# Assessing Spatial Variability of Soil Physical and Chemical Quality as Affected by Slope Curvature and Aspect of Acid Soils in Akwa Ibom State, Nigeria

Essien, O. A, Hogan, E. D, Akata, O. R, Enyong, J. K, Ben, F. E

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Essien, O. A, Hogan, E. D, Akata, O. R, Enyong, J. K, Ben, F. E. Assessing Spatial Variability of Soil Physical and Chemical Quality as Affected by Slope Curvature and Aspect of Acid Soils in Akwa Ibom State, Nigeria. Asian Journal of Agriculture and Allied Sciences, 2025, 8 (1), pp.197 - 210. 10.56557/ajaas/2025/v8i165. hal-05014958

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# Assessing Spatial Variability of Soil Physical and Chemical Quality as Affected by Slope Curvature and Aspect of Acid Soils in Akwa Ibom State, Nigeria

Essien, O. A. a*, Hogan, E. D. a, Akata, O. R. b, Enyong, J. K. b and Ben, F. E. b

a Department of Soil Science, Akwa Ibom State University, Obio Akpa Campus, Oruk Anam, Nigeria.
b Department of Crop Science, Akwa Ibom State University, Obio Akpa Campus, Oruk Anam, Nigeria.

## Authors' contributions

This work was carried out in collaboration among all authors. All authors read and approved the final manuscript.

## Article Information

DOI: https://doi.org/10.56557/ajaas/2025/v8i165

**Open Peer Review History:**

This journal follows the Advanced Open Peer Review policy. Identity of the Reviewers, Editor(s) and additional Reviewers, peer review comments, different versions of the manuscript, comments of the editors, etc are available here: https://prh.ikprress.org/review-history/12918

## Original Research Article

Received: 24/01/2025

Accepted: 26/03/2025

Published: 29/03/2025

## ABSTRACT

The study was conducted to evaluate the spatial variability of soil physical quality affected by slope aspect and curvature in acid soils of Akwa Ibom State, Nigeria. Twenty-four soil samples were collected from three locations in three slope positions on two slope characteristics in the study area. The soil samples were air-dried and sieved through 2mm sieve for the determination of the physical and chemical properties of the soil. Indices of soil quality (modified clay ratio, silt clay ratio, sodium

<footnote>*Corresponding author: E-mail: otobongessien@aksu.edu.ng;</footnote>
absorption ratio, weight of organic matter) were calculated. The data generated were summarized using descriptive statistics and correlation analysis was used to determine the relationship between slope curvature and aspect with physical properties of the soil. The results show that in physical properties, south facing slope recorded higher sand, Bulk density and Total porosity (922.33 %, 27.83 %, 1.61 Mgm⁻³and 0.76 m³m⁻³) respectively, while north-facing had high clay and low hydraulic conductivity (59 % and 4.10 cmhr⁻¹) respectively. In slope curvature, concave slope recorded high mean content of silt, Bulk density and Total porosity (26 %, 2.45 Mgm⁻³ and 0.81 m³m⁻³) respectively, the convex slope had a high content of silt, clay and saturated hydraulic conductivity (919 %, 58.83 % and 4.14 cmhr⁻¹) respectively. The results of soil chemical properties in comparing the slope aspect indicated that north-facing slope recorded a high mean value in pH (6.04) and base saturation (51.73 %), while south facing slope recorded high mean value in organic matter (3.90 %), available phosphorus (5.81 mgkg⁻¹), calcium (17.77 cmolkg⁻¹), magnesium (1.17 cmolkg⁻¹), potassium (0.30 cmolkg⁻¹), sodium (0.38 cmolkg⁻¹), exchangeable acidity (5.04 cmolkg⁻¹), and effective cation exchange capacity (9.50 cmolkg⁻¹). Results on indices of soil physical properties in north facing slope had mean value of (19.59, 0.18, 673 and 17.65) for Silt Clay Ratio (SCR), Sodium Adsorption Ratio (SAR), Weight of Organic Matter (WOM) and Modified Clay Ratio (MCR), respectively, while south facing slope had 20.34, 0.46, 780 and 30.78, for SCR, SAR, WOM and MCR respectively. Concave slope had mean values of 18.02, 0.20, 739 and 15.94 for SCR, SAR, WOM and MCR respectively. Convex slope indicated mean values of 18.55, 1.20, 67 and 17.70 for SCR, SAR, WOM and MCR respectively.

Keywords: Soil physical properties; spatial variability; slope aspect; slope curvature; acid soils.

# 1. INTRODUCTION

Acid soils in Akwa Ibom State vary in quality of soil properties as affected by slope characteristics. Akwa Ibom State is a tropical rain forest, affected by water erosion, which slope is one of the key factors that speed up acceleration of water erosion, that weaken the bonds that bind aggregate together, detachment of individual particle, splash, translocation of soil particles and then carried by agent of erosion, which leads to on site and off-site effect (Akata et al., 2024a). Therefore the knowledge of soil physical and chemical quality attributes is important in developing stable and viable soil management practices that will conserve the soil resources base and its properties, soil quality generally can be defined as the degree of fitness of a soil for a specific use (Carter et al., 1997). Soil quality also implies other concepts such as the sustained capability of soil to accept, store, and recycle water, nutrients and energy. It is a unique balance and interaction of its physical, chemical and biological components (Umoh et al., 2021; Karlen et al., 1997; Herrick et al., 2002; Aparicio & Costa, 2007).

Soil quality is dynamic and often assessed based on soil function (Doran & Parkin, 1996; Simeon et al., 2023), to ascertain whether it is improving, stable or declining with soil use (Essien et al., 2024a; Essien et al., 2024b; Akata et al., 2024b; Enyong, et al., 2021). This is because it is

deemed important for the assessment of the extent of land degradation or amelioration, and for identifying management practices for sustainable land use (Sam et al., 2025; Akpan et al., 2025; Ben et al., 2024; Essien et al., 2025). Consequently, good soil physical quality occurs when soils exhibit the absence of degradation symptoms such as poor water infiltration, which reflects poor soil structure (Enyong et al., 2013).

Soil physical properties profoundly influence how soils function in an ecosystem and how they can best be managed (Weil & Brady, 2017; Essien et al., 2023a; Akpan et al., 2024). Soil physical quality, also termed soil physical fertility, is the component contribution of the soil's physical properties and processes to the ability of the soil to perform its functions and support ecosystem services (Scott, 2000; Yaalon & Arnold, 2000; Essien et al., 2023b). Shukla (2014) stated that the quality of land is dependent on its physical properties. Lal (1999) and Lal and Shukla (2005) reported that high soil physical quality plays an important role in enhancing soil chemical and biological qualities and hence in defining the overall productivity of the soil (Akpaninyang et al., 2022; Akpan et al., 2023; Liu et al., 2020), as well as in sustainable management of natural resources.

It is common knowledge that topography significantly affects soil characteristics (Mark et al., 2024; Essien et al., 2024c; Ogban et al., 2022; Essien and Ogban, 2018) because it is
slope element drives geomorphic processes (Evans, 1972), retard (Weil & Brady, 2017) and cause the convergence or divergence of fluxes of materials on the landscape. Therefore, soils differ in their characteristics primarily because of topography (Essien et al., 2024c), and because topography modifies the climate elements (Weil & Brady, 2017).

Natural slopes are formed due to physical processes that include plate tectonics and weathering/erosion of rock masses that results in material deposition. Slope is important to soil formation and management because it influences runoff, soil drainage and erosion, the use of machinery and choice of crops (Ogban, 2021). The slope is commonly expressed in percentage. The percentage of slope is determined by measuring the difference in vertical elevation in feet over 100 feet of horizontal distance (Eshetu & Lemma, 2024). The shape of the slope is another important characteristic. A convex slope curves outward like the outside surface of a ball, a concave slope curves inwardly like the inside surface of a saucer, and a plane slope is like a tilted surface. Weil and Brandy (2017) stated factors that influence slope stability of an embankment which include; Shear strength of the soil, Unit weight, Embankment height, Slope steepness, and Pore pressure within the soil.

The main objective of the study was to evaluate the spatial variability of soil physical quality affected by slope curvature and aspect in soils of Akwa Ibom state, Nigeria. Since there's death information on spatial variability of soil physical quality, hence it is necessary to evaluate the spatial variability of soil physical quality affected by slope curvature and aspect on acid soils of Akwa Ibom state, Nigeria.

## 2. MATERIALS AND METHODS

### 2.1 Location of the Study Area

The study was carried out in slopes in an acid soil of Akwa Ibom state, Southern Nigeria. Akwa Ibom state is situated between latitude 4°ss 30¹ N and 5° 30¹ N and longitude 7° 30° E and 8° 20¹ E. The climate of the study area was typically humid tropical. The area was within the wet, humid rainforest zone of West Africa which has two distinct seasons: wet and dry season also known as rainy and dry season. The rainy season occurs during the month of April through the month of August known as "August Break" during the long rainy season. The area has a

mean annual rainfall range of 2000 – 2500 mm, annual temperature ranges from 24°C - 30°C and a relative humidity range of 75 – 79 % (SLUS-AK, 1989).

Akwa Ibom state has geological material which are grouped into the periods namely; Cretaceous, tertiary and recent. The Cretaceous was characterized by the relatively warm climate at high seas level and creating numerous shallow island seas. The tertiary comprises the coastal plain sands, shale, sand stones and beach ridge sands. The recent geology materials are the alluvial deposition. Coastal plain sands account for more than 75 % of the soils of Akwa Ibom State. The soils of this area is a typical Tropohumult fine-loamy, Kaolinite, Isohyperthemic formed from coastal plain sands parent materials and is classified as an Ultisols based on the United States Department of Agriculture (USDA) System of classification (Soil Survey Staff, 1999). The main vegetation of the study area has been the tropical rainforest, though it has been destroyed through human activities. The greater part of the area is now covered by secondary bush which constitutes trees, shrubs, legumes and vegetation re-growth. They are prone to intermediate cuttings, bush clearing and intensified shifting cultivation pressure. The study area has rainforest vegetation characterized by plant types arranged in tiers. The vegetation are shrub due to excessive deforestation. Oil palm (Elaeis guineensis) dominates other plants.

The major use of the land in the area is for agriculture, building and road construction. The general land use pattern of cultivation is bush fallow system, after few years the intensive use of a piece of land is left for some years without use to fallow. This system, like the shifting cultivation gives the field a chance of rest for a number of years, it allows for thick vegetation re-growth which by natural process sheds leaves.

### 2.2 Field Method

Soil samples were collected in three local Government Areas (Oruk Anam, Essien Udim and Etinan), in Akwa Ibom State, in three slope positions (upper, middle and lower slopes). Two slope characteristics were considered for the study, Slope Curvature (Concave and Convex Slopes) and Slope Aspect (South Facing and North Facing Slopes). Auger soil samples were collected and bulk for particle size distribution and chemical properties, while core samples
were collected at each sampling point with core cylinder measuring 7.2cm long and 6.8cm wide for bulk density, total porosity and hydraulic conductivity.

## 2.3 Laboratory Analysis

Soil samples were air dried and passed through a 2mm sieve for the following analysis;

## 2.4 Physical Properties of the Soil in the Study Area

**Particle Size Analysis:** Particle size distribution was determined using Bouyoucos method as derived by Udo et al., (2009). After dispersing the soils particles with sodium carbonate and sodium hexametaphosphate solution, the textural class of the soil was determined using the textural triangle.

**Bulk Density:** Bulk density was determined using core sample as described by (Grossman & Reinish, 2002). Soil samples were oven dried at 105°C to a constant weight and bulk density calculated;

Using the equation;

$$BD = Ms/Vt$$

Where;

BD = Bulk density (mgm-3)

Ms = Mass of oven dry soil (mg)

Vt = total volume of soil (m3)

The total volume of soil was calculated from internal dimension of the cylinder.

**Total Porosity:** Total porosity was calculated from particle size and bulk density relationship as follows; (Grossman & Reinish, 2002).

Where

P = Total porosity (m³ m⁻³)

Bd = Bulk density (mg m⁻³)

s = Particle size (mg m⁻³)

**Saturated Hydraulic Conductivity:** Saturated hydraulic conductivity (Ksat) was determined using the constant head parameter method (Dane & Topp, 2002). The core sample was placed in a basin of water and allowed to be saturated by capillary. The saturated core samples were then placed in a funnel and a

cylinder head was then placed on it to a given level which was constantly maintained throughout the experiment. The cylinder head was held to core cylinder with masking tape. The water passing through the soil column was collected into a measuring cylinder and the saturated hydraulic conductivity was calculated using the equation;

$$K_{sat} = QL/h A_t$$

Where,

Ksat = saturated hydraulic conductivity (cm3 hr⁻¹)

Q = discharge rate (cm3 min⁻¹)

L = length of soil column (cm)

h = change in hydraulic head (cm)

A = cross sectional area through which the flow takes place (cm²)

t = time (minutes)

## 2.5 Chemical Properties

**Soil pH:** pH was determined using a glass electrode pH meter and INKCL at 1:2.5 soil water ratio (Udo et al., 2009).

**Organic Carbon:** Organic carbon was measured by Walkly and Black digestion method (Gee & Or, 2002).

**Organic Matter:** Organic matter was calculated by multiplying organic carbon by Van Bemmelen factor of 1.724 (Udo et al., 2009).

**Total Nitrogen:** Total nitrogen was determined by - Kjeldhal digestion method and distillation method (Udo et al., 2009).

**Exchangeable Cation:** Exchangeable cation was determined by the method described by (Grossman & Reinish, 2002). The amount of potassium (K) and sodium (Na) was determined using flame photometer while magnesium (mg) and calcium (ca) were determined by atomic absorption spectrometer (AAS).

**Base Saturation:** Base saturation was determined as a sum of exchangeable basic cations divided by ECEC and multiplied by 100% (Udo et al., 2009). Formular as follows;

$$Ca + Mg + K + Na / CEC \times 100$$

**Available Phosphorus:** Available phosphorus was determined by Brayp-1 extraction and p in the extraction was determined using Murphy and Riley methods as described by Udo et al., 2009).
## 2.6 Indices of Soil Physical Qualities

**Modified Clay Ratio (MCR) was Calculated Thus:** Modified clay ratio (MCR) was determined by summing up the percent of sand with percent of silt divided with the sum of percent of clay and percent of organic matter.

This was expressed as;

$$MCR = \frac{\% silt + \% sand}{\% clay + \% organic matter}$$

**Silt clay Ratio was Calculated Thus**

$$SCR = \frac{\text{Amount of sand} + \text{silt}}{\text{Clay}}$$

**Sodium Adsorption Ratio (SAR) Was Calculated Thus**

$$SAR = \frac{Na}{\sqrt{\frac{(CA + mg)}{2}}}$$

**Weight of Organic Matter Content was Calculated Thus**

$$\frac{\text{Weight of organic matter}}{\text{Weight of soil sample}} \times 100$$

## 2.7 Statistical Analysis

Data were summarized using descriptive statistics. Correlation analysis was used to determine the relationship between slope curvature and aspect with physical and chemical properties of the soil.

## 3. RESULTS AND DISCUSSION

### 3.1 Effect of Slope Characteristics on Soil Physical Properties Effect of Slope Aspect on Soil Physical Properties

The effects of slope aspects on some soil physical properties in the study area are presented in Table 1. The mean values of these properties serve as estimates of central tendency while the standard deviation (Std) and coefficient of varieties (cv) serve as measures of variability. The sand of NF slope ranges from 858 - 950 + 950 gkg⁻¹ with mean value of 917 ± 32.59 gkg⁻¹ (CV = 3.55%), while SF slopes ranges from 870 - 950 gkg⁻¹ with mean of 922 ± 21.40 gkg⁻¹ (CV = 2.32%). Sand being skeletal, with heavy rain, cause weak inter-particle attractive and cohesive forces (Ogban & Essien, 2016). The result shows that silt content ranges from, 6-48 gkg⁻¹ with NF slope had low mean value of 22 ± 16.88 gkg⁻¹ (CV = 75.59%), while silt in SF slope ranges from 6 - 48 with high mean value of 27 ± 13.97 gkg⁻¹ (CV = 50.20%). The results of the clay content showed that NF slope values ranges from 24 - 122 gkg⁻¹ with mean value of 59 ± 28.47 gkg⁻¹ (CV = 48.25%), while SF slope values ranges from 24 - 104 gkg⁻¹ mean value of 52.50 ± 19.76 gkg⁻¹ (CV = 37.64%). The high clay content in NF slope indicated that clay fraction being colloidal, highly reactive, cohesive and adhesive (Lal & Shukla, 2004). This may improve formation and stability of soil aggregate by providing the required bonding that will help bind the aggregate together and reduce soil erosion.

<table><caption>Table 1. Effect of slope aspect on soil physical properties</caption><thead><tr><th rowspan="2">S/N</th><th>Sand</th><th>Silt</th><th>Clay</th><th>Bd</th><th>Ksat</th><th>Tp</th></tr><tr><th>%</th><th>%</th><th>%</th><th>Mgm<sup>-3</sup></th><th>cmhr<sup>-1</sup></th><th>m<sup>3</sup>m<sup>-3</sup></th></tr></thead><tbody><tr><td colspan="7" style="text-align: center; font-weight: bold;">North</td></tr><tr><td>Minimum</td><td>858</td><td>6</td><td>24</td><td>1.28</td><td>1.69</td><td>0.44</td></tr><tr><td>Maximum</td><td>950</td><td>48</td><td>122</td><td>1.82</td><td>6.21</td><td>1.50</td></tr><tr><td>Mean</td><td>917</td><td>22.33</td><td>59</td><td>1.57</td><td>4.10</td><td>0.69</td></tr><tr><td>SD</td><td>32.59</td><td>16.88</td><td>28.47</td><td>0.20</td><td>1.54</td><td>0.29</td></tr><tr><td>CV (%)</td><td>3.55</td><td>75.59</td><td>48.25</td><td>12.74</td><td>37.56</td><td>42.03</td></tr><tr><td colspan="7" style="text-align: center; font-weight: bold;">South</td></tr><tr><td>Minimum</td><td>870</td><td>6</td><td>24</td><td>1.05</td><td>2.17</td><td>0.48</td></tr><tr><td>Maximum</td><td>950</td><td>48</td><td>104</td><td>2.22</td><td>5.88</td><td>2.01</td></tr><tr><td>Mean</td><td>922.33</td><td>27.83</td><td>52.50</td><td>1.61</td><td>3.65</td><td>0.76</td></tr><tr><td>SD</td><td>21.40</td><td>13.97</td><td>19.76</td><td>0.43</td><td>1.09</td><td>0.42</td></tr><tr><td>CV (%)</td><td>2.32</td><td>50.20</td><td>37.64</td><td>26.71</td><td>26.86</td><td>55.26</td></tr></tbody></table>

Bd = Bulk density, Ksat = saturated hydraulic conductivity Tp = total porosity
<table><caption>Table 2. Effect of slope curvature on soil physical properties</caption><thead><tr><th rowspan="2">S/N</th><th>Sand</th><th>Silt</th><th>Clay</th><th>Bd</th><th>Ksat</th><th>Tp</th></tr><tr><th>%</th><th>%</th><th>%</th><th>Mgm<sup>-3</sup></th><th>cmhr<sup>-1</sup></th><th>m<sup>3</sup>m<sup>-3</sup></th></tr></thead><tbody><tr><td colspan="7" style="text-align: center; font-weight: bold;">Concave</td></tr><tr><td>Minimum</td><td>870</td><td>6</td><td>42</td><td>1.12</td><td>2.17</td><td>0.55</td></tr><tr><td>Maximum</td><td>950</td><td>48</td><td>104</td><td>10.05</td><td>7.45</td><td>2.01</td></tr><tr><td>Mean</td><td>918.67</td><td>26</td><td>56</td><td>2.45</td><td>3.78</td><td>0.81</td></tr><tr><td>SD</td><td>22.42</td><td>15.04</td><td>17.37</td><td>2.41</td><td>1.72</td><td>0.40</td></tr><tr><td>CV (%)</td><td>2.44</td><td>57.85</td><td>31.01</td><td>98.37</td><td>45.50</td><td>49.38</td></tr><tr><td colspan="7" style="text-align: center; font-weight: bold;">Convex</td></tr><tr><td>Minimum</td><td>858</td><td>6</td><td>24</td><td>1.08</td><td>2.72</td><td>0.48</td></tr><tr><td>Maximum</td><td>950</td><td>46</td><td>122</td><td>2.29</td><td>5.88</td><td>1.50</td></tr><tr><td>Mean</td><td>919</td><td>20.67</td><td>58.83</td><td>1.52</td><td>4.14</td><td>0.68</td></tr><tr><td>SD</td><td>29.74</td><td>12.69</td><td>28.62</td><td>0.36</td><td>1.09</td><td>0.29</td></tr><tr><td>CV (%)</td><td>3.24</td><td>61.39</td><td>48.65</td><td>23.68</td><td>26.33</td><td>42.65</td></tr></tbody></table>

Bd = Bulk density, Ksat = saturated hydraulic conductivity Tp = total porosity

Effect of slope aspect on bulk density revealed that NF slope values ranges from 1.28 – 1.82 Mgm⁻³ with mean value of 1.61 ± 0.43 Mgm⁻³ (CV = 26.71%). The low bulk density was attributed to the high proportion of erosion activities along the slope. Saturated hydraulic conductivity results shows that NF slope values range from 1.69 – 6.21 cmhr⁻¹ with mean value of 4.10 ± 1.54 cmhr⁻¹ (CV = 37.56%), while SF slope ranges from 2.17 – 5.88 Mgm⁻³ with mean value of 3.65 ± 1.09 cmhr⁻¹ (CV = 26.86%). The result of high mean shows that fluid flow may not be impeded. Total porosity results indicated that NF slope values range from 0.44 – 1.50 m³m⁻³ low mean of 0.69 ± 0.29 m³m⁻³ (CV = 43.03%), while SF slope ranges from 0.48 – 2.01 m³m⁻³ with mean value of 0.76 ± 0.42 m³m⁻³ (CV = 55.26%). The results show that SF slope may experience severely impeded fluid flow which therefore reduces the rate of water flow.

## 3.2 Effect of Slope Curvature on Soil Physical Properties

The data generated from the sand content (Table 2) revealed that concave slope values ranges from 870 – 950 gkg⁻¹ with mean value of 919 ± 22.42 gkg⁻¹ (CV = 2.44%), while convex slope values ranges from 858 – 950 gkg⁻¹ with mean value of 919 ± 29.74 gkg⁻¹ (CV = 3.24%), convex had high variations in silt content and total result revealed that concave values range from 6 – 48 gkg⁻¹ with high mean value of 26 ± 15.04 gkg⁻¹ (CV = 57.85%), while convex slope value ranges from 6 – 48 gkg⁻¹ with high mean value of 20.67 ± 12.69 (CV = 61.39%). Clay content lower in concave slope ranges from 42 – 104 gkg⁻¹ with mean value of 56 ± 17.37gkg⁻¹ (CV = 31.01%), while convex slope values ranges from 24-122

gkg⁻¹ with high mean value of 58.83 ± 28.62 kg⁻¹ (CV = 48.65%). Having high clay will facilitate aggregation, due to their associated high cohesion and shear strength, in line with the work of Ogban and Essien, (2016).

The result of bulk density showed that concave slope value ranges from 1.12 – 10.95 Mgm⁻³, with 2.45 ± 2.41 Mgm⁻³ (CV = 98.37%), while convex slope ranges from 1.08 – 2.29 Mgm⁻³ with low of 1.52 ± 0.36 Mgm⁻³ (CV = 23.68%), bulk density in concave slope had high variability. Saturated hydraulic conductivity values ranges from 2.17 – 7.45, cmhr⁻¹ with mean value of concave slope was 3.78 ± 1.72 cmhr⁻¹ (CV = 45.50%), while convex slope ranges from 2.72 – 5.88 cmhr⁻¹ with mean value of 4.14 ± 1.09 cmhr⁻¹ (CV = 26.33%).

The total porosity result of concave slope showed that the values ranges from 0.55 – 2.01 m³m⁻³ with mean value of 0.81 ± 0.40 m³m⁻³ (CV = 49.83%), while convex slope ranges from 0.48 – 1.50 m³m⁻³ with mean value of 0.68 ± 0.29 m³m⁻³ (CV = 42.65%).

## 3.3 Effect of Characteristics on Soil Chemical Properties

**Effect of Slope Aspect on Soil Chemical Properties:** Effect of slope aspect on soil chemical properties are presented in Table 3.

The results of the effect of slope aspect on soil pH (H₂O) revealed that NF slope values ranges from 5.30 – 6.50 with mean value of 6.04 ± 0.34 (CV = 5.63%), while SF slope values ranges from 3.20 – 6.30% with mean value of 5.64 ± 0.85 (CV = 15.10%). Slope aspect affected
organic matter showed that, the values for MF Slope ranges from 2.50-3.80 %, with mean value of 3.37 ± 0.48 % (CV=14.26 %), while SF slope ranges from 2.00-6.80, with mean value of 3.90 ± 1.48 % (CV=37.95 %). The variation of organic matter content between land forms was related to differences in litter decomposition rates. SF slope receives sunlight that help in the decomposition of organic materials, while NF is in Contrast (Ogban and Essien, 2016). The low organic matter render the soils fragile under intense erosion. Available phosphorus values ranges from 1.50 - 14.47, with mean value of 5.22 ± 3.93 (CV=75.29 %), while SF values ranges from 2.50-9.20 with mean value of 5.81 ± 2.36 (CV = 40.62 %).

The results of Ca Showed that slope aspect affected Ca content, NF Slope Values ranges

from 0.82-10.00, with mean value of 2.82 ± 2.66 cmolkg⁻¹ (CV = 94.43%), While SF Slope ranges from 0.98-10.40, with mean value of 2.91 ± 51.16 cmolkg⁻¹ (CV= 287.90 %). Ca had high Variation.

The results of Mg Showed that NF slope Value ranges from 0.40-1.97 Cmol kg⁻¹ with mean value of 1.14 ± 0.51 Cmolkg⁻¹ (CV= 44.74%), while SF slope value ranges from 0.53 - 1.93 Cmolkg⁻¹, with mean value of 1.17 ± 0.49 Cmolkg⁻¹ (CV= 41.88 %). The result of K content revealed that values in NF.

Slope ranges from 0.13 - 0.48 Cmolkg⁻¹ with mean value of 0.30 ± 0.11 Cmolkg⁻¹ (CV = 36.67 %), while SF slope ranges from 0.17 - 0.49 cmolkg⁻¹, with mean value of 0.30 ± 0.10 Cmolkg⁻¹ (CV = 33.33 %).

<table><caption>Table 3. Effect of slope aspect on soil chemical properties</caption><thead><tr><th rowspan="2">S/N</th><th>Ph</th><th>OM</th><th>Av.P</th><th>Ca</th><th>Mg</th><th>K</th><th>Na</th><th>EA</th><th>ECE</th><th>Bsat</th></tr><tr><th>(H<sub>2</sub>O)</th><th>%</th><th>mgkg<sup>-1</sup></th><th colspan="6">C</th></tr><tr><th></th><th></th><th></th><th></th><th colspan="6">Cmol/ kg<sup>-1</sup></th></tr><tr><th></th><th></th><th></th><th></th><th colspan="6">%</th></tr></thead><tbody><tr><td>Minimum</td><td>5.30</td><td>2.53.</td><td>1.50</td><td>0.82</td><td>0.40</td><td>0.13</td><td>0.060.</td><td>1.608</td><td>5.181</td><td>26.80</td></tr><tr><td>maximum</td><td>6.50</td><td>380</td><td>14.47</td><td>10.00</td><td>1.97</td><td>0.48</td><td>80</td><td>.800</td><td>14.57</td><td>78.72</td></tr><tr><td>Mean</td><td>6.04</td><td>3.36</td><td>5.22</td><td>2.82</td><td>1.14</td><td>0.30</td><td>0.16</td><td>3.88</td><td>8.30</td><td>51.73</td></tr><tr><td>SD</td><td>0.34</td><td>0.48</td><td>3.93</td><td>2.66</td><td>0.51</td><td>0.11</td><td>0.20</td><td>1.57</td><td>2.75</td><td>15.33</td></tr><tr><td>CV (%)</td><td>5.63</td><td>1.40</td><td>75.29</td><td>94.43</td><td>44.74</td><td>36.6</td><td>125</td><td>40.46</td><td>33.13</td><td>29.63</td></tr><tr><td></td><td></td><td></td><td></td><td colspan="2">South</td><td colspan="4">Facing</td></tr><tr><td>Minimum</td><td>3.20</td><td>2.00</td><td>2.50</td><td>0.98</td><td>0.53</td><td>0.17</td><td>0.04</td><td>1.60</td><td>6.13</td><td>28.50</td></tr><tr><td>maximum</td><td>6.30</td><td>6.80</td><td>9.20</td><td>180.0</td><td>1.93</td><td>0.49</td><td>1.10</td><td>7.20</td><td>19.69</td><td>77.11</td></tr><tr><td>Mean</td><td>5.64</td><td>3.90</td><td>5.81</td><td>17.77</td><td>1.17</td><td>0.30</td><td>0.38</td><td>5.04</td><td>9.50</td><td>47.69</td></tr><tr><td>SD</td><td>0.85</td><td>1.48</td><td>2.36</td><td>51.16</td><td>0.49</td><td>0.10</td><td>0.43</td><td>1.94</td><td>3.60</td><td>16.00</td></tr><tr><td>CV (%)</td><td>15.10</td><td>37.95</td><td>40.62</td><td>287.90</td><td>41.88</td><td>33.33</td><td>113.16</td><td>38.49</td><td>37.89</td><td>33.55</td></tr></tbody></table>

OM = Organic matter, Av.P = Available phosphorus, Ca = Calcium, Mg = Magnesium, K = Potassium, Na = Sodium, EA = Exchangeable acidity, ECEC = Effective cation exchange capacity, Bsat = Base saturation

<table><caption>Table 4. Effect of slope curvature on soil chemical properties</caption><thead><tr><th rowspan="2">pH</th><th rowspan="2">OM</th><th rowspan="2">Av.P</th><th rowspan="2">Ca</th><th rowspan="2">Mg</th><th rowspan="2">K</th><th rowspan="2">Na</th><th rowspan="2">EA</th><th rowspan="2">ECEC</th><th rowspan="2">Bsat</th></tr><tr><th colspan="6">Cmol/ kg<sup>-1</sup></th></tr><tr><th>(H<sub>2</sub>O)</th><th>%</th><th colspan="2">mgkg<sup>-1</sup></th><th colspan="6">%</th></tr><tr><th></th><th></th><th>Con</th><th>Cave</th><th colspan="6">Slope</th></tr></thead><tbody><tr><td>Minimum</td><td>4.90</td><td>2.00</td><td>1.87</td><td>0.98</td><td>0.40</td><td>0.04</td><td>0.04</td><td>1.60</td><td>6.08</td><td>27.27</td></tr><tr><td>maximum</td><td>6.30</td><td>6.80</td><td>14.47</td><td>5.60</td><td>1.97</td><td>0.49</td><td>0.80</td><td>6.40</td><td>11.14</td><td>73.68</td></tr><tr><td>Mean</td><td>5.97</td><td>3.70</td><td>6.30</td><td>2.44</td><td>1.04</td><td>0.26</td><td>0.16</td><td>4.16</td><td>7.98</td><td>49.28</td></tr><tr><td>SD</td><td>0.40</td><td>1.56</td><td>3.61</td><td>1.62</td><td>0.55</td><td>0.13</td><td>0.21</td><td>1.47</td><td>1.56</td><td>14.04</td></tr><tr><td>CV (%)</td><td>6.70</td><td>42.16</td><td>57.30</td><td>66.39</td><td>52.88</td><td>50</td><td>131.25</td><td>35.34</td><td>19.55</td><td>28.49</td></tr><tr><td></td><td></td><td>Con</td><td>Vex</td><td colspan="6">Slope</td></tr><tr><td>Minimum</td><td>3.20</td><td>2.30</td><td>1.50</td><td>1.01</td><td>0.40</td><td>0.18</td><td>0.06</td><td>1.60</td><td>5.94</td><td>26.80</td></tr><tr><td>maximum</td><td>6.40</td><td>4.30</td><td>7.47</td><td>10.40</td><td>1.93</td><td>0.48</td><td>0.80</td><td>8.00</td><td>19.69</td><td>78.72</td></tr><tr><td>Mean</td><td>5.72</td><td>3.33</td><td>4.06</td><td>3.72</td><td>1.19</td><td>0.32</td><td>0.21</td><td>5.09</td><td>10.48</td><td>50.30</td></tr><tr><td>SD</td><td>0.85</td><td>0.60</td><td>2.03</td><td>3.33</td><td>0.45</td><td>0.09</td><td>0.28</td><td>2.07</td><td>3.71</td><td>18.50</td></tr><tr><td>CV (%)</td><td>14.86</td><td>18.02</td><td>50</td><td>89.52</td><td>37.82</td><td>28.13</td><td>133.33</td><td>40.67</td><td>35.40</td><td>36.78</td></tr></tbody></table>

OM = Organic matter, Av.P = Available phosphorus, Ca = Calcium, Mg = Magnesium, K = Potassium, Na = Sodium, EA = Exchangeable acidity, ECEC = Effective cation exchange capacity, Bsat = Base saturation
Na result revealed that NF slope ranges from 0.06 - 0.80 Cmolkg⁻¹, with mean value of 0.16 ± 0.20 Cmolkg⁻¹ (CV = 125 %), while SF slope ranges from 0.04 - 1.10 Cmolkg⁻¹ (CV = 113.16 %). EA result revealed that NF slope ranges from 1.60 - 8.00 Cmolkg⁻¹ with mean value of 3.88 ± 1.57 Cmolkg⁻¹ (CV = 40.46 %), while SF slope ranges from 1.60 - 7.20 Cmolkg⁻¹, with mean value of 5.04 ± 1.94 Cmolkg⁻¹ (CV = 38.49 %).

ECEC content of NF slope values ranges from 5.18 - 14.57 cmolkg⁻¹, with mean value of 8.30 ± 2.75 Cmolkg⁻¹ (CV = 33.13 %), While SF slope ranges from 6.13 - 19.69 Cmolkg⁻¹, with mean value of 9.5 ± 3.60 Cmolkg⁻¹ (CV = 37.89 Cmolkg⁻¹).

Bsat result indicated that NF slope values ranges from 26.80 - 78.72 % with mean value of 51.73 ± 15.33 % (CV = 29.63 %), While SF slope ranges from 28.50 - 77.11 %, with mean value of 47.69 ± 16.00 % (CV = 33.55 %). Bsat Saturation obtained revealed that NF slope recorded high mean value. Base saturation is used in classifying the fertility level of soils with values greater or lower than 50 % indicating fertile or low fertility soils, respectively (FAO, 1998). However, the high Bsat in the NF slope could best explain in terms of the proportion of TEB and the ECEC of the respective soils.

**Effects of Slope Curvature on Soil Chemical Properties:** The results of effects of slopes curvature in Table 4, indicated that concave slopes, pH ranges from 4.90 - 6.30, with mean value 5.97 ± 0.40 (CV = 6.70 %), while convex slope ranges from 3.20 - 6.40, with mean value of 5.72 ± 0.85 (CV = 14.86 %). Om results revealed that concave slope values ranges from 2.00 - 6.80 %, with mean value of 3.70 ± 1.56 % (CV = 42.16 %), while convex slope ranges from 2.30-4.30 %, with mean value of 3.33 ± 0.60 % (CV = 18.02 %). Available Phosphorus values ranges from 1.87 - 14.47 with mean value of 6.30 ± 3.61 (CV = 57.30 %), while Convex slope ranges from 1.50-7.47, with mean value of 4.06 ± 2.03 (CV = 50%).

Ca result revealed that concave slope values ranges from 0.98-5.60 Cmolkg⁻¹, with mean value of 2.44 ± 1.62 Cmolkg⁻¹ (CV = 66.39 %), While convex slope ranges from 1.01 - 10.40 Cmolkg⁻¹, with mean value of 3.72 ± 3.33 cmolkg⁻¹ (CV = 89.52 %). Mg result indicated that concave slope ranges from 0.40 - 1.97 Cmolkg⁻¹ with mean value of 1.04 ± 0.55 Cmolkg⁻¹ (CV = 52.88%) while convex slope ranges from 0.40

- 1.93 Cmolkg⁻¹ with mean value of 1.19 ± 0.45 Cmolkg⁻¹ (CV = 37.82 %).

K result indicated that K content in concave slope 0.49 Cmolkg⁻¹, with mean value of 0.26 ± 0.13 Cmolkg⁻¹ (CV = 50 %), while convex slope ranges from 0.18 - 0.48 Cmolkg⁻¹ with mean value of 0.32 ± 0.09 Cmolkg⁻¹ (CV = 28.13 %).

Na result showed that concave slope values ranges from 0.04 - 0.80 Cmolkg⁻¹, with mean value of 0.16 ± 0.21 Cmolkg⁻¹ (CV = 131.25 %), while convex slope ranges from 0.06 - 0.80 Cmolkg⁻¹ with mean value of 0.21 ± 0.28 Cmolkg⁻¹ (CV = 133.33 %). Na had high variability among the chemical properties of the soil in the study area.

EA showed result values, ranges from 1.60 - 6.40 C molkg⁻¹ concave slope, while convex slope value ranges from 1.60 - 8.00 Cmolkg⁻¹ with mean value of 5.09 ± 2.07 Cmolkg⁻¹ (CV = 40.67 %). The result of ECEC under concave slope, values ranges from 6.08 - 11.14 Cmolkg⁻¹ with mean value of 7.98 ± 1.56 C molkg⁻¹ (CV = 19.55 %), while convex slope values ranges from 5.94 - 19.69 Cmolkg⁻¹ with mean value of 10.48 ± 3.71 Cmolkg⁻¹ (CV = 35.40 %).

Bsat result revealed that concave slope values ranges from 27.27 - 73.68 %, with mean value of 49.28 ± 14.04 % (CV = 28.49 %), while convex slope value ranges from 26.80 - 78.72 %, with high mean value of 50.30 ± 18.50 % (CV = 36.78 %).

## 3.4 Effect of Slope Characteristics on Soil Quality indices

**Effect of Slope Aspect on Indices of Soil Quality:** The result of slope aspect on soil quality indices (Table 5) revealed that NF Slope values in SCR ranges from 2.07 - 79.10, with mean value of 19.59 ± 20.05 (CV = 102.35 %), while SF Slope IN SCR ranges from 8.61 - 40.60, with mean value of 20.34 ± 7.71 (CV = 37.91 %). SAR result indicated that NF slope values ranges from 0.40 - 0.75, with mean value of 0.18 ± 0.19 (CV = 105.55 %), while SF ranges from 0.01 - 2.85, with mean value of 0.46 ± 0.83 (CV = 180.43 %). WOM result showed that NF slope values ranges from 500-760, with mean value of 673 ± 95.91 (CV = 14.24 %), while SF slope ranges from 400 - 1360, with mean value of 780 ± 296.53 (CV = 38.02 %). MCR result indicated that NF slope values ranges from 6.67-35.60, with mean value of 17.65 ± 7.25 (CV = 43.34 %).
<table><caption>Table 5. Effect of slope aspect on indices of soil quality</caption><thead><tr><th rowspan="2">S/N</th><th>SCR</th><th>SAR</th><th>WOM</th><th>MCR</th></tr><tr><th>North</th><th>facing</th><th>Slope</th><th></th></tr></thead><tbody><tr><td>Minimum</td><td>2.07</td><td>0.04</td><td>500</td><td>6.97</td></tr><tr><td>Maximum</td><td>79.10</td><td>0.75</td><td>760</td><td>35.60</td></tr><tr><td>Mean</td><td>19.59</td><td>0.18</td><td>673.33</td><td>17.65</td></tr><tr><td>SD</td><td>20.05</td><td>0.19</td><td>95.91</td><td>7.25</td></tr><tr><td>CV (%)</td><td>102.35</td><td>105.55</td><td>14.24</td><td>43.34</td></tr><tr><td></td><th>South</th><th>Facing</th><th>Slope</th><th></th></tr><tr><td>Minimum</td><td>8.61</td><td>0.01</td><td>400</td><td>8.31</td></tr><tr><td>Maximum</td><td>40.60</td><td>2.85</td><td>1360</td><td>164.80</td></tr><tr><td>Mean</td><td>20.34</td><td>0.46</td><td>780</td><td>30.78</td></tr><tr><td>SD</td><td>7.71</td><td>0.83</td><td>296.53</td><td>42.67</td></tr><tr><td>CV (%)</td><td>37.91</td><td>180.43</td><td>38.02</td><td>138.63</td></tr></tbody></table>

$$ \begin{aligned} \text{SCR} &= \text{Silt clay ratio}, \quad \text{SAR} = \text{Sodium absorption ratio}, \quad \text{WOM} = \text{Weight of organic matter}, \quad \text{MCR} \\ &= \text{Modified clay ratio} \end{aligned} $$

<table><caption>Table 6. Effect of slope curvature on indices of soil quality</caption><thead><tr><th rowspan="2">S/N</th><th>SCR</th><th>SAR</th><th>WOM</th><th>MCR</th></tr><tr><th>Concave</th><th>Slope</th><th></th><th></th></tr></thead><tbody><tr><td>Minimum</td><td>8.61</td><td>0.04</td><td>400</td><td>4</td></tr><tr><td>Maximum</td><td>22.80</td><td>1.02</td><td>1360</td><td>20.70</td></tr><tr><td>Mean</td><td>18.02</td><td>0.20</td><td>739.33</td><td>15.94</td></tr><tr><td>SD</td><td>4.31</td><td>0.27</td><td>311.14</td><td>5.30</td></tr><tr><td>CV (%)</td><td>23.92</td><td>135</td><td>42.08</td><td>33.25</td></tr><tr><td></td><th>Convex</th><th>Slope</th><th></th><th></th></tr><tr><td>Minimum</td><td>0.13</td><td>0.04</td><td>460</td><td>6.97</td></tr><tr><td>Maximum</td><td>40.60</td><td>13.30</td><td>860</td><td>34.40</td></tr><tr><td>Mean</td><td>18.55</td><td>1.20</td><td>66.667</td><td>17.70</td></tr><tr><td>SD</td><td>9.545</td><td>3.81</td><td>119.19</td><td>7.02</td></tr><tr><td>CV (%)</td><td>51.45</td><td>317.5</td><td>178.78</td><td>39.66</td></tr></tbody></table>

<table><caption>Table 7. Correlation matrix among physical properties and indices of soil quality at North Facing Slope</caption><thead><tr><th></th><th>Sand</th><th>Silt</th><th>Clay</th><th>Bd</th><th>Ksat</th><th>Tp</th><th>SCR</th><th>SAR</th><th>WOM</th><th>MCR</th></tr></thead><tbody><tr><td>Sand</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Silt</td><td>-0.487</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Clay</td><td>-0.842**</td><td>-0.026</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Bd</td><td>0.165</td><td>0.603*</td><td>-0.575</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Ksat</td><td>0.403</td><td>-0.591*</td><td>-0.168</td><td>-0.317</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Tp</td><td>063.1</td><td>-0.101</td><td>-0.103</td><td>-0.180</td><td>-0.141</td><td>1.000</td><td></td><td></td><td></td><td></td></tr><tr><td>SCR</td><td>0.358</td><td>-0.332</td><td>-0.210</td><td>0.206</td><td>-0.229</td><td>-0.047</td><td>1.000</td><td></td><td></td><td></td></tr><tr><td>SAR</td><td>-0.031</td><td>-0.109</td><td>-0.093</td><td>0.130</td><td>0.434</td><td>-0.187</td><td>-0.149</td><td>1.000</td><td></td><td></td></tr><tr><td>WOM</td><td>0.091</td><td>-0.277</td><td>0.176</td><td>-0.125</td><td>-0.023</td><td>0.229</td><td>0.276</td><td>-0.480</td><td>1.000</td><td></td></tr><tr><td>MCR</td><td>0.683*</td><td>0.138</td><td>0.864**</td><td>0.472</td><td>0.247</td><td>-0.048</td><td>0.004</td><td>0.036</td><td>-0.077</td><td>1.000</td></tr></tbody></table>

*Correlation significantly at P ≤ 5%

** Correlation significantly at P ≤ 1%

**Effect of Slope Curvature on Indices of Soil Quality:** The result of slope curvature on indices of soil quality (Table 6) indicated that concave slope under SCR values ranges from 8.61 - 22.80, with mean value of 18.02 ± 4.31 (CV = 23.92 %), while convex slope ranges from 0.13 -

40.60, with mean value of 18.55 ± 9.55 (CV = 51.45 %). Concave slope shows that SAR value ranges from 0.04 - 1.02 with mean value of 0.20 ± 0.27 (CV = 135 %), while convex slope, SAR values ranges from 0.04 - 13.30, with mean value of 1.20 ±3.81 (CV = 317.5 %).
<table><caption>Table 8. Correlation matrix of soil physical properties with indices of soil quality in South Facing Slope</caption><thead><tr><th></th><th>Sand</th><th>Silt</th><th>Clay</th><th>Bd</th><th>Ksat</th><th>Tp</th><th>SCR</th><th>SAR</th><th>WOM</th><th>MCR</th></tr></thead><tbody><tr><td>Sand</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Silt</td><td>-0.491</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Clay</td><td>-0.674*</td><td>-0.230</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Bd</td><td>-0.405</td><td>0.081</td><td>0.296</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Ksat</td><td>-0.330</td><td>0.517</td><td>0.036</td><td>-0.353</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Tp</td><td>-0.106</td><td>0.030</td><td>0.172</td><td>0.352</td><td>-0.275</td><td>1.000</td><td></td><td></td><td></td><td></td></tr><tr><td>SCR</td><td>0.430</td><td>0.382</td><td>-0.858**</td><td>-0.261</td><td>0.344</td><td>-0.216</td><td>1.000</td><td></td><td></td><td></td></tr><tr><td>SAR</td><td>-0.006</td><td>0.150</td><td>-0.119</td><td>-0.441</td><td>0.388</td><td>-0.223</td><td>0.003</td><td>1.000</td><td></td><td></td></tr><tr><td>WOM</td><td>-0.229</td><td>0.340</td><td>0.023</td><td>0.104</td><td>-0.094</td><td>0.592*</td><td>0.014</td><td>-0.444</td><td>1.000</td><td></td></tr><tr><td>MCR</td><td>0.182</td><td>0.009</td><td>-0.264</td><td>-0.445</td><td>-0.095</td><td>-0.071</td><td>0.202</td><td>-0.148</td><td>0.598*</td><td>1.000</td></tr></tbody></table>

<table><caption>Table 9. Correlation matrix of soil physical properties with indices of soil quality in Concave Slope</caption><thead><tr><th></th><th>Sand</th><th>Silt</th><th>Clay</th><th>Bd</th><th>Ksat</th><th>Tp</th><th>SCR</th><th>SAR</th><th>WOM</th><th>MCR</th></tr></thead><tbody><tr><td>Sand</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Silt</td><td>-0.638*</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Clay</td><td>-0.739**</td><td>-0.036</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Bd</td><td>0.134</td><td>-0.021</td><td>-0.165</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Ksat</td><td>-0.028</td><td>0.046</td><td>-0.023</td><td>-0.157</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Tp</td><td>-0.023</td><td>-0.014</td><td>0.169</td><td>-0.042</td><td>-0.170</td><td>1.000</td><td></td><td></td><td></td><td></td></tr><tr><td>SCR</td><td>0.662*</td><td>0.085</td><td>0.955**</td><td>0.212</td><td>0.119</td><td>-0.274</td><td>1.000</td><td></td><td></td><td></td></tr><tr><td>SAR</td><td>-0.025</td><td>0.325</td><td>-0.267</td><td>-0.272</td><td>0.515</td><td>-0.227</td><td>0.340</td><td>1.000</td><td></td><td></td></tr><tr><td>WOM</td><td>-0.020</td><td>0.101</td><td>0.011</td><td>0.655*</td><td>-0.212</td><td>0.567</td><td>0.000</td><td>-0.366</td><td>1.000</td><td></td></tr><tr><td>MCR</td><td>0.550</td><td>0.047</td><td>0.768**</td><td>0.120</td><td>0.121</td><td>-0.285</td><td>0.853**</td><td>0.338</td><td>0.002</td><td>1.000</td></tr></tbody></table>

