





























1 

 

In ternationa l
Scholars
Journa ls

 

African Journal of Pig Farming ISSN: 2375-0731 Vol. 10 (3), pp. 001-010, March, 2022. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 
 
 
Full Length Research Paper                   

Shea waste slurry as an organic soil amendment of 
tropical soils in the Tamale Metropolis, Northern Ghana 

 
Abagale F. K.*, Alazuga I. N. A. and Osei A. R. 

 
School of Engineering, University for Development Studies, Tamale, Ghana. *Corresponding author E-mail: 

fabagale@uds.edu.gh. 
 

Accepted 21 June, 2021  
 

Infertile and less productive soil due to continuous cropping, poor soil management and other forms of 
land exploitation are mostly amended using inorganic fertiliser. Shea waste slurry (SWS) as an organic 
soil amendment material was applied to soils in two locations and its effect on plant primary and 
secondary nutrients evaluated. One-way diagonal method was employed in sampling soil from fields 
measuring 25 m×40 m at depths of 0-30 and 30-60 cm for SWS applied and non-applied soils. Results 
showed increased pH resulting from SWS application and EC increasing from 41.15±3.89 to 155.5±83.4 
µS/cm in both locations. SWS application also increased %N levels at depth of 0-30 cm from 0.03±0.0 to 
0.56±0.2%, concentration of P increased from 3.47±0.62 to 262.0±176 mg/kg and K from 21.9±2.39 to 
231.6±98 mg/kg. Na levels increased from a low of 0.46±0.09 to a maximum of 2.81±1.0 meq/100 g in 
both study sites, Mg increased from 0.80±0.3 to 8.51±4.86 meq/100 g whilst Ca increased from 1.6±0.07 
to 6.3±098 meq/100 g for the depth of 0-30 cm. Soil %OM and OC, respectively increased from 0.58±0.01 
to 10.94±3.95 and 0.34±0.11 to 6.36 ±2.29% for the depth of 0 to 30 cm in both study locations. The study 
indicated a general increase in the levels of all the parameters analysed for the study at the SWS 
applied soils as compared to the non-applied soils. The use of SWS as a soil nutrient amendment in 
crop production as an organic material was observed to be very effective. 

 
Key words: Shea waste slurry (SWS), organic soil amendment, tropical soil, plant nutrients.  

 
 
INTRODUCTION 

 
The success of soil management to maintain soil quality 
depends on the understanding of how soils respond to 
agricultural use and practices over time (Negassa and 
Gebrekidan, 2004). Ayoola (2006) reported improvement 
of environmental conditions and public health as well as 
the need to reduce costs of fertilising crops to also be 
important reasons for advocating increased use of 
organic materials. Excessive and inappropriate use of 
chemical fertilisers has been reported by different authors 
as a major cause of nutrient imbalance and degrading  

 
 
 
 

 
soils (Singh and Agarwal, 2001; Meena et al., 2003; 
Mahajan et al., 2008; Mukhtar et al., 2011).  

According to Tran-Thi et al. (2004), among available 
means to achieve sustainability in agricultural production, 
organic manure and bio-fertiliser play an important and 
key role because they possess many desirable soil 
properties and exert beneficial effect on soil physical, 
chemical and biological characteristics. Crop yield 
increased from 30 to 50% resulting from application of 
commercial fertilisers as indicated by Vlek (1990) and  
   

  



2 

 

 
 
 

 

Stewart et al. (2005).  
Shea butter is a product from the nuts of the Shea tree 

(Vitellaria paradoxa) mainly found in the savannah region 
of West Africa. The butter is used for domestic 
consumption (mainly as edible oil) and in some products 
of the cosmetic and pharmaceutical industries (Cof, 2016; 
Akparanta et al., 2017).  

The Shea butter processing industry is an increasing 
economic venture which serves as the principal source of 
income, particularly for many women in northern Ghana 
(Jibreel et al., 2013).  

According to Teketay et al. (2003), processing of the 
Shea butter from the Shea fruit is labour-intensive activity 
mainly carried out using traditional techniques by women. 
The basic processes for the butter extraction begin with 
the collection of nuts, de-pulping, drying of nuts, 
dehusking, drying and smoking of kernels and pounding 
and grinding into past. Next is mixing with water, treading, 
kneading and churning, floating and refining, solidifying 
and moulding (Teketay et al., 2003). The tradition 
processing method generates significant quantities of 
both liquid and solid waste which is described by Jibreel 
et al. (2013) as brown water and black sludge. The liquid 
fraction, according to Ofosu (2009), constitutes 
suspended and dissolved OM and oil, which might have a 
potential impact on the environment.  

