Quantification of soil and nutrient loss due to yam harvesting: A case study in two local government areas in Benue state, Nigeria

Abstract

Soil loss due to crop harvesting is a recognized erosion process which has significantly contributed to soil degradation. Despite its significance, soil loss due to crop harvesting has been given little attention in Benue state and Nigeria at large. This is evident in the paucity of information on soil loss due to crop harvesting in Nigeria. Therefore a field experiment was conducted to quantify soil and nutrient loss due to yam harvesting in two local government areas (Kwande and Ushongo) of Benue state and to identify factors which could contribute to soil loss in these areas. Data collected on soil loss were subjected to t-test at α = 0.05. Average crop yield in Kwande was 18.9 t ha-1 and 16.3 t ha-1 in Ushongo with corresponding soil loss of 3.26 t ha-1 harvest-1 and 1.97 t ha-1 harvest-1 respectively. Higher soil loss observed in Kwande compared to Ushongo can be attributed to higher crop yield and clay content of the soil. Crop yield, clay content and soil organic matter correlated positively with soil loss in Kwande (r = 0.75, r = 0.58, r = 0.65) while in addition to crop yield and clay content sand correlated negatively with soil loss in Ushongo (r = 0.77, r = 0.60, r =-0.60). Soil nutrient losses for nitrogen , phosphorus and potassium were significantly higher in Kwande compared to Ushongo by 2.71, 2.67 and 2.02 times respectively. The findings suggest that soil loss in these areas could degrade the land within a short time, especially where mono-cropping of yam is practiced. Farmers are therefore advised to hand-rub yam tubers while harvesting on the field and practice crop rotation.