<footnote>*correlation significantly at P ≤ 5%</footnote>

<footnote>** Correlation significantly at P ≤ 1%</footnote>

<footnote>*correlation significantly at P ≤ 5%</footnote>

<footnote>** Correlation significantly at P ≤ 1%</footnote>
<table><caption>Table 10. Correlation matrix of soil physical properties with indices of soil quality in Convex Slope</caption><thead><tr><th></th><th>Sand</th><th>Silt</th><th>Clay</th><th>Bd</th><th>Ksat</th><th>Tp</th><th>SCR</th><th>SAR</th><th>WOM</th><th>MCR</th></tr></thead><tbody><tr><td>Sand</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Silt</td><td>-0.303</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Clay</td><td>0.866**</td><td>-0.155</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Bd</td><td>0.123</td><td>0.290</td><td>-0.290</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Ksat</td><td>0.100</td><td>-0.028</td><td>-0.145</td><td>-0.294</td><td>1.000</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Tp</td><td>0.338</td><td>-0.250</td><td>-0.216</td><td>0.122</td><td>-0.091</td><td>1.000</td><td></td><td></td><td></td><td></td></tr><tr><td>SCR</td><td>0.679*</td><td>0.408</td><td>0.898**</td><td>0.173</td><td>0.317</td><td>0.168</td><td>1.000</td><td></td><td></td><td></td></tr><tr><td>SAR</td><td>-0.094</td><td>-0.021</td><td>-0.096</td><td>0.119</td><td>0.383</td><td>-0.114</td><td>-0.001</td><td>1.000</td><td></td><td></td></tr><tr><td>WOM</td><td>-0.220</td><td>0.499</td><td>0.069</td><td>0.325</td><td>0.014</td><td>0.263</td><td>0.175</td><td>-0.444</td><td>1.000</td><td></td></tr><tr><td>MCR</td><td>0.691*</td><td>0.340</td><td>0.883**</td><td>0.157</td><td>0.358</td><td>0.148</td><td>0.986**</td><td>-0.002</td><td>0.197</td><td>1.000</td></tr></tbody></table>

WOM values under concave slope ranges from 400-1360 with mean value of 739 ± 311.14 (CV = 42.08 %), while convex slope ranges from 460-860 with mean value of 67 ± 119.19 (CV = 178.78 %).

Concave slope showed that MCR values ranges from 4 -20.70, with mean value of 15.94 ± 5.30 (CV = 33.25 %), while convex slope ranges from 6.97 - 34.40, with mean value of 17.70 ± 7.02 (CV = 39.66 %).

## 3.5 Correlation Matrix among Physical Properties and Indices of Soil Quality under Slope Aspect

In NF slope, the result in Table 7 shows that sand correlated negatively with clay (r=- 0.842**) at 1 % and positively with MCR (0.683) at 5%, while in SF slope (Table 8) sand positively correlated negatively (-0.6714) at 5 %. The positive correlation between sand and MCR indicated that MCR may improve soil cohesion and absorption capacity of the soil. In NF, silt correlated positively with Bd (0.603) 5 % negatively with ksat (-0.591) at 5 %. The negative correlation indicated that silt content may sealed up the pore space and reduce flow of water. There was no relationship among silt with soil properties in the SF. In NF, clay correlated negatively with MCR (-0.864) at 1 % and negatively with SCR (-0.858) at 1 %. Tp correlated positively with WOM in SF slope (0.592) at 5 %. WOM correlated positively with MCR (0.598) at 5 % in SF slope.

## 3.6 Correlation Matrix among Physical Properties and Indices of Soil Quality under Slope Curvature

The result of the relationship between soil physical properties and indices of soil quality

under slope curvature (Tables 9 and 10) showed that, under concave slope, sand correlated negatively with silt and clay and positively with SCR (-0.638, - 0.739 and 0.662), respectively. In convex slope sand negatively with correlated with clay and positively with SCR and MCR (r=- 0.866**, r=0.679* and r = 0.691), respectively. In concave slope, clay correlated negatively with SCR and MCR r = 0.955** and - r = 0.768**) respectively. In convex, clay correlated negatively with SCR and MCR (r=- 0.898** and r=-0.883**) respectively. In concave slope Bd correlated positively with WOM (r = 0.655). SCR in concave correlated positive with MCR (r = 0.853) and MCR (r = 0.986) in convex slope.

## 4. SUMMARY AND CONCLUSION

This study investigated the impact of slope curvature and aspect on soil physical and chemical properties, as well as soil quality indices. The results indicated significant variations in these properties across different slope characteristics. North-facing slopes generally exhibited lower sand content but higher clay and bulk density compared to south-facing slopes. Concave slopes tended to have higher sand content and bulk density, while convex slopes showed higher silt content and hydraulic conductivity. Chemical properties also varied significantly across slope aspects and curvatures. North-facing slopes typically had lower pH but higher organic matter content compared to south-facing slopes. Concave slopes showed higher available phosphorus and exchangeable acidity, while convex slopes had higher calcium and base saturation. Soil quality indices such as silt-clay ratio, sodium absorption rate, wet organic matter, and modified clay ratio differed among slope aspects and curvatures,

<footnote>*correlation significantly at P ≤ 5%</footnote>

<footnote>** Correlation significantly at P ≤ 1%</footnote>
indicating variations in soil texture, fertility, and water retention. The study highlighted strong positive relationships between silt-clay ratio and modified clay ratio, as well as between sodium absorption rate and hydraulic conductivity. Moderate positive correlations were observed between silt content and wet organic matter, and between hydraulic conductivity and total porosity. Overall, the findings emphasize the importance of considering slope characteristics in agricultural and environmental management strategies to optimize soil health and productivity. Implementing site-specific soil management practices, such as contour plowing, terracing, and cover cropping, can help mitigate soil erosion and improve soil structure. Targeted fertilization and soil amendment strategies can also address nutrient deficiencies and enhance soil fertility. Further interdisciplinary research is recommended to explore the long-term effects of slope characteristics on soil properties and ecosystem sustainability.

## DISCLAIMER (ARTIFICIAL INTELLIGENCE)

Author(s) hereby declare that generative AI technologies such as Large Language Models, etc have been used during writing or editing of this manuscript. This explanation will include the name, version, model, and source of the generative AI technology and as well as all input prompts provided to the generative AI technology.

## COMPETING INTERESTS

Authors have declared that no competing interests exist.

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