Shea waste-slurry (SWS) as used in this study refers to 
the concentration of the remnant liquid (brown water) and 
solid (black sludge) as well as the oil at the end of the 
Shea butter extraction processes (Abagale et al., 2012). It 
is generally disposed of into the surroundings in the 
production communities which accumulate onto receiving 
soils. A survey conducted by Jibreel et al. (2013) in the 
Tamale metropolis realised that the solid waste-slurry is 
dried into cake for further use while almost 46% of the 
Shea butter processors disposed of the liquid waste on 
bare land.  

Production of Shea waste-slurry is thus expected to 
increase as small-scale Shea butter processing industries 
continues to gain much attention as a potential economic 
venture in the Tamale Metropolis.  

Organic waste generally has a significant effect on soil 
properties (physical, chemical, and biological) which 
favours plant growth and development (Hossain et al., 
2017). According to Jibreel et al. (2013), the intrinsic 
elements in waste-slurry might alter the structure and 
properties of receiving soils and affect crop development 
(Jibreel et al., 2013). A study by Abagale et al. (2012) 
highlighted the positive potentials of Shea waste-slurry on 
improving soil physical properties such as the bulk 
density, infiltration rate, porosity, gravimetric and 
volumetric moisture content for crop development in 
northern Ghana. However, the fertiliser potentials of SWS 
for the recycling of essential plant nutrients, has over the 
years receive little attention (Danikuu, 2016).  

The study, therefore, examined the effect of SWS as an 
organic soil amendment material for enhancing soil 

 
 

  
 
 

 

nutrients for the small-scale subsistence farmer. 
 

 
MATERIALS AND METHODS 
 
Study area 
 
The study was conducted in two communities: Kasaligu and 

Jisonayilli in the Tamale Metropolis (731 km
2
) and located on 

latitude 9°24′30.10″N and longitude 0°50′25.63″W of northern 
Ghana.  

The northern region of Ghana is characterised by a unimodal 
rainfall pattern with an average annual rainfall of 1,000 to 1,300 mm 
which begins from May to October with the peak occurring between 
August and September. A long dry period is experienced between 
the months of November and May. The region is one of the hottest 
in the country with an annual average temperature of 29 to 34°C. 
Reference evapotranspiration (ETo) is reported above 600 mm/year 
(Kranjac-Berisavljevic, 1999; Armah et al., 2010; Abdul-Ganiyu, 
2011).  

Soils in the study areas are mostly sandstone, mudstone and 
shale and these have weathered into different soil grades. Due to 
seasonal erosion, soils emanating from this phenomenon are sand, 
clay and laterite oxysols. The parent rock of the experimental field 
consists of sandstone and clay-shale and belongs to rock of the 
abosum bed of the lower voltaian formation. The soil belongs to 
Kpalsawgu series and consists of yellow-brown clay and silt which 
are developed mainly from local colluvium (SARI, 1993). 

 

Soil sampling and analysis 
 
The study was carried out on soils that are used for the disposal of 
Shea waste-slurry and cultivated for small-scale subsistence 
farming in the selected communities. These soils are manually tilled 
with simple farm tools (hoe and cutlass) at the onset of the raining 
season for the production of grains, cereals and vegetables. Typical 
crops include Capsicum annuum (pepper), Zea mays (maise) and 
Pennisetum glaucum (millet).  

The study considered soils with SWS as the treatments while 
adjacent soils without the SWS were used for the control. One-way 
diagonal method was employed in soil sampling towards the ends 
of the 25 m × 40 m diagonal fields for both sites of application of 
SWS and non-application of SWS as control.  

Soil samples were taken uphill of about 200 m away from the 
application site of SWS against gradient in each of the study areas 
to avoid interference from the application site. 200 g of soil samples 
were taken from 0-30 and 30-60 cm depths at both applied and 
non-applied sites of SWS. Sampling was carried out during the dry 
season before land cultivation. A total of 16 samples of soil were 
collected from the sampling sites for laboratory analysis. The GPS 
coordinates of the various sampling points and the standard 
methods of laboratory analysis are presented in Tables 1 and 2 
respectively 

 

Data analysis 
 
The analysis was carried out to determine and compared the 
concentration of the selected parameters for the different sampling 
sites (treatment and control) with respect to the depth (0-30 and 30-
60 cm). The variation in soil nutrients as influenced by SWS was 
analysed using Analysis of Variance (ANOVA) at probability (p) of 
<0.05. Means at the various sites were compared for significant 
difference using the Fisher Pairwise Comparisons (LSD) method at 
95% confidence interval. Data were analysed using Minitab 17 and 
GraphPad prism 8. 



3 

 

 
 
 
 

 
Table 1. Geo-references of soil sampling points.  

 
 Site Latitude (º) Longitude (º) Altitude (m) 

 KAD1 N 09.40517 W 000.92334 169 

 KAD2 N 09.40142 W 000.92448 166 

 KAN1 N 09.40344 W 000.92555 163 

 KAN2 N 09.40545 W 000.92452 167 

 JID1 N 09.45208 W 000.85558 163 

 JID2 N 09.45307 W 000.85557 165 

 JIN1 N 09.45342 W 000.85529 168 

 JIN2 N 09.45333 W 000.85629 167 
 

KAD = Kasalgu Applied Site; KAN = Kasalgu Non-Applied Site; JID = Jisonayilli Applied Site, JIN 
= Jisonayilli Non-Applied Site. 

 
 

 
Table 2. Laboratory methods of soil samples.  
 
 Soil parameter Analysis method Reference 

 Soil pH Supernatant suspension of a 1:2.5 soil to water ratio using pH meter Rhoades (1982) 

 Electrical conductivity (EC) 1:2.5 soil to water suspension was measured using Conductivity Meter Motsara and Roy (2008) 

 Organic carbon (OC) Walkley-Black method Walkley and Black (1934) 

 Organic matter (OM) Wet combustion with K2Cr2O7 Nelson and Sommers (1982) 
 Total nitrogen (N) Kjeldahl method Bremner and Mulvaney (1982) 

 Available phosphorus (P) Olsen’s method Olsen et al. (1954) 

 Potassium (K) Flame Photometer at 766.5 nm Toth and Prince (1949) 

 Calcium (Ca) and magnesium (Mg) Ethylenediamine Tetraacetic Acid (EDTA) Titration and use of AAS Cheng and Bray (1951) 

 Sodium (Na) Flame Photometry at 589 nm Robbins and Wiegand (1990) and Helmke and Sparks (1996) 
 
 

 

RESULTS AND DISCUSSION 

 

Effect of Shea waste slurry on soil pH and EC 

 

The use of cover crops, the application of high-
quality compost, the return of crop residue and the 
application of other natural fertiliser have been 
reported to work together to neutralise soil pH 
(ASFG, 2010). Low soil pH stress is a major 
growth-limiting factor for crop production in many 

 
 

 

regions of the world and the optimum pH for crop 
growth can vary among crop cultivars and soils 
(Fageria et al., 2011). According to Liu and 
Hanlon (2015), soil pH is one of the most 
important soil chemical properties which 
influences the solubility and bioavailability of 
essential plant nutrients.  

Slightly acidic soils with pH levels ranging from 
5.18±0.13 to 5.42±0.33 for both depths at KAD 
and 5.49±0.08 to 5.97±0.3 at KAN was recorded 

 
 

 

indicating how SWS influences soil pH (Table 3). 
For the Jisonayili soils, average pH of 5.67±0.10 
to 8.85±2.47 at JID were noted to be higher than 
that of JIN with pH of 7.62±0.49 to 7.56±0.62 
(Table 3).  

Though the effect of SWS application to soils in 
the two study locations did not statistically 
influence the level of pH by the ANOVA (Table 3), 
the mean for the upper depth (0-30 cm) of KAN 
was significantly higher than that of KAD. 



4 

 

  
 
 

 
Table 3. Mean pH levels in the study area soils. 

 

Site 
pH  ANOVA (α = 0.05) EC (µS/cm) ANOVA (α = 0.05) 

 

0-30 cm 30-60 cm F-stat F-pr 0-30 cm 30-60 cm F-stat Fpr 
 

 
 

KAD 5.18 ±0.13
b
 5.42 ±0.33

ab
 

3.59 0.124 
155.5±83.4

a
 75.8 ±40.7

a
 

2.44 0.204  

KAN 5.97 ±0.3
a
 5.49 ±0.08

ab
 41.15 ±3.89

a
 39.6 ±32.0

a
 

 

    
 

JID 8.85± 2.47
a
 5.67± 0.10

a
 

2.04 0.251 
52.8± 53.0

a
 47.4± 40.3

a
 

0.76 0.574  

JIN 7.62±0.49
a
 7.56±0.62

a
 110.2 ± 79.8

a
 40.65± 7.28

a
  

    
   

KAD = Kasalgu Applied Site; KAN = Kasalgu Non-Applied Site; JID = Jisonayilli Applied Site, JIN = Jisonayilli Non-Applied Site. F-stat = F-statistics; 

F-Pr = f-probability. Means that do not share a letter (
a
 or 

b
) are significantly different. Values after ± indicate Standard deviation. 

 
 

 

Liu and Hanlon (2015) noted that pH range from 5.5 to 
7.0 favours the solubility of essential nutrients thus 
indicating that the pH recorded for the two locations are 
suitable for the cultivation of crops. However, SWS 
application to soils in the Jisonayili resulted in increasing 
the pH from acidic to alkaline soils. A study by Adeli et al. 
(2008) reported that long-term treatments with anaerobic 
swine lagoon liquid reduced the soil pH by 0.97, 0.11, 
and 0.88. Sharpley et al. (2004) investigated soils with 
varying organic manure application histories and found 
that pH was significantly greater in manured soils than in 
untreated soils using poultry litter and swine slurry 
manure. Similar results were also reported by Oguike and 
Mbagwu (2001) for soil pH using organic manure for soil 
fertility amendments. Whalen et al. (2000) also observed 

a significantly higher pH for manure‐amended than 
unamended soil. Another study by Carmo et al. (2015) 
highlighted the potentials of organic wastes on increase 
soil pH and to elevated levels that may not be favourable 
for plant development. According to Fageria et al. (2010), 
the most useful soil pH for acid soils, is the minimum pH 
above which liming will not increase crop yield.  

Higher levels of EC of 155.5±83 and 41.15±3.89 µS/cm 
for the upper depth (0-30 cm) of KAD and KAN, 
respectively, reduced to 75.8±40.7 to 39.6±32.0 µS/cm at 
their respective lower depths (30-60 cm). Similarly, EC at 
the upper depths (0-30 cm) of JID and JIN, respectively 
decreased from 52.8±53.0 and 110.2±79.8 µS/cm to 
47.4±40.3 and 40.65±7.28 µS/cm at their lower depths 
(30-60 cm). However, the observed variations for both 
sites were statistically insignificant.  

The application of SWS as an organic soil amendment 
material thus increased the soil EC at Kasalgu. A study 
by Carmo et al. (2015), realised a slight increase in soil 
EC for medium-textured Oxisol by the addition of organic 
wastes. The increase of EC levels by application of 
organic waste on soil have earlier been reported by 
different authors (Tsadilas et al., 1995; Topper and 
Sabey, 1986; Hinesly et al., 1982). 

 

Plant primary nutrients in soils 
 
Increasing the soil  OM  as  well  as  pH increases  soil  P 

 
 
 

 

availability. The optimum pH for P availability is 6.0 to 6.5. 
If pH is outside this range, supplementary P may be 
needed even if soil tests show adequate P. K regulates 
osmotic balance, opening and closing of stomata and cell 
turgor pressure, while stimulating rooting, photosynthesis, 
chlorophyll formation, starch formation and translocation 
of sugars. Adequate K levels reduce plant susceptibility to 
insect and disease attack.  

As an essential component of chlorophyll, proteins, 
enzymes and hormones, N is essential for plant growth. 
N does not exist as a mineral element in the soil. It must 
be taken from the atmosphere, which is composed of 
approximately 78% N. However, plants cannot use 
atmospheric N until it is fixed into an available form such 
as ammonium or nitrate by free bacteria, algae in the soil 
and through symbiotic bacteria in nodules contained in 
the roots of legumes such as alfalfa and beans. Artificial 
sources of N (chemical fertiliser) are fixed through the 
Haber-Bosch process of reacting hydrogen and 
atmospheric N under heat and pressure to form 
ammonium (ASFG, 2010).  

Table 4 presents changes in soil %N content due to the 
influence of SWS. It can be observed from Table 4 that N 
levels increased from a low of 0.03±0.0% at KAN (0-30 
cm) to 0.56±0.2% at KAD while at the 30-60 cm, 
0.015±0.02 and 0.01±0.0% were recorded for the KAD 
and KAN soils, respectively. The results of the ANOVA at 
Kasalgu site were statistically significant with F-pr of 
0.012. The significant difference was observed for the 
mean concentration at KAD (0-30 cm) over the other soil 
samples (Table 4).  

N content increased from 0.04±0.01 at JIN (0-30 cm) to 
0.14±0.13% at JID while the 30-60 cm depth did not 
record any increment between the applied and the non-
applied soils. The variation among mean concentrations 
was statistically insignificant with f-probability values 
0.274, respectively (Table 4).  

At a depth of 0-30 cm, soil at KAN and JIN recorded 
lower than the 0.15% N-value recommended by Brady 
and Weil (1999) for cultivated soils resulting from the non-
application of SWS. Comparison between both depths 
indicates that the level of concentration of %N was higher 
at the applied soils, thus presenting the 



5 

 

 
 
 

 
Table 4. Mean primary plant nutrients in experimental soils.  
 

Site 
%N   ANOVA (α = 0.05) P (mg/kg)  ANOVA (α = 0.05) K (mg/kg) ANOVA (α = 0.05) 

 

0 - 30 cm 30 - 60 cm F-stat Fpr 0 - 30 cm 30 - 60 cm F-stat Fpr 0 - 30 cm 30 - 60 cm F-stat Fpr 
 

 
 

KAD 0.56 ± 0.2a 0.015 ± 0.02b 
14.97 0.012 

98.6 ± 21.9a 11.56 ± 12.29b 
27.16 0.004 

152.2 ± 14.3a 91.9 ±52.3ab 
10.84 0.022  

KAN 0.03 ± 0.0b 0.01 ± 0.01b 3.47 ± 0.62b 3.83 ± 1.35b 21.9 ± 2.39b 18.60±7.17b 
 

      
 

JID 0.14 ± 0.13a 0.01 ± 0.0a 
1.88 0.274 

262.0 ± 176a 8.10 ± 2.09b 
3.83 0.114 

231.6 ± 98.0a 52.4 ±21.5b 
7.43 0.041  

JIN 0.04 ± 0.01a 0.01 ± 0.0a 42.78 ± 1.52ab 11.00 ± 1.02b 43.96 ± 4.4b 21.98±7.17b 
 

      
 

 
KAD = Kasalgu Applied Site; KAN = Kasalgu Non-Applied Site; JID = Jisonayilli Applied Site, JIN = Jisonayilli Non-Applied Site. F-stat = F-statistics; F-Pr = f-probability. Means that do not share a letter 

(
a
 or 

b
) are significantly different. Values after ± indicate Standard deviation. 

 
 

 

contribution of applied SWS to increased 
concentration of %N. An experiment by Kaniz and 
Khan (2013) to reclaim saline soil using gypsum, 
rice hull, and rice straw resulted to an increase N 
content in plant straw which increase by the 
application of rice hull and sawdust as these 
treatments added organic matter, in turn, N to the 
soil. Murmu et al. (2013) also found that organic 
manure increases crop productivity, N utilisation 
efficiency, and soil health compared to chemical 
fertiliser. A study by Elbl et al. (2013) realised a 
significant decrease of N leaching by the 
simultaneous applications of soluble humic 
substances and compost to soils. According to Li 
et al. (2014), the growth and development of plant 
may largely depend on the N supplying capacity of 
the soil.  

A higher P concentration of 98.6±21.9 mg/kg at 
0-30 cm depth was recorded in soils of KAD as 
compared to a low level of 3.47±0.62 mg/kg at 
KAN. ANOVA at 5% resulted in a statistically 
significant difference between the soils which 
received SWS (specifically for KAD at 0-30 cm) 
and soils which did not, with F-pr of 0.004 (Table 
4). According to Hossain et al. (2018), the 
application of organic amendments at variable 
rates individually or in combinations showed a 

 
 
 

 

significant (p<0.05) positive influence on the P 
contents of rice plants grown under both Field 
Moist Condition and Standing Water Conditions.  

A higher P concentration of 262.0±176 mg/kg 
was recorded at JID (0-30 cm) while a relatively 
lower concentration of 42.78±1.52 mg/kg was 
noted for soils at JIN (0-30 cm) resulting from the 
non-application of SWS. However, P levels at JID 
(30 - 60 cm) was slightly lower (8.10±2.09 mg/kg) 
than that of JIN (11.00±1.02 mg/kg). The variation 
was not statically significant by ANOVA with F-pr 
of 0.114 (Table 4). Available P contents in the soil 
in Tamale area ranges from deficient to marginal 
(5.0-7.0 mg/kg) in the top soil (Agyare, 2004). The 
effect of SWS in increasing the levels of P in 
tropical soils was evident from the results of the 
study and based on the recommended value of 20 
ppm for crop cultivation (ASFG, 2010), the 
addition of SWS as an organic soil amendment 
material to increase P concentration in tropical 
soils has been realised. The higher level of P in 
SWS applied soils could also be attributed to the 
findings of Hinsinger (2001) which indicates that 
the distribution of P species (organic and 
inorganic) in soil is determined primarily by the pH 
of the soil solution. The study revealed that the pH 
of the soils at the SWS applied site increased, 

 
 
 

 

leading to P availability. Mokolobate and Haynes 
(2002) and Pypers et al. (2005) also reported that 
incorporation of organic residues can improve soil 
conditions making an increase in P availability 
possible.  

From Table 4, soils from the sampling points of 
Kasalgu recorded 152.2±14.3 and 21.9±2.39 
mg/kg of K at 0-30 cm depth for KAD and KAN, 
respectively. Concentration at the lower depth 
(30-60 cm) reduced to91.9±52.3 and 18.60±7.17 
mg/kg for KAD and KAN, respectively. ANOVA at 
5% resulted in f-probability of 0.022, indicating a 
significant difference. K concentration at the upper 
depth (0-30 cm) of KAD was significantly higher 
than the soils at KAN (Table 4).  

Soils sampled from the Jisonayilli community at 
0-30 cm recorded an average of 231.6±98 and 
43.96±4.4 mg/kg of K for JID and JIN soils, 
respectively with a decrease to 52.4±21.5 and 
21.98±7.17 mg/kg at their respective lower depths 
(30-60 cm). Comparatively, results of the ANOVA 
revealed that the mean concentration of K at the 
upper depth (0-30 cm) was significantly higher 
than the other samples at F-pr of 0.041 (Table 4). 
According to Hossner and Juo (1999), most 
tropical soils are highly weathered, infertile, acidic 
and have deficient levels of K. However, the 



6 

 

  
 
 

 
Table 5. Mean levels of secondary plant nutrients in soil.  
 

Site 
Na (meq/100 g) ANOVA (α = 0.05) Mg (meq/100 g) ANOVA (α = 0.05) Ca (meq/100 g) ANOVA (α = 0.05) 

 

0 - 30 cm 30 - 60 cm F-stat Fpr 0 - 30 cm 30 - 60 cm F-stat Fpr 0 - 30 cm 30 - 60 cm F-stat Fpr 
 

 
 

KAD 1.76 ± 0.39
a
 1.07 ± 0.46

ab
 

8.80 0.031 
8.51 ± 4.86

a
 1.47 ± 0.57

b
 

4.34 0.095 
6.3 ± 0.98

a
 1.87 ± 0.38

b
 

36.82 0.002  

KAN 0.46 ± 0.09
b
 0.37 ± 0.03

b
 1.19 ± 0.96

b
 0.80 ± 0.38

b
 1.6 ± 0.07

b
 1.74 ± 0.19

b
 

 

      
 

JID 2.81 ± 1.0
a
 0.57 ± 0.18

b
 

9.19 0.029 
3.21 ± 1.14

a
 0.80 ± 0.38

b
 

5.74 0.062 
6.14 ± 4.16

a
 2.41 ± 0.38

a
 

1.58 0.327  

JIN 0.72 ± 0.09
b
 0.53 ± 0.12

b
 0.80 ± 0.3

b
 0.81 ± 0.76

b
 4.68 ± 0.19

a
 2.27 ± 0.57

a
  

      
 

 
KAD = Kasalgu Applied Site; KAN = Kasalgu Non-Applied Site; JID = Jisonayilli Applied Site, JIN = Jisonayilli Non-Applied Site. F-stat = F-statistics; F-Pr = f-probability. Means that do not share a letter 

(
a
 or 

b
) are significantly different. Values after ± indicate Standard deviation. 

 
 

 

addition of SWS to soils in the tropical lands have 
been noted to influence significantly, the amounts 
of K but this was noted for this study to have 
decreased with increasing soil depth. ASFG 
(2010) reported that, at a depth of 0-30 cm, K is 
high in applied soils but low in non-applied soils 
while at 30-60 cm it was generally low in all the 
soils. 
 
 

 

Secondary plant nutrients in soils 

 

A number of secondary nutrients such as iron, 
manganese, zinc, copper, boron, chlorine and 
molybdenum are known to influence plant growth 
and are usually required in small amounts for 
proper functioning of plant metabolism. The 
absolute or relative absence of any of these 
nutrients can hamper plant growth; alternatively, 
too high a concentration can be toxic to the plant 
or to humans (Gruhn et al., 2000).  

As an organic soil amendment material, the 
study evaluated the effect of the application of 
SWS on availability of Mg, Ca and Na and results 
presented in Table 5.  

Na levels in soils of KAD recorded higher  levels 

 
 
 

 

of 1.07±0.46 to 1.76±0.39 meq/100 g while KAN 
soils recorded levels ranges from 0.37±0.03 to 
0.46±0.09 meq/100 g. A statistically significant 
difference of Na concentration (Table 5 and Figure 
1) was realised with F- pr of 0.031. Na 
concentration of the upper depth (0-30) of KAD 
was significantly different from soils at KAN (Table 
5).  

Na concentration in soils of JID ranged from 
0.57±0.18 to 2.81±1.0 meq/100 g while JIN soils 
recorded 0.53±0.12 to 0.71±0.09 meq/100 g 
concentration levels. ANOVA at 5% resulted in 
statistical difference with F-pr of 0.029. The 
maximum mean concentration of Na at the upper 
depth (0-30 cm) of JID was significantly different 
over all the samples of the study site (Table 5).  

Mg levels of 8.51±4.86 and 1.19±0.96 meq/100 
g reduced with depth to 1.47±0.57 and 0.80±0.38 
meq/100 g for KAD and KAN, respectively (Figure 
2). ANOVA at 5% significant level indicates that 
the difference in Mg concentration is insignificant 
with F-pr of 0.095. However, the maximum Mg 
concentration of KAD at 0-30 cm was significantly 
higher than all the soil samples (Table 5).  

Soil Mg concentration at JID reduced from 

3.21±1.14 to 0.80±0.38 meq/100 g for 0-30 and 

30-60 cm, respectively. At JIN,  Mg  concentration 

 
 
 

 

was virtually the same for both depths (Figure 2). 
Once more, the highest Mg concentration 
recorded for SWS at 0-30 cm was significantly 
different from all the soil samples though the 
results of ANOVA was statistically significant with 
F-Pr of 0.062 (Table 5). The concentration of Mg 
in soils applied with SWS was noted to be 
influenced by high levels of soil pH. According to 
Maathuis et al. (2011), concentration of Mg is 
dependent on soil OM content, pH and the 
presence of other cations. The availability of Mg 
for plants is thus ultimately reduces by soil acidity 
(Maathuis et al., 2011).  

The maximum soil Ca of 6.30±0.98 meq/100 g 
recorded at the upper depth (0-30 cm) of KAD 
showed a highly significant difference with all the 
other samples at the study site by ANOVA with F-
pr of 0.002. Despite the reduction in Ca 
concentration at Jisonayilli site, for the various 
depths, there was no significant difference among 
mean concentrations with F-pr of 0.327 by 
ANOVA (Table 5 and Figure 3). An experiment by 
Mubarak et al. (2009), found a significant increase 
(P 0.02) in Ca and Mg with the application of wool 
and hoof powder for amendment of sandy soils. 
However, residues of pigeon pea (dried or fresh) 
and baggase had no significant effects on soil pH 



7 

 

 
 
 

 

(m
eq

/1
00

g

) 

5.0                         
 

4.0                  2
.8

1
 

    
 

                          

M
ea

nL
ev

el
o

fN
a 

3.0 

                        
 

                        
 

2.0 
 1

.7
6
 

 1
.0

7
 

 0
.4

6
 

 0
.3

7
 

     5
7

0
. 

 

                          

                         
 

 

1.0 

                        
 

                         
 

                         
 

 

0.0 

                        
 

                         
 

                         
 

 
 
                       

 

   

KAD 

   

KAN 

   

JID 
 

           
   

Study Site 
 

Figure 1. Mean Na level at the study areas. 
 
 
 

 

(m
e

q
/1

0
0

g
) 15.0                        

 

8
.5

1
 

                    
 

10.0                        
 

                        
 

o
f 

M
g

      

1
.4

7
 

 

1
.1

9
 

 

8
0
0
. 

 

2
1
3
. 

8
0
0
. 

 

        
 

M ea n
L

ev el
 

5.0 
       

 

                        
 

 

0.0 

                       
 

                        
 

                        
 

                        
 

                        
 

                        
 

                        
 

   

KAD 

  

KAN 

   

JID 

 

         
   

Study Site 

 
 
 
 
 
 

 

0-30 cm 
 

30-60 cm 
 
 
 
 
 
 
 

0
.7

2
 

 0
.5

3
 

        

        
 

JIN 
 
 
 
 
 
 
 
 
 

 

0-30 cm 
 

30-60 cm 
 
 
 
 
 
 
 

 

8
0
0
. 

8
1
0
. 

 

   
 

    
 

    
 

 

JIN 

 
 

Figure 2. Mean Mg level at the study areas. 
 
 

 

and the soluble cations (Ca, Mg and Na). 
 

 

Shea waste slurry effect on soil OM and OC content 

 

Use of cover crops, return of crop residue, addition of 
compost and/or composted manure and practices that 
maintain OM on the surface of the soil all increase OM 
levels (ASFG, 2010). 

 
 
 
 

 

High levels of soil %OM (0.35±0.09 to 10.9±3.95%) 
were recorded at KAD while the KAN fields recorded 
0.29±0.02 and 0.58±0.01% (Table 6). The variation 
among mean concentrations was statistically significant 
(F -pr 0.013) with %MO of KAD at 0 - 30 cm being 
significantly higher than the other samples at the site. 
Also, at JID, 0.29±0.03 to 2.45±2.15% of %OM was 
recorded while 0.23±0.08 to 0.88±0.10% was measured 
for JIN. The results of ANOVA indicated no significant 



8 

 

  
 
 

 
Table 6. Mean percentage OM content in the soil.  
 

Site 
%OM  ANOVA (α = 0.05) %OC  ANOVA (α = 0.05) 

 

0 - 30 cm 30 - 60 cm F-stat Fpr 0 - 30 cm 30 - 60 cm F-stat Fpr 
 

 
 

KAD 10.94±3.95
a
 0.35±0.09

b
 

14.25 0.013 
6.36±2.29

a
 0.21±0.05

b
 

14.28 0.013  

KAN 0.58±0.01
b
 0.29±0.02

b
 0.34± 0.11

b
 0.17±0.0

b
 

 

    
 

JID 2.45 ±2.15
a
 0.29±0.03

a
 

1.85 0.279 
1.43 ± 1.25

a
 0.17±0.03

a
 

1.84 0.280  

JIN 0.88 ± 0.10
a
 0.23±0.08

a
 0.51±0.10

a
 0.14±0.05

a
  

    
 

 
KAD = Kasalgu Applied Site; KAN = Kasalgu Non-Applied Site; JID = Jisonayilli Applied Site, JIN = Jisonayilli Non-Applied Site. F-stat = F-statistics; F-

Pr = f-probability. Means that do not share a letter (
a
 or 

b
) are significantly different. Values after ± indicate Standard deviation. 

 
 

 

M
e
a
n

 L
e
v
e
l 

o
f 

C
a
 (

m
e
q

/1
0
0
g

) 

 
 

 

15.0  
 
 

 

10.0                  6.
14

 

             
 

                                  

3
0

6
. 

                              
 

                              
 

5.0 

    

8
7

1
. 

 

5
5

1
. 

 

1
.7

4
 

     

2
.4

1
 

 

6
8

4
. 

 

2
7

2
. 

 

            

 

 

            
 

            
 

                 
 

0.0 

                 
 

     

 

           
 

                      
 

                                 
 

  

KAD 

 

KAN 

   

JID 

    

JIN 
 

           
  

Study Site 

 
 
 
 

 

0-30 cm 
 

30-60 cm 

 

Figure 3. Mean Ca level at the study areas. 
 

 

differences (F-pr 0.279) among the mean %OM at the 
study site (Table 6). Comparison between both depths 
clearly indicates that the level of %OM accumulation in 
the soils decreases with increasing depth in both soils. It 
is observed from the findings of the study that the OM 
content is a clear improvement over the findings of 
Fening et al. (2005) with the indication that soils in the 
interior savanna zone have low organic matter contents 
(1.0 ±0.4%) and low levels of the major plant nutrients. 
Seçer et al. (2016), similarly recorded a significant 
increase in soil OM with the application of organic waste 
products of oily oregano and cumin.  

Soil organic amendments such as manures and plant 
residues are a significant source of OC to the soil. Plants 
also promote microbial populations and subsequent 
turnover by exuding OC from their roots (Merckx et al., 
1985). The application of SWS was observed to also 
influence the percentage levels of OC content of the 
study soils. High levels of %OC (Table 6) were recorded 
in the two sites to which SWS were applied. However, the 
difference in mean concentration of %OC was statistically 

 
 
 

 

significant at Kpsalgu site only with a significantly higher 
concentration at the upper depth (0-30 cm) of KAD (Table 
6). In a similar study, Chen et al. (2019) observed an 
increase in soil OC when different organic waste was 
applied. Landon (1991) reported an average of 0.5% of 
OC content as a requirement for tropical crops, whilst 
Young (1976) also reported that tropical crops require an 
average range of 0.6 to 1.2% of carbon content for proper 
growth and development. The increased percentage OC 
content of soils was noted to have been influenced by the 
application of SWS thus indicating it as a good source of 
organic manure for soil fertility amendments especially in 
degraded tropical soils. Mekki et al. (2017), after 
observing a significant increase in soil OM and OC from 
application of biowaste compost noted That soil OC 
content is critical for the maintenance of soil quality and 
balance of the terrestrial carbon cycling. 

 

Conclusions 
 
The  results of the study indicated that the application of 



9 

 

 
 
 

 

SWS as an organic soil amendment material resulted in 
increased concentration levels of plant primary nutrients 
(N, P and K) and also secondary nutrients such as Na, 
Ca and Mg. The application of SWS also influenced soil 
pH, percentage OM and carbon content percentage and 
soil EC by increasing their levels. The application of SWS 
as an organic soil amendment material thus affected soil 
chemical properties positively and thus will translate to 
the availability of the necessary plant nutrients for plant 
growth and yield. Comparison between both depths 
indicates that the level of %OM accumulation in the soils 
decreases with increasing depth in both soils. The 
application of SWS also influenced the percentage levels 
of OC content of the study soils. The study noted and 
concluded that SWS has a nutrient influencing effect and 
therefore could be used as an organic soil amendment 
material for plant growth as well as soil physical 
properties improvement. 
 

 

CONFLICT OF INTERESTS 

 

The authors have not declared any conflict of interests. 
 

 
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