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American Journal of  
Geospatial Technology (AJGT)

Forms and Distribution of  Phosphorus along A Toposequence at the University of
Benin, Nigeria

Godspower Oke Omokaro1*, Kolawole Agoro Abiola2, Anthonia Bakare2, Edmond Osemwengie Airueghian2, Ikioukenigha Michael3

Volume 3 Issue 1, Year 2024
ISSN: 2833-8006 (Online)

DOI: https://doi.org/10.54536/ajgt.v3i1.2591
https://journals.e-palli.com/home/index.php/ajgt

Article Information ABSTRACT

Received: February 27, 2024

Accepted: March 30, 2024

Published: April 02, 2024

The experiment was conducted at University of  Benin, Nigeria, involving soil samples from 
four toposequence sites (Crest, Middle, Lower, and Bottom) at different depths (0-15 cm, 
15-30 cm, and 30-45 cm). A total of  36 samples were collected and analyzed for various pa-
rameters using standard procedures. The parameters included particle size distribution, pH, 
total organic carbon (TOC), total nitrogen (N), available phosphorus (P), Carbon (C), Hy-
drogen (H), Magnesium (Mg), Potassium (K), Sodium (Na), ECEC, and Aluminum (Al). Re-
sults indicated that pH was lowest in the Crest area (pH 4.10 at 30-45 cm depth) and highest 
in the Bottom area (pH 5.80 at 0-15 cm to 30-45 cm depth). Different soil properties showed 
varying highest values across the toposequence depths. These properties included Total or-
ganic C, Total N, Available P, Ca, K, Mg, H, Na, ECEC, sand content, and the various forms 
of  phosphorus. The correlation table revealed significant positive and negative relationships 
between different forms of  phosphorus and various soil physical and chemical properties. 
The experiment demonstrated distinct variations in soil properties along the toposequence 
sites and depths. The findings contribute to a better understanding of  soil characteristics in 
the studied region, aiding in informed agricultural practices and land management decisions.

Keywords
Slope Gradient, Soil Variability, 
Soil Nutrient, Soil Properties, 
Toposequence

1 Institute of  Ecology, Faculty of  Environmental Engineering, Peoples Friendship University of  Russia named after Patrice 
  Lumumba, Moscow, Russia
2 Department of  Soil Science and Land Management, Faculty of  Agriculture, University of  Benin, Nigeria
3 Department of  Geography and Regional Planning, Igbinedion University, Okada, Mission Road, Edo State, Nigeria
* Corresponding author’s e-mail: omokaro.kelly@gmail.com

INTRODUCTION
One of  the naturally occurring soil forming factors 
that affect soil properties and controlling soil forming 
factors that affect soil properties and control soil erosion 
processes through the redistribution of  soil particles 
and soil organic matter is topography (Ziadat & Taimeh, 
2013). Slope gradient is one of  the important topographic 
factors that influence the process of  drainage; runoff  and 
soil erosion thereby affects physicochemical properties 
(Farmanullah, 2013). Soil loss would normally be expected 
to increase with the increase in slope gradient because 
of  the respective increase in velocity of  surface runoff  
and decrease in infiltration rate (Zhang & Hosoyamada, 
1996). Soils vary in their characteristics primarily because 
of  topography (Amhakhian & Achimugu, 2011) which 
modifies soil water relationships and large extent influences 
on rainfall, drainage, soil erosion, textural composition and 
other soil properties that affect plant growth within a field 
(Atofarati et al., 2012). Topographic variability associated 
with crop production is an integrated reflection on soil 
properties and factors affecting agricultural productivity 
(Dinaburga et al., 2010). The topography of  agricultural 
fields can influence soil physicochemical properties (soil 
depth, texture, and mineral contents), biomass production, 
incoming solar radiation, and precipitation and affect 
crop production. As increased topography/elevation 
significantly increased soil moisture, precipitation, soil 
organic matter and labile carbon, whereas bulk density, pH 
and soil temperature were significantly lower at the higher 
elevations (Griffiths et al., 2009).

The scale of  soil variation depends on the specific soil 
characteristic that is being studied. Some soil properties, 
such as texture, pH, and porosity, are considered to 
be rather spatially static, while other features such 
as soil nitrogen N, soil available forms of  P and K, 
and biological properties are highly spatially variable 
(Piotrowska & Długosz 2012). Soil spatial variability can 
occur across multiple spatial scales, ranging from the 
micro level (millimeters) to the plot level (meters) and 
up to the landscape level (kilometers) (Cobo et al., 2010). 
The aim of  the study was to determine the physical and 
chemical properties of  soils found on Toposequence 
along University of  Benin. The specific objectives were 
to determine the: physical and chemical properties of  the 
soils and Phosphorus forms and distribution in the soil 
of  the study area.

MATERIALS AND METHODS
This study will be carried out at the Ugbowo campus of  
The University of  Benin, Benin City in Edo state, Nigeria. 
The area lies between latitude 6º23ʹ 37ʺ and 6º24ʹ 26ʺ 
North and longitude 5° 36ʹ 25ʺ and 5° 38ʹ 09ʺ East. It is a 
segment of  the coastal plain sand, commonly called acid 
sand of  Nigeria. The natural climate is humid tropics. 
The natural vegetation is rain forest. The rainy season is 
bimodal with peak in July and September. Average rainfall 
is between 1500-2500mm annually. Mean maximum and 
minimum temperature are 31 and 22oC. The soil has been 
mapped as ultisol with Rhodicpaleudult as the modal 
profile (Ogeh and Ogwurike 2006).



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Geography of  Study Site
Point 1: latitude 6.3981630 and longitude 5.6313240

Point 2: latitude 6.3986950 and longitude 5.6352700

Point 3: latitude 6.4021850 and longitude 5.6352700

Point 4: latitude 6.4048320 and longitude 5.6384720

Sample Collection
Soil samples were collected from toposequence site at 
capitol in the University of  Benin, Benin City, Edo State. 
Three different sites were selected for each toposequence 
and samples were collected in each selected site at different 
depths (0-15 cm, 15-30 cm and 30-45 cm) using an auger. 
Soil samples from same depth were bulked to make a 
composite sample. One composite soil sample was then 
prepared from the three sub samples for each soil depth. 
The composite soil samples were then air-dried, mixed 
well and passed through a 2 mm sieve for the analysis of  
selected soil physical and chemical properties. 

Soil Laboratory Analysis
The particle size distribution of  the soil was assessed using 
the hydrometer method by Gee and Or (2002). The clay 
content was determined after 2 hours using the method 
described by Ibitoye (2008). The pH level of  the air-dried 
soil was measured using a glass electrode pH meter with 
a 1:1 ratio, following the procedure outlined by Mclean 
(1982). Prior to the pH measurement, calibration of  the 
pH meter was performed using buffer pH 4.0 and 9.0. 
The electrode was immersed in the liquid portion of  the 
mixture to obtain the reading, which was then recorded. 
Soil organic carbon was determined by the Walkley-Black 
method procedure by wet oxidation using chromic acid 
digestion (Nelson & Sommer, 1996). Exchangeable K, 
Ca Na, and Mg were extracted with a 1 M NH4OAc, 
pH 7 solution. Thereafter, K was analyzed with a flame 
photometer and Ca and Mg were determined with an 
atomic absorption spectrophotometer (Okelabo et al., 
2002). Exchangeable acidity procedures and results were 
reported in Cmolkg-1 according to the method described 
by Black (1965). Total N was determined using micro-
Kjeldahl digestion and distillation techniques (Bremner, 
1996); Available P was determined by Bray-1 extraction 
followed by molybdenum blue colorimetry (Frank et al., 
1998), Total phosphorus in the soils was determined by 
perchloric acid digestion and Inorganic P was fractionated 
by method.

Determination of  Phosphorus as Aluminum 
Phosphate (Al-P)
One gram of  air-dried soil (2 mm sieve) was weighed out 
placed in 250 ml plastic container. 35 ml of  I N NH4Cl 
was added, and the mixture shaken on a mechanical 
shaker for 30 minutes. To remove water soluble and 
loosely bound P and exchangeable Ca, the suspension 
was filtered (Whatman filter paper No. 42) and the 
filtrate discarded, leaving the soil residues. To the residues 
in the plastic bottle were added 35 ml of  0.5 N NH4F, 
covered tightly and shaken for 1hr on a mechanical 

shaker. The mixture was filtered, and the clear filtrates 
were used for Al-P determination. The soils residues in 
the plastic bottle were reserved for Fe-P extraction. For 
Al-P determination, aliquots (10 ml) of  the extract were 
pipetted out into 50 ml volumetric flask and 15 ml boric 
acid added (0.8 M). Blue colour was developed using 
4 ml of  reagent B solution and made up to mark with 
distilled water. Absorbance readings were recorded at 
660 nm wavelength using the UV/VIS Unicam spectro-
colorimeter

Phosphorus Determination as Iron Phosphate (Fe- P)
The soil residue saved after Al-P extraction was washed 
twice with 25 ml saturated NaCl and filtered each time and 
the filtrate discarded. Thereafter, 35 ml 0.1 N NaOH was 
added to the plastic bottles, covered tightly and shaken for 
17 hours. The suspensions were filtered, and clear extract 
collected for Fe-P determination. The soil residues in the 
plastic bottle were reserved for Ca- P extraction. For Fe 
–P determination, 5 ml aliquot of  the clear solution was 
pipetted into 50 ml volumetric flask, 4 ml of  reagent B 
was added for the blue colour development and made up 
to mark with distilled water. Absorbance readings were 
recorded at 660 nm wavelength using a UV/VIS Unicam 
spectro-colorimeter.

Phophorus Determination as Calcium Phosphate 
(Ca-P)
The soil residues saved after the Fe-P extraction was 
washed twice with 25 ml saturated NaCl solution (10%), 
filtered each time and discarded, 35 ml of  0.5 N H2SO4 
was added to the soil in the plastic bottles, covered tightly 
and shaken on the mechanical shaker for I hour. The 
suspensions were filtered, and clear solution obtained. 30 
ml aliquot of  the clear solution was pipetted into 50 ml 
of  volumetric flask, 4 ml of  the reagent B was added for 
colour development, and the volume made up to mark 
with distilled water. Absorbance readings were recorded 
at 660 nm wavelength using a UV/VIS Unicam spectro-
colorimete.

Determination of  Total Phosphorus and Occluded 
Phosphorus
One gram of  finely ground (0.5 mm scene) soil was 
weighed out each into 250 ml conical flasks and 25 ml 
of  HNO3, 4 ml of  perchloric acid and 2 ml of  H2SO4 
added respectively and mixed thoroughly. It was digested 
on a heater inside a fume cupboard until the colour due to 
organic matter disappeared. Then additional 20 minutes 
heating was allowed to dry completely. At this stage 
heavily white fumes due to HNO3, HClO4 and H2SO4 
appeared, and the insoluble materials looked like white 
sand. The flask was shaken occasionally during digestion. 
The digest was allowed to cool, and 70 ml of  distilled 
water was added to the digest and heated to warm. The 
suspension was filtered into 250 ml volumetric flask and 
made up to mark with distilled water. Then, 10 ml aliquot 
was pipetted into 50 ml volumetric flask, 4 ml of  the 



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Am. J. Geo Spat. Technol. 3(1) 1-8, 2024

reagent B was added and made up to mark with distilled 
water. The absorbance reading was recorded at 660 nm 
wavelength using a UV/VIS Unicam spectro-colorimeter. 
The occluded phosphorus (inactive P) was calculated as 
the difference between the total phosphorus and the 
active phosphorus (Al-P, Fe-P, Ca-P). 

Statistical Analysis
Plant parameters measured were subjected to analysis of  
Variance (ANOVA) using GENSTAT 8th Edition while 
Duncan’s New Multiple Range Test was used to separate 
the means at 5% level of  probability.

RESULTS AND DISCUSSION
Effect of  Toposequence on Soil Properties
Table 1 displays the physical and chemical properties of  
soil across different toposequence depths at the University 
of  Benin, Benin City. The pH values were acidic in all 
Crest depths (0-15 cm: 4.60, 15-30 cm: 4.90, 30-45 cm: 
4.10) and Middle depths, remaining consistently acidic. 
Lower depths showed a strong acidic trend (pH 5.5 to 

5.0), while Bottom depths were moderately acidic (pH 
5.80). Total nitrogen (N) varied with depths, ranging from 
low (Crest 0-15 cm: 1.0) to moderately low (Crest 30-45 
cm: 1.30). Bottom 30-45 cm had the highest N (1.95 g/
kg), and Lower 30-45 cm had the lowest (0.90 g/kg). Total 
organic carbon (C) increased with soil depths across all 
toposequence. Crest 30-45 cm had the highest C (17.00 
g/kg - High), while Middle 30-45 cm had the lowest (7.10 
g/kg - moderate), and the findings align with Chude et 
al., (2011).
Cation exchange capacity (CEC) varied among 
toposequence and decreased with depth. Middle had the 
highest CEC values at various depths (11.04 cmolkg-1, 
11.56 cmolkg-1), indicative of  soil productivity and 
useful for phosphorus, potassium, and magnesium 
recommendations. High CEC values relate to organic 
matter and clay content, offering more negative 
electrostatic sites for positive cation attraction. These 
results support Vogelmann et al. (2010) findings on CEC 
correlation with organic matter and pH levels.

Table 1:  Physical and Chemical Properties of  Soils under various Toposequence

To
po

se
q.

D
ep

th
(c

m
)

pH

T
O

C

T.
N

PO
4

H
   

A
l

K C
a

N
a 

  

M
g

E
C

E
C

Sa
nd

Si
lt

C
la

y 
 

T
C

⭢g/kg⭠ mg/kg ⭢ cmol/kg ⭠ ⭢ g/kg ⭠

  C
re

st

0-
15

4.
60

15
.4

0

1.
9

3.
91

0.
50

0.
00

0.
08

    

0.
96

0.
10

0.
65

2.
29

67
7.

20

80
.0

0

24
2.

80

SL

15
-3

0

4.
90

9.
50

1.
1

1.
35

0.
60

0.
00

0.
21

0.
80

0.
10

0.
65

2.
36

80
1.

20

20
.0

0

17
8.

80

SL

30
-4

5

4.
10

17
.0

0

1.
95

2.
38

0.
40

0.
00

0.
04

0.
64

0.
10

0.
97

2.
15

79
1.

20

20
.0

0

18
8.

80

SL

  M
id

dl
e

0-
15

4.
60

11
.2

0

1.
15

7.
67

0.
50

0.
00

0.
19

0.
96

0.
10

0.
97

2.
72

87
7.

20

30
.0

0

92
.8

0

SC
L

15
-3

0

4.
30

9.
00

1.
08

2.
61

0.
50

0.
00

0.
04

0.
96

0.
10

0.
97

2.
57

79
7.

20

50
.0

0

15
2.

80

SC
L

30
-4

5

4.
40

7.
10

0.
9

6.
61

0.
40

0.
00

0.
14

0.
80

0.
09

0.
97

2.
4

73
7.

20

30
.0

0

23
2.

80

SC
L

  L
ow

er

0-
15

5.
50

11
.8

0

1.
2

42
.3

5

0.
40

0.
00

0.
10

8.
50

0.
10

1.
94

11
.0

4

76
8.

20

25
.0

0

20
6.

80

SC
L

15
-3

0

5.
20

11
.0

0

1.
11

21
.2

3

0.
40

0.
00

0.
14

9.
30

0.
10

1.
62

11
.5

6

75
8.

20

75
.0

0

16
6.

80

SL

30
-4

5

5.
00

12
.8

0

1.
3

19
.9

4

0.
50

0.
00

0.
10

5.
61

0.
10

0.
65

6.
96

77
8.

20

69
.0

0

15
2.

80

SL

  B
ot

to
m

0-
15

5.
80

8.
80

1 9.
25

0.
40

0.
00

0.
15

5.
29

0.
12

0.
65

6.
61

66
8.

20

55
.0

0

27
6.

80

SL

15
-3

0

5.
80

11
.8

0

1.
2

6.
06

0.
30

0.
00

0.
21

6.
09

0.
09

0.
97

7.
66

64
8.

20

35
.0

0

31
6.

80

LS



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30
-4

5

5.
80

10
.6

0

1.
16

5.
11

0.
40

0.
00

0.
16

4.
33

0.
11

0.
97

5.
97

66
8.

20

55
.0

0

27
6.

80

SL

Where: TC = Textural Class, SL = Sandy loam, SCL = Sandy clay loam, LS = Loamy sand 

Table 1 further presents the results of  soil separates 
from different toposequence locations. All land use types 
predominantly exhibited sandy texture (sand fraction: 
877.20-801.20 g/kg, silt fraction: 80-20 g/kg, clay 
fraction: 318.80-92.80 g/kg). Sand content increased with 
depth, while clay content decreased. Soil texture remained 
similar across toposequence, as it is not significantly 
influenced by soil management or toposequence variation 
(Oyedele et al., 2009). Hydrogen (H) content ranged from 
0.30-0.60 cmol/kg across the toposequence. The highest 
H value (0.60 cmol/kg) was at Crest, depth 15-30 cm, 
while the lowest (0.30 cmol/kg) was at Bottom, depth 
15-30 cm. Hydrogen content was relatively consistent 
throughout the toposequence. Aluminium (Al) was 

not detected at any toposequence depth, indicating its 
absence throughout the area.
Available phosphorus content varied across toposequence. 
Bottom had moderate (9.25 mg/kg), low (6.06 mg/kg), and 
low (5.11 mg/kg) P content. Lower had high (42.35 mg/
kg) and moderate (19.94 mg/kg) P content at 30-45 cm 
depth; Middle had low P content (7.61 mg/kg, 2.61 mg/kg, 
and 6.61 mg/kg). Crest exhibited low P content (3.91 mg/
kg) at 0-15 cm depth and very low P content (1.35 mg/kg, 
2.38 mg/kg) at other depths (Chude et al., 2011). Higher 
phosphorus content in Lower may be due to its higher 
organic matter content, while lower phosphorus content in 
other areas could be attributed to fixation, abundant crop 
harvest, and erosion impacts (Yeshanch, 2015).

Table 2:  Phosphorus availability on different toposequence site
Slope Depth (cm) Ca-P Al-P Fe-P Occluded-P Total-P

⭢ (mg/kg) ⭠
Crest 0-15 4.73 29.51 15.19 81.41 96.59

15-30 3.73 34.52 16.90 81.74 98.64
30-45 2.58 43.26 15.33 110.74 126.06

Middle 0-15 1.43 74.49 122.63 411.92 534.55
15-30 6.02 33.95 63.32 17.72 81.04
30-45 5.44 33.95 34.95 50.18 85.13

Lower 0-15 7.74 20.63 12.18 150.32 162.49
15-30 7.16 16.62 7.88 151.75 159.63
30-45 3.44 15.04 8.02 118.45 126.47

Bottom 0-15 7.45 73.20 8.45 307.94 316.39
15-30 6.45 16.90 9.17 170.92 180.09
30-45 2.44 9.88 12.61 96.68 109.28

Total Phosphorus
As shown in Table 2, the total P content in all the 
profiles varied from 81.04 to 534.55μg g-1 with a mean of  
173.03μg g-1. These values are comparable to the values 
reported by Adeleye and Omueti (2006) for some soils 
derived from basement complex parent material. Total 
P was generally highest in the lower slope and lowest at 
upper slope. Also, total P was highest in the topsoil of  
crest apart from that of  depth (30-45). This trend could 
be due to accumulation of  litters on the topsoil as also 
suggested by Osodeke and Osondu (2006).
Ca –P varied from 9.88 to 74μg g-1 with a mean of  33.5μg 
g-1, Al – P varied from 1.43 to 7.74μg g-1 with a mean of  
4.88μg g-1, Fe – P varied from 7.88 to 122.63μg g-1 with 
a mean value of  27.4μg g-1, Occluded – P varied from 
17.72 to 411.92μg g-1 with a mean value of  145.8μg g-1. Ca 
– P had the least value among the active P forms while the 
Occluded – P had the highest value. This could probably 

be due to the acidity nature of  the soils and the fact that 
it is the most soluble of  the inorganic forms and tends to 
revert to the less soluble iron and aluminium phosphate 
in acid soils as suggested by Aghimien et al. (1988). Al – P 
is the least soluble of  the inorganic P fraction and tends 
to accumulate at the expense of  the more soluble Al – 
P and Ca P and this accounted for the relatively higher 
content of  iron phosphate in the acidic soils (Agbimien 
et al., 1988).
Mokwunye and Bationo (2002) also reported that the 
main sources of  plant available P in soils are generally 
accepted as active P form rather than inactive P form. 
And secondary Phosphate as Al-P, Fe – P and Ca – P 
increase in content with strengthening of  weathering and 
pedogenesis in the soil. Lambers et al. (2008) suggested 
that relationship exist between P content and forms in 
soils and stages of  soil development. All soil P is in the 
primary mineral form (mainly Al- P and Ca – P mineral) 



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at the beginning of  soil development. With time, these 
inorganic P weather giving rise to P in various other forms 
mainly organic P (reservoir) occluded P and available P.

Correlation Matrix
Correlation coefficient for Crest
Table 3 shows the correlation coefficient (r) between 
forms of  P (Al-P, Ca-P, Fe-P, Occluded-P and Total-P) 
with some soil of  physical and chemical properties of  

toposequence at crest. Iron forms of  P were positively and 
significantly correlated with Clay (r=0.997), K (r=0.997) 
at (P<0.05) but negatively and significantly correlated 
with Sand and Silt (r=0.997), (r=0.997) at (P<0.05). Total 
form of  P were negatively and significantly correlated with 
pH (r=0.998) at (P<0.05) having other forms of  P (Al-P, 
Ca-P, Fe-P and Occluded-P) not positively nor negatively 
significantly correlated with some soil of  physical and 
chemical properties of  toposequence at the Crest Level.

Table 3: Crest Correlation Coefficient
CREST AL-P Ca-P Fe-P Occluded-P Total-P
Av. P -0.897 -0.993 -0.368 -0.685 -0.722
Ca -0.668 0.578 0.796 -0.887 -0.861
Clay -0.155 0.040 0.997* -0.491 -0.445
EC -0.995 0.977 0.182 -0.967 -0.979
ECEC -0.514 0.412 0.897 -0.782 -0.748
H 0.155 -0.040 -0.997 0.491 0.445
K 0.001 -0.116 0.997* -0.350 -0.300
Mg 0.778 -0.845 0.562 0.508 0.533
Na -0.177 0.289 -0.966 0.179 0.127
O.M 0.464 -0.563 0.845 0.124 0.176
Sand 0.155 -0.040 -0.997* 0.491 0.445
Silt 0.155 -0.040 -0.997* 0.491 0.445
Total N 0.646 -0.913 -0.378 0.337 0.386
pH -0.933 0.885 0.435 -1.000 -0.998*

Table 4: Middle Correlation Coefficient
Middle AL-P Ca-P Fe-P Occluded-P Total-P
Av. P 0.999* -0.986 0.963 0.992 0.998*
Ca 0.311 -0.198 0.596 0.239 0.303
Clay 0.918 -0.958 0.744 0.945 0.921
EC -0.987 0.999 -0.885 -0.996 -0.998
ECEC 0.408 -0.299 0.676 0.339 0.401
H -0.500 0.396 -0.749 -0.434 -0.493
K -0.500 0.597 -0.200 -0.563 -0.507
Mg 0.692 -0.603 0.885 0.636 0.686
Na -0.500 0.597 -0.200 -0.563 -0.507
O.M -0.063 -0.053 0.376 0.011 -0.055
Sand ____ -0.116 -0.317 0.074 0.008
Silt -0.994 1.000* -0.908 0.999* -0.995
Total N -0.030 -0.686 -0.346 0.044 -0.023
pH 0.918 0.865 0.996 0.998 0.915

Correlation Coefficient for Middle
Table 4 shows the correlation coefficient (r) between 
forms of  P (Al-P, Ca-P, Fe-P, Occluded-P and Total-P) 
with some soil of  physical and chemical properties of  
toposequence at middle. Al-P and Total-P were positively 
and significantly correlated with Available P (r=0.999) and 

(r=0.998) at (P<0.05) respectively; Ca-P and Occluded-P 
were positively and significantly correlated with Silt 
(r=1.000) and (r=0.999) at (P<0.05) respectively, but 
Fe-P were not positively nor negatively and significantly 
correlated with some physical and chemical properties of  
toposequence at Middle.



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Correlation Coefficient for Lower
Table 5 shows the correlation coefficient (r) between forms 
of  P (Al-P, Ca-P, Fe-P, Occluded-P and Total-P) with some 
soil of  physical and chemical properties of  toposequence 
at lower. Ca-P were negatively and significantly correlated 
with Total N (r =-0.986) at (P<0.05), Fe-P were positively 
and significantly correlated with Mg (r = 1.000) at (P<0.05). 

Occluded-P were positively and significantly correlated with 
H and Na (r = 0.999), (r = 0.999) at (P<0.05) respectively. 
Total-P were positively and significantly correlated with 
Ca and H (r = 0.997), (r = 0.997) at (P<0.05) respectively 
while Al-P were not positively nor negatively correlated 
with some soil of  physical and chemical properties of  
toposequence at lower.

Table 5: Lower Correlation Coefficient
Lower AL-P Ca-P Fe-P Occluded-P Total-P
Av. P 0.431 -0.198 0.683 0.354 -0.250
Ca 0.718 0.992 0.475 0.999 0.997*
Clay -0.947 -0.950 -0.805 -0.887 -0.932
EC 0.936 0.536 0.999 0.392 0.491
ECEC 0.961 0.935 0.832 0.865 0.915
H 0.718 0.992 0.475 0.999* 0.997*
K 0.547 -0.065 0.774 -0.226 -0.118
Mg 0.962 0.604 1.000* 0.467 0.561
Na 0.718 0.992 0.475 0.999* 0.997
O.M 0.979 0.904 0.872 0.824 0.881
Sand 0.987 0.886 0.892 0.800 0.861
Silt -0.243 0.388 -0.525 0.533 0.437
Total N 0.880 -0.986* 0.696 0.951 0.979
pH 0.991 0.871 0.906 0.994 0.843

Correlation Coefficient for Bottom
Table 6 show Occluded-P and Total P were positively and 
significantly correlated with EC (r =0.998), (r = 0.999) 
at (P<0.05) respectively, while Al-P, Ca-P and Fe-P were 

not positively nor negatively and significantly correlated 
with some soil of  physical and chemical properties of  
toposequence at bottom.

Table 6: Bottom Correlation Coefficient
Bottom AL-P Ca-P Fe-P Occluded-P Total-P
Av. P 0.871 0.297 -0.271 0.721 0.729
Ca 0.912 0.945 -0.936 0.986 0.984
Clay 0.971 0.542 -0.519 0.880 0.885
EC 0.981 0.847 -0.832 0.998* 0.999*
ECEC 0.287 0.866 -0.879 0.517 0.508
H 0.101 0.756 -0.774 0.346 0.336
K -0.194 0.532 -0.555 0.657 0.046
Mg -0.585 -0.982 0.987 -0.769 -0.762
Na 0.995 0.654 -0.634 0.938 0.942
O.M 0.217 -0.512 0.535 -0.034 -0.023
Sand -0.985 -0.598 0.576 -0.910 -0.915
Silt 0.585 0.982 -0.987 0.769 0.762
Total N 0.361 -0.377 0.402 0.117 1.000
pH 0.996 0.785 -0.768 0.987 0.988

DISCUSSION
The study shows a very low positivity, negativity and 
significantly correlated with soil properties and that can 
be traceable to; Phosphorus been a major limiting factor 

in the growth and function of  many forest, because P 
is a mineral nutrient derived from the weathering of  
rocks and drift where it deficiencies tend to become 
more acute as landscapes and soils age due to progressive 



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Am. J. Geo Spat. Technol. 3(1) 1-8, 2024

leaching and sequestration (Vitousek, 2004). P deficiency 
is particularly widespread in rain-fed upland farming 
systems throughout the tropics and remains a major 
plant nutrient constraint. It is also attributed to some 
combination of  soil parent material, soil age, topography, 
climate, and biological activity, high weathering intensity 
and loss by soil erosion (Fairhurst et al., 1999). Paulos 
(1996) indicated that the concentrations of  active P forms 
were related to the degree of  chemical weathering. Hence, 
all the forms of  P can exist in all soils, but P bound by Al 
and Fe is abundant in highly weathered acidic soils and 
such is the case of  the study area.

CONCLUSION
Phosphorus is an essential nutrient that is utilized for 
energy transport and growth by all organisms, where it 
is involved in many critical biological processes, such as 
energy metabolism, the synthesis of  nucleic acid, and 
photosynthesis, and is highly needed in this study location 
as to help increase its availability for plant growth and 
metabolism.

Acknowledgment
The work is that of  Bachelor of  Agriculture project 
registered at the Department of  Soil Science and Land 
Management, Faculty of  Agriculture, University of  
Benin, Nigeria. Special thanks to Dr. Mrs. Anthonia 
Bakare for guidance.

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