raised questions
about climate change problems and debates and their associated impacts.
The design of the pruned fronds of the trees does not make them ideal
for use as mulch cover on the entire farm, but they are heaped between
the plant rows. This research investigated the changes in the
physicochemical properties of soils under oil palm plantations of
different ages. Soil surface (0-20 cm) and subsurface (20-40 cm) samples
have been obtained from various ages of oil palm plantations (0-5, 5-10,
10-15 and, 15-20 years). Two distinct samples were taken on the same
farm, under alleys and heaped pruned fronds. Soil samples used as a
standard (control) were collected from adjacent forest land. Analyses of
particle size showed that the soils were sandy loam to sandy clay loam
texture soils. Bulk density was low and varied with age and depth. The
soils were moderate to slightly acidic pH, relatively low organic
carbon, total nitrogen, and available phosphorus contents. Based on the
standard ratings, exchangeable bases and cation exchangeable capacity
content were also low, while high percent base saturation was observed.
Research findings have shown that the soil properties of different ages
of oil palm plantations vary and should therefore be handled differently
based on of their characteristics. Accumulation of organic residue on
the floor of the plantations should be encouraged as this will help to
increase organic matter levels.%
\end{abstract}%
\sloppy
\textbf{1. INTRODUCTION}
Oil palm (\emph{Elaeis guinensis} ) is one of the plantation crops grown
in some tropical countries of the world especially Nigeria in addition
to cocoa, kola, teak, gmelina, rubber, and cashew as a result of
transformations in agriculture. It is cultivated mostly in the southern,
eastern, and western parts of the country. Recently, planted areas had
increased at a rapid pace, and the increase is significantly evident.
Oil palm was adopted and cultivated among the high-value perennial tree
crops by individual small-scale growers, private agencies, and
government agencies (state and federal). Global oil palm production is
approximately 272,055,131 tonnes from 18,917,400 hectares, with Asia
(84.1\%) taking the lead, followed by Africa (9\%) (FAO, 2020). It is a
major source of oils and fats for human food, livestock feed, and
manufacturing of several other domestic products, such as cosmetics,
soap, and detergents (Reiger, 2006).
The increase in oil palm demand has resulted in the conversion of
natural vegetation into oil palm plantations. The conversion of some
rainforests and the use of abandoned logged-off forests into oil palm
plantations is expected to have contributed significantly to nutrient
losses from both soil and vegetation (Brahene et al., 2016; Rozieta et
al., 2016). Deforestation and loss of habitat of critically endangered
species (Clay, 2004), a decrease in soil productivity, an increase in
soil erosion, and soil biodiversity loss (Comte et al., 2012; Savilaakso
et al., 2014), and a substantial increase in greenhouse gas emissions
are the detrimental effects of oil palm on the climate (Bates et al.,
2008; Hassan et al., 2011). Rising tillage intensity and the conversion
of the natural environment to agricultural land have contributed to a
decline in soil organic matter levels due to decreased organic carbon
inputs and decreased physical conservation of soil organic carbon
contents (Chibsa and Ta'a, 2009).
As a consequence of the combined effects of physical, chemical, and/or
biological processes operating at various intensities and on different
scales, the classification of soils depends on the degree of spatial
heterogeneity (Priyabrata et al., 2008). Research has shown that crop
age also leads to soil variability because nutrients are extracted from
the soil during harvest for grain, fiber, wood, and crop residues as the
crops grow older (Basiron, and Weng, 2004; Aweto and Enaruvbe, 2010). If
replenishment with inorganic and/or organic fertilizers is insufficient,
nutrient removal can result in a decrease in soil fertility (Okon et
al., 2017). There seems to be little or no knowledge as touching the
impact of oil palm plantations of different ages on soil
physico-chemical properties in the research region to date on various
studies on oil palm plantations in Nigeria. Therefore, it is of great
importance to assess the quality of soil nutrients in existing oil palm
plantations of various maturity ages and to analyze the variability
(differences) in the soil properties of these oil palm plantations.
\textbf{2. MATERIALS AND METHODS}
Oil palm plantations owned by the Federal University of Agriculture,
Abeokuta (FUNAAB), were selected with a reference (control) soil
adjacent to the plantations. FUNAAB is located next to Ogun-Oshun River
Basin Development Authority (OORBDA), along Alabata road,
Abeokuta-Ibadan expressway. It lies in a humid tropical lowland zone
with two separate seasons (wet and dry). The wet season runs between
March and October, and the dry season runs between November and
February. The annual rainfall is between 1000-1500 mm, the annual
temperature is between 26-32\textsuperscript{0}C, and the relative
humidity varies between 70-88\%. The University superimposes the
Basement Complex's pre-Cambrian metamorphic rocks with bed-rock
consisting mainly of granitic gneisses, horn-blended gneisses, bounded
biotite, quartzite, and quartz schists.
The oil palm plantations ranged from young ones aged around five years
to farms as old as twenty years at various maturity ages. Marking an
area of 30 m by 30 m was followed by sampling. The sampling of farms
commenced by establishing four age-based clusters of oil palm
plantations into which numerous farms were clustered. A total of twelve
parcels, with three parcels for each age group, were chosen as
replicates for sampling. Soil samples were obtained at depths of 0-20 cm
and 20-40 cm. There were 0-5, 5-10, 10-15, and 15-20 years for the
different plantation age groups considered. The sampled plots comprised
both alleys within the palm rows and pruned and heaped palm fronds.
Undisturbed soil samples were collected within the alleys and under
heaped trees for bulk density analysis using core samplers. Under the
prunings, especially under old heaps, sampling was conducted with care
because the top layer had to be separated from the decomposed material
sitting just above it. Soils from the sampled spots of various depths
from each plantation were put together to obtain a composite sample. A
sub-sample was taken, air dried, crushed, and sieved through a 2 mm
sieve for routine laboratory testing, and processed.
Using the hydrometer method (Gee and Or, 2002), particle size
composition was performed, bulk density was determined using the core
sample method. The pH was calculated electrometrically using the glass
electrode pH meter in soil-water suspension, soil organic carbon was
measured using the digestion method of wet oxidation (Walkley and Black,
1934) and total nitrogen by the digestion method of macro-Kjeldahl
(Bremmer and Mulvaney, 1982). The Bray-1 extractant was used to extract
available phosphorus (Bray and Kurtz, 1945), while the P in the extract
was determined by the vanado-molybdate blue method (Murphy and Riley,
1962). With 1.0 M KCl and titrated with NaOH, exchangeable acidity
(H\textsuperscript{+} and AI\textsuperscript{3+}) was extracted, and
with 1.0 M NH\textsubscript{4}OAC at pH 7, exchangeable bases were
extracted. The atomic absorption spectrophotometer was used to determine
Ca\textsuperscript{2+} and Mg\textsuperscript{2+}, while the flame
photometer read K\textsuperscript{+} and Na\textsuperscript{+}. Cation
Exchangeable Capability (CEC) was gotten by the summation of
exchangeable bases and total acidity (Chapman, 1965). The base
saturation was gotten as the ratio of exchangeable bases to CEC.
Data were analyzed using descriptive statistics to show the relationship
between the variables in the plantations. The mean was used to derive
the average distribution of the variables, the standard deviation shows
how the variables deviate from the mean.
\textbf{3. RESULTS}
The physical and chemical properties of the soils were depicted in
Tables 1 and 2. The particle size fractions varied significantly (p
\textless{}0.05) with the age of plantations, and also varied with
depths. The sand fractions which ranged between 698--778 g/kg were
higher in the oil palm plantations, while silt (50-80 g/kg) and clay
(172-232 g/kg) fractions were higher in the forest (uncultivated) soils.
Analyses of the particle size revealed that the soil texture was sandy
loam and sandy clay loam. Bulk density (BD) values ranged between
0.93-1.25 g/cm\textsuperscript{3} and increase with depth. Under both
alleys and heaps, the rise in bulk density with depth was noticed, and
this could be due to the increasing clay content with depth. In the 0-20
cm layer, soil bulk density levels are relatively lower than those in
the 20-40 cm layer.
The soil pH values ranged from moderate to slightly acidic except for
the reference soil which was neutral. The pH was higher in the forest
surface layer with a value of 7.13 (Table 1) and lowest at the oil palm
alley 15-20 years with a value of 5.74 (Table 2). Between the 0-20 and
20-40 cm layers, the results varied significantly. Inside the oil palm
alleys, the pH of the soil appears to be lower than that under heaped
fronds and fluctuates as the years of planting increase. Generally,
available P did show a significant difference across all the oil palm
plantations and soil depths at p \textless{}0.05. The average available
P in the topsoil was higher than in the subsoil. The highest value of
the uncultivated topsoil was 6.21 mg/kg, followed by 6.10 mg/kg for the
oil palm heaps 15-20 years (Table 1), with the lowest values being 4.43
mg/kg in the oil palm alley 5-10 years (Table 2).
The soil organic carbon (OC) content was moderate, ranging from 12.4
g/kg to 21.7 g/kg for 0-20 cm depth (Table 1) while at 20-40 cm depth,
it ranged from 11.6 g/kg to 20.4 g/kg (Table 2). The OC content of the
reference (uncultivated) site was significantly (p\textless{} 0.05)
higher than the cultivated sites. Among the oil palm plantations, the
15-20 years old under heaps has the highest OC content (17.8 g/kg),
while the 1-5 years have the lowest OC content (11.6 g/kg). The
reference (uncultivated) site's OC content was significantly
(p\textless{} 0.05) higher than the sites under cultivation. The OC
remained constant for some years after the removal of the current oil
palm forest vegetation cover, but after 10 years it was observed that OC
accumulation occurred in both alleys and under heaped fronds, especially
at a depth of 0-20 cm, aside from that the values observed under heaped
fronds were slightly higher. The soil's total nitrogen (TN) was moderate
and ranged from 1.18-2.03 g/kg. The oil palm plantation of 0-5 years and
5-10 years under alley has the same value of 1.18 g/kg at the subsoil.
The overall distribution of nitrogen content followed a similar trend to
the OC distribution and differed significantly with the age of the
plantation.
Exchangeable acidity (EA) was low and fluctuated with the years of oil
palm cultivation. No substantial variation was found between the overall
EA and the age of the plantations and the depth of the soil at
p\textgreater{}0.05. In the uncultivated soil at both depths, the
exchangeable bases were higher than in the different age groups of the
oil palm soils, both in the alleys and under the palm fronds (Tables 1
and 2). According to the Federal Fertilizer Department's ranking (2012),
exchangeable K is low to moderate in both reference soils and oil palm
soils. With respect to the soil depth, the mean average K also showed no
noticeable difference but declined with the depth of the soil. The
soil's exchangeable Na is low and the amount seems too small to raise
some concerns about any potential physical effect of the soil. Compared
to the remaining bases, exchangeable Ca values were greater, followed by
exchangeable Mg. In general, exchangeable Mg values initially appeared
to increase with time in both alleys and under heaped fronds, but
declined gradually with further planting age, while the other bases (Ca,
Na and K) fluctuated with the age of the plantations.
Cation Exchange Capacity (CEC) did show significant variation across the
plantations at p \textgreater{}0.05, it also significant between the
depths (Table 1 and 2). However, at depth of 0-20 cm, the reference
soils had the highest CEC value of 6.15 cmol/kg followed by the 0-5
years plantation the under alleys with 5.50 cmol/kg while the 5-10 years
plantation under heaps had the lowest value of 5.01 cmol/kg. The soil
CEC was low (\textless{} 16 cmol/kg) and decreased with depth. There was
a general increase in the CEC in both layers after 10-15 years of the
alleys and heaped palm fronds to the soil. The percent base saturation
(BS \%) of the soils was greater than 50\%, and the trend is somewhat
inconsistent with the plantation age. The values ranged between 85.3\%
and 93.2\% (Tables 1 and 2).
\textbf{4. DISCUSSION}
The physical and chemical properties of the soil in different land use
may be attributed to differences in the study area's management
practices. Soil texture is an inherent property; spatial variations
between soils with less variation associated with cultivation could be
due to the textural differences found (Brahene et al., 2016). In the
0-20 cm layer, soil bulk density values were comparatively lower when
compared to those of 20-40 cm layer where the content of organic matter
was very low. This suggests that OM has contributed significantly in
enhancing the soil's physical properties, thereby contributing to the
soil's structural stability (Germer and Sauerborn, 2008). The BD values
obtained cannot hinder root development and penetration.
The low pH of the soils can be attributed to the nature of the parent
materials and the high precipitation that causes the basic cations in
the soil to leach intensively (Tweneboah, 2000; Owusu-Bennoah et al.,
2000, Oyegoke et al., 2017). Low pH values connote the presence of a
positively charged colloidal surface capable of attracting negatively
charged ions. The values for oil palm production, however, were
acceptable because they were below 7.5 and did not favor oil palm
production above that value (Okon et al., 2017). Available soil
phosphorus level was low, as the values were between 3-7 mg/kg (Federal
Fertilizer Department, 2012). This means that the amount of phosphorous
is according to the pH status of the oil palm plantations. In this
land-use system, the higher available P content within the forest may be
correlated with an increase in microbial activity.
The high OC content of soils under heaped fronds is related to the
quantity, position, consistency, and temperature and humidity actions on
the pruned fronds compared to those under alleys (Kirschbaum, 2000;
Comte et al., 2012). As a result of the rapid decomposition of palm
fronds, there could be a rise in OC and soil nutrients in planting for
less than 10 years, but as the planting age moved to 25 years, the
decomposition rate slowed down with decomposed material being covered by
overlying palm fronds (Okon et al., 2017). Thus, with the age of the
plantation, it is possible to find heaps of different heights (Brahene
et al., 2016). Total nitrogen (TN) varies with the quantity of organic
matter present in soils, so it has risen without exception, along with
improvements in the related status of organic matter. Relatively, TN
amount is also determined by organic carbon, which in turn results from
plant and root biomass, as well as residues returned to the soil system.
The key cause of N deficiency in tropical soils is extreme leaching and
erosion due to high tropical precipitation (Aweto and Enaruvbe, 2010;
Osinuga and Oyegoke, 2019).
The low level of basic cations in the plantations results from the
effect over time of the continuous uptake of nutrients by the plants.
The result shows that the intensity of weathering, cultivation, and use
of inorganic acid-forming fertilizers affects the distribution of the
cations in the soil system and improves their depletion (Owusu-Bennoah
et al., 2000). The low values observed for these basic cations may also
be due to the low content of organic matter and the presence of low
activity clays of the area (Oyegoke, 2011). Subsequently, the obtained
CEC is a function of the pH and SOM in the soil and, with the age of the
oil palms, the value remained reasonably constant in the soil. This is
an indication that the soils remain low in CEC at their natural pH
levels, demonstrating the soils' low nutrient retention ability.
\textbf{5. CONCLUSIONS}
The study concludes that the distribution of particle size of the soils
studied did not vary significantly because they were formed from the
same parent material (basement complex rocks). Nutrient mining in
plantations is possible as continuous cultivation has been observed to
minimize major and minor plant nutrients. Heaping palm fronds were found
to yield some advantages over time in terms of carbon content, but could
not provide enough nutrients to substitute what the crop used. The rate
of decomposition of organic materials increased with high temperatures,
and the release of nutrients was faster than plants could quickly absorb
and use, and was often subject to losses associated with erosive
precipitation. As pruned fronds and cut plants continue to boost the
structure of the soils to a point that soil bulk density values are
relatively low, the impact of organic matter addition to soils was seen
to be beneficial. The study recommends that the accumulation of organic
residue on the floor of plantations should be championed as it will help
sustain increasing levels of organic matter. It is important to promote
more research on how to efficiently use pruned fronds for compost to be
spread around the oil palm trees.
\textbf{ACKNOWLEDGEMENTS}
The author wishes to appreciate the Directorate of University Farms,
Federal University of Agriculture Abeokuta who allowed me to make use of
their farms and necessary support rendered in the course of the field
work.
\textbf{CONFLICTS OF INTERESTS}
There are no conflicts to declare.
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\textbf{Table 1: Physical and Chemical Properties of Soils under Oil
Palm Alley and Heaps (0-20 cm)}\selectlanguage{english}
\begin{longtable}[]{@{}lllllllllllllllll@{}}
\toprule
\textbf{Plantation} & \textbf{Sand} & \textbf{Silt} & \textbf{Clay} &
\textbf{BD} & \textbf{pH} & \textbf{OC} & \textbf{TN} & \textbf{Avail-P}
& \textbf{H\textsuperscript{+}} & \textbf{AI\textsuperscript{3+}} &
\textbf{Ca} & \textbf{Mg} & \textbf{Na} & \textbf{K} & \textbf{CEC} &
\textbf{BS}\tabularnewline
\midrule
\endhead
\textbf{Age (Years)} &
\textbf{\ldots{}\ldots{}\ldots{}g/kg\ldots{}\ldots{}\ldots{}} &
\textbf{\ldots{}\ldots{}\ldots{}g/kg\ldots{}\ldots{}\ldots{}} &
\textbf{\ldots{}\ldots{}\ldots{}g/kg\ldots{}\ldots{}\ldots{}} &
\textbf{g/cm\textsuperscript{3}} & \textbf{(H\textsubscript{2}O)} &
\textbf{g/kg} & \textbf{g/kg} & \textbf{mg/kg} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\%}\tabularnewline
\textbf{Alley and Reference Soil} & \textbf{Alley and Reference Soil} &
\textbf{Alley and Reference Soil} & \textbf{Alley and Reference Soil} &
\textbf{Alley and Reference Soil} & \textbf{Alley and Reference Soil} &
\textbf{Alley and Reference Soil} & \textbf{Alley and Reference Soil} &
\textbf{Alley and Reference Soil} & \textbf{Alley and Reference Soil} &
\textbf{Alley and Reference Soil} & \textbf{Alley and Reference Soil} &
\textbf{Alley and Reference Soil} & \textbf{Alley and Reference Soil} &
\textbf{Alley and Reference Soil} & \textbf{Alley and Reference Soil} &
\textbf{Alley and Reference Soil}\tabularnewline
0-5 & 758 & 60 & 182 & 1.06 & 6.07 & 12.4 & 1.23 & 5.67 & 0.03 & 0.54 &
2.69 & 1.51 & 0.44 & 0.29 & 5.50 & 89.6\tabularnewline
5-10 & 778 & 50 & 172 & 1.02 & 5.91 & 12.6 & 1.24 & 4.89 & 0.04 & 0.42 &
2.57 & 1.58 & 0.39 & 0.26 & 5.26 & 91.3\tabularnewline
10-15 & 748 & 70 & 182 & 1.13 & 5.98 & 15.2 & 1.41 & 5.64 & 0.04 & 0.46
& 2.43 & 1.78 & 0.33 & 0.28 & 5.37 & 90.7\tabularnewline
15-20 & 728 & 70 & 202 & 0.98 & 5.79 & 15.9 & 1.42 & 5.80 & 0.06 & 0.39
& 2.58 & 1.53 & 0.41 & 0.32 & 5.29 & 91.5\tabularnewline
Uncultivated & 698 & 80 & 222 & 1.23 & 7.13 & 21.7 & 2.03 & 6.21 & 0.02
& 0.40 & 2.86 & 2.02 & 0.51 & 0.34 & 6.15 & 93.2\tabularnewline
\textbf{Heaps and Reference Soil} & \textbf{Heaps and Reference Soil} &
\textbf{Heaps and Reference Soil} & \textbf{Heaps and Reference Soil} &
\textbf{Heaps and Reference Soil} & \textbf{Heaps and Reference Soil} &
\textbf{Heaps and Reference Soil} & \textbf{Heaps and Reference Soil} &
\textbf{Heaps and Reference Soil} & \textbf{Heaps and Reference Soil} &
\textbf{Heaps and Reference Soil} & \textbf{Heaps and Reference Soil} &
\textbf{Heaps and Reference Soil} & \textbf{Heaps and Reference Soil} &
\textbf{Heaps and Reference Soil} & \textbf{Heaps and Reference Soil} &
\textbf{Heaps and Reference Soil}\tabularnewline
0-5 & 748 & 70 & 182 & 1.04 & 6.14 & 12.5 & 1.24 & 5.69 & 0.04 & 0.48 &
2.52 & 1.38 & 0.45 & 0.31 & 5.18 & 90.0\tabularnewline
5-10 & 758 & 60 & 182 & 0.93 & 6.03 & 13.1 & 1.26 & 5.73 & 0.05 & 0.50 &
2.50 & 1.23 & 0.41 & 0.27 & 5.01 & 89.1\tabularnewline
10-15 & 748 & 70 & 182 & 1.11 & 6.08 & 16.5 & 1.79 & 6.02 & 0.03 & 0.57
& 2.48 & 1.42 & 0.34 & 0.30 & 5.14 & 88.3\tabularnewline
15-20 & 718 & 70 & 212 & 1.09 & 5.88 & 17.8 & 1.84 & 6.10 & 0.04 & 0.52
& 2.45 & 1.50 & 0.31 & 0.28 & 5.11 & 86.9\tabularnewline
Uncultivated & 698 & 80 & 222 & 1.23 & 7.13 & 21.7 & 2.03 & 6.21 & 0.02
& 0.40 & 2.86 & 2.02 & 0.51 & 0.34 & 6.15 & 93.2\tabularnewline
\bottomrule
\end{longtable}
\textbf{Table 2: Physical and Chemical Properties of Soils under Oil
Palm Alley and Heaps (20-40 cm)}\selectlanguage{english}
\begin{longtable}[]{@{}lllllllllllllllll@{}}
\toprule
\textbf{Plantation} & \textbf{Sand} & \textbf{Silt} & \textbf{Clay} &
\textbf{BD} & \textbf{pH} & \textbf{OC} & \textbf{TN} & \textbf{Avail-P}
& \textbf{H\textsuperscript{+}} & \textbf{AI\textsuperscript{3+}} &
\textbf{Ca} & \textbf{Mg} & \textbf{Na} & \textbf{K} & \textbf{CEC} &
\textbf{BS}\tabularnewline
\midrule
\endhead
\textbf{Age (Years)} &
\textbf{\ldots{}\ldots{}\ldots{}g/kg\ldots{}\ldots{}\ldots{}} &
\textbf{\ldots{}\ldots{}\ldots{}g/kg\ldots{}\ldots{}\ldots{}} &
\textbf{\ldots{}\ldots{}\ldots{}g/kg\ldots{}\ldots{}\ldots{}} &
\textbf{g/cm\textsuperscript{3}} & \textbf{(H\textsubscript{2}O)} &
\textbf{g/kg} & \textbf{g/kg} & \textbf{mg/kg} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}
cmol/kg \ldots{}.\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}\ldots{}..} &
\textbf{\%}\tabularnewline
\textbf{Alley and Reference (Uncultivated Forest) Soil} & \textbf{Alley
and Reference (Uncultivated Forest) Soil} & \textbf{Alley and Reference
(Uncultivated Forest) Soil} & \textbf{Alley and Reference (Uncultivated
Forest) Soil} & \textbf{Alley and Reference (Uncultivated Forest) Soil}
& \textbf{Alley and Reference (Uncultivated Forest) Soil} &
\textbf{Alley and Reference (Uncultivated Forest) Soil} & \textbf{Alley
and Reference (Uncultivated Forest) Soil} & \textbf{Alley and Reference
(Uncultivated Forest) Soil} & \textbf{Alley and Reference (Uncultivated
Forest) Soil} & \textbf{Alley and Reference (Uncultivated Forest) Soil}
& \textbf{Alley and Reference (Uncultivated Forest) Soil} &
\textbf{Alley and Reference (Uncultivated Forest) Soil} & \textbf{Alley
and Reference (Uncultivated Forest) Soil} & \textbf{Alley and Reference
(Uncultivated Forest) Soil} & \textbf{Alley and Reference (Uncultivated
Forest) Soil} & \textbf{Alley and Reference (Uncultivated Forest)
Soil}\tabularnewline
0-5 & 748 & 70 & 182 & 1.08 & 6.03 & 11.6 & 1.18 & 5.26 & 0.06 & 0.63 &
2.43 & 1.37 & 0.35 & 0.26 & 5.10 & 86.5\tabularnewline
5-10 & 768 & 60 & 172 & 1.03 & 5.86 & 11.7 & 1.18 & 4.43 & 0.05 & 0.72 &
2.48 & 1.56 & 0.25 & 0.19 & 5.25 & 85.3\tabularnewline
10-15 & 728 & 80 & 192 & 1.16 & 5.92 & 12.5 & 1.35 & 5.14 & 0.02 & 0.55
& 2.37 & 1.60 & 0.31 & 0.24 & 5.09 & 89.2\tabularnewline
15-20 & 718 & 70 & 212 & 1.12 & 5.74 & 13.3 & 1.37 & 5.24 & 0.07 & 0.61
& 2.38 & 1.62 & 0.28 & 0.21 & 5.17 & 86.9\tabularnewline
Uncultivated & 688 & 80 & 232 & 1.25 & 7.01 & 20.4 & 1.92 & 5.82 & 0.03
& 0.49 & 2.75 & 1.79 & 0.40 & 0.29 & 5.75 & 91.0\tabularnewline
\textbf{Heaps and Reference (Uncultivated Forest) Soil} & \textbf{Heaps
and Reference (Uncultivated Forest) Soil} & \textbf{Heaps and Reference
(Uncultivated Forest) Soil} & \textbf{Heaps and Reference (Uncultivated
Forest) Soil} & \textbf{Heaps and Reference (Uncultivated Forest) Soil}
& \textbf{Heaps and Reference (Uncultivated Forest) Soil} &
\textbf{Heaps and Reference (Uncultivated Forest) Soil} & \textbf{Heaps
and Reference (Uncultivated Forest) Soil} & \textbf{Heaps and Reference
(Uncultivated Forest) Soil} & \textbf{Heaps and Reference (Uncultivated
Forest) Soil} & \textbf{Heaps and Reference (Uncultivated Forest) Soil}
& \textbf{Heaps and Reference (Uncultivated Forest) Soil} &
\textbf{Heaps and Reference (Uncultivated Forest) Soil} & \textbf{Heaps
and Reference (Uncultivated Forest) Soil} & \textbf{Heaps and Reference
(Uncultivated Forest) Soil} & \textbf{Heaps and Reference (Uncultivated
Forest) Soil} & \textbf{Heaps and Reference (Uncultivated Forest)
Soil}\tabularnewline
0-5 & 748 & 70 & 182 & 1.08 & 6.11 & 12.1 & 1.20 & 5.27 & 0.03 & 0.58 &
2.44 & 1.34 & 0.33 & 0.27 & 4.99 & 87.7\tabularnewline
5-10 & 758 & 60 & 182 & 1.04 & 6.02 & 12.7 & 1.21 & 5.48 & 0.04 & 0.65 &
2.51 & 1.43 & 0.26 & 0.22 & 5.11 & 86.5\tabularnewline
10-15 & 728 & 70 & 192 & 1.15 & 6.06 & 15.4 & 1.49 & 5.73 & 0.03 & 0.61
& 2.50 & 1.52 & 0.28 & 0.21 & 5.15 & 87.6\tabularnewline
15-20 & 718 & 70 & 212 & 1.11 & 5.85 & 16.3 & 1.58 & 5.77 & 0.06 & 0.42
& 2.39 & 1.60 & 0.19 & 0.27 & 4.93 & 90.3\tabularnewline
Uncultivated & 688 & 80 & 232 & 1.25 & 7.07 & 20.4 & 1.92 & 5.82 & 0.03
& 0.49 & 2.75 & 1.79 & 0.40 & 0.29 & 5.75 & 91.0\tabularnewline
\bottomrule
\end{longtable}
\selectlanguage{english}
\FloatBarrier
\end{document}