Full text

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Quantification of soil and nutrient loss due to yam harvesting: A case study in two local government
areas in Benue state, Nigeria.
ARTICLE INFO
Article history:
Received June 28, 2021
Received in revised form July 21, 2021
Accepted August 29, 2021
Available online September 27, 2021
ABSTRACT
Soil loss due to crop harvesting is a recognized erosion process which has signifi-
cantly contributed to soil degradation. Despite its significance, soil loss due to
crop harvesting has been given little attention in Benue state and Nigeria at large.
This is evident in the paucity of information on soil loss due to crop harvesting in
Nigeria. Therefore a field experiment was conducted to quantify soil and nutrient
loss due to yam harvesting in two local government areas (Kwande and Ushongo)
of Benue state and to identify factors which could contribute to soil loss in these
areas. Data collected on soil loss were subjected to t-test at α = 0.05. Average
crop yield in Kwande was 18.9 t ha-1 and 16.3 t ha-1in Ushongo with correspond-
ing soil loss of 3.26 t ha-1 harvest-1 and 1.97 t ha-1harvest-1 respectively. Higher
soil loss observed in Kwande compared to Ushongo can be attributed to higher
crop yield and clay content of the soil. Crop yield, clay content and soil organic
matter correlated positively with soil loss in Kwande (r = 0.75, r = 0.58, r = 0.65)
while in addition to crop yield and clay content sand correlated negatively with
soil loss in Ushongo (r = 0.77, r = 0.60, r = -0.60). Soil nutrient losses for nitro-
gen, phosphorus and potassium were significantly higher in Kwande compared to
Ushongo by 2.71, 2.67 and 2.02 times respectively. The findings suggest that soil
loss in these areas could degrade the land within a short time, especially where
mono-cropping of yam is practiced. Farmers are therefore advised to hand-rub
yam tubers while harvesting on the field and practice crop rotation.
Keywords:
soil loss
crop yield
nutrient loss
degrade
Corresponding Author’s E-mail Address:
Samson.victor@uam.edu.ng +23480606889069
https://doi.org/10.36265/njss.2021.310306
ISSN– Online 2736-1411
Print 2736-142X
© Publishing Realtime. All rights reserved.
Department of Soil Science, College of Agronomy, Federal University of Agriculture, Makurdi, Nigeria.
1.0 Introduction
Soil loss due to crop harvesting (SLCH) has been widely
recognized as a contributor to land degradation. In Sub-
Saharan Africa with Nigeria inclusive, effort have been
made to reduce soil erosion, particularly water and wind
erosion. However, considerable soil masses are exported
from cropped land during harvesting of root, tuber, bulb
and some legume crops such as yam, cassava, onion and
groundnut (Dada et al., 2016;Isabirye et al., 2007; Mwan-
go et al., 2015). Soil and associated nutrients sticking to
harvested crop that is removed from the field is referred to
as soil loss due to crop harvesting (Poesen et al., 2018;
Ruysschaert et al., 2004.). SLCH cause loss of valuable
top soil and nutrients (Oshunsanya et al., 2018a; Oshun-
sanya et al., 2018b;Sumithra et al., 2013.). Mean SLCH
has shown to be similar to that of water erosion in many
countries of the world.(Oshunsanya et al., 2018b;Poesen et
al., 2001).
SLCH is of great significance especially on gentle slopes
and flat lands where there is lesser risk of water and wind
erosion. For example Isabirye et al. (2007) reported SLCH
of 3.4 t ha-1 due to harvesting of cassava. Similar-
ly,Oshunsanya and Samson (2019) in a study reported
SLCH of 1.3 t ha-1 for cassava in Nigeria. In another study
Parlak et al. (2018) reported 4.00 Mg ha-1 average SLCH
for celery. The severity of SLCH varies depending on sev-
eral factors such as crop type, soil properties and harvest-
ing technique amongst others. For instance, Faraji et al.
(2017) suggested soil moisture content to be a contributor
to SLCH, Similarly Oshunsanya et al. (2018b) suggested
root hair density as a factor that could influence SLCH. In
like manner crop age was attributed to be a factor respon-
sible for SLCH (Isabirye et al., 2007).
Although SLCH has been documented for several crops in
some countries of the world, however, it is still under re-
ported in Nigeria. Furthermore there is paucity of infor-
mation on SLCH across different Agro-ecological zones.
In addition, despite being the largest producers of yam
globally most farmers in Benue state are either unaware or
underrate this process of erosion. Generally during har-
vesting of yams, the tubers are rarely cleaned on the field
as a result, some quantity of soil is exported from the farm
to the farmers house, storage facility and market place.
Therefore this study was conducted to i. quantify soil loss
due to yam harvesting. ii. estimate nutrient loss due to yam
harvesting. iii. identify factors that contribute to SLCH in
the study area.
Victor Manna Samson* and Kumawuese Mercy Ityavnongo
Samson and Ityavnongo NJSS 31 (3) 2021 42-47

43
2.0. Materials and methods
2.1 Study area
The study was conducted 2019 at Kwande and Ushongo
local government areas in Benue State, Nigeria. The study
location in Kwande lies between latitude 06˚ 88′ 50.10″ N
and longitude 09˚ 24′ 41.30″ E.While Ushongo location
lies between 06˚ 94′ 21.67″ N and longitude 09˚ 31′ 05.20″
E. Both locations have a mean annual rainfall of about
1400 mm. The rain generally starts from April and spans
through the late October. The temperatures of the locations
are generally high throughout the year with February and
March as the hottest months.The soils of Kwande consist
of masses of basement complex rocks and plateau of ba-
saltic rocks. Soil texture in the study location was sandy
clay loam at Kwande and sandy loam at Ushongo. The
predominant crop grown in both locations are yam, millet
and maize.
2.2 Sampling methodology
Crop and soil samples were taken when farmers were har-
vesting the crops. The harvested area was divided into 15
replicates in each location. Each sub-plot measured 5 m ×
4 m (20 m2). Yam was grown as a sole crop on mounds
spaced at 1 m × 1 m. The average plant density was
10,000 plants per hectare. Harvesting was done at 8
months after planting. The harvested yam tubers were
carefully dug out of the mounds using hoes. The tubers
were weighed with soil attached and thereafter the tubers
were rubbed and cleaned to remove the adhering soil (Fig
1). The soil was air-dried and weighed using a weighing
scale. The soil samples collected were then packed into
polythene bags and taken to the laboratory for nutrient
analysis. Soil samples were also collected from each sub-
plot to determine the soil physical and chemical properties
at harvesting.
2.3 Soil analysis
Soil samples were collected from each subplot at 0–30 cm
depth at harvesting. Disturbed soil samples were collected
with a soil auger, while 5 cm × 5 cm cylindrical cores
were used to take undisturbed soil samples for assessment
of baseline and post-harvest status of the soil and treat-
ment effects on soil properties. The soil pH was measured
in a 1:1 ratio mixture of soil and distilled water (Mclean,
1982). The soil organic carbon content was determined
using the Walkley-Black wet-oxidation method (Walkley
and Black,1934) as described by Nelson and Sommers
(1982), while the total nitrogen content was determined
using the macro-kjeldahl digestion-distillation apparatus
following Bremmer and Mulvaney (1982) procedure. Mel-
ich III was used to extract the soil available phosphorus
and the absorbance was read using the spectrophotometer
(Olsen and Sommers, 1982).The soil exchangeable acidity
was determined using the KCl extraction method, while
the exchangeable bases were determined using neutral
ammonium acetate as the extractant (Rhodes, 1982). Cal-
cium and magnesium were determined from the extract by
0.01 M EDTA titration method, while sodium and potassi-
um were determined using the flame photometer (Jackson,
1970). The soil Fe, Cu, Mn, and Zn contents were deter-
mined using the hydrochloric acid procedure as described
by Rhodes (1982). The particle size distribution of the soil
was determined using Bouyoucos hydrometer method as
described by Gee and Or (2002). After oven-drying the
soil samples to constant weight at 105°C, the soil bulk
density was computed as described by Grossman and
Reinsch (2002). Gravimetric moisture content was also
computed as described by Grossman and Reinsch (2002).
2.4 Soil loss determination
The soil loss value per unit of crop mass (SLCHspec), the
total soil loss for a given crop per unit area (SLCHcrop)
and nutrient losses were determined as outlined by Ruyss-
chaertet al. (2004; 2007).
2.4.1 Soil loss per unit of crop mass (SLCHspec)
The soil loss value per unit of crop mass (SLCHspec) was
calculated using
SLCHspec(kg kg-1) = (1)
Where Mds = mass of exported air-dried soil in kg, Mrf=
mass of rock fragments (kg) and Mcrop= net crop mass
(kg). In this study, Mrf was zero, because harvesting was
done manually, not involving removal of stones from the
field. The Mcrop was not equal to the net crop mass as
proposed by Ruysschaertet al. (2004) but equaled gross
crop mass (silt + crop) because the accuracy of the field
balance could not measure the difference between net and
gross crop mass.
2.4.2 Soil loss due to crop harvest (SLCHcrop)
SLCHcrop was calculated using
SLCHcrop(t ha-1 harvest-1) = SLCHspec × Mcy
(2)
Where Mcy, = crop yield (t ha-1 harvest-1)
2.4.3 Soil nutrient loss estimation
Nutrient loss through crop harvesting was expressed on
elemental basis and was estimated using the following
equation:
Nutrient loss (kg ha-1 harvest-1) = Nutrient content (g kg-1
soil) × 10 × SLCHcrop (t ha-1 harvest-1).
2.5 Data analysis
Data collected were subjected to a normality test (Leven’s
test) to verify the distribution pattern of the variables be-
fore subjecting to statistical analysis. Data were normally
distributed for both locations. Data on tuber yield, soil
loss, soil properties and soil nutrient loss were subjected to
t – test at α = 0.05 using GenStat 17th edition. Pearson’s
correlation coefficients and significance levels were deter-
mined between dependent variables (SLCHcrop and
SLCHspec) and independent variables (yam tuber yield,
moisture content, bulk density, sand, silt, clay, soil organic
matter)..
3.0. Results and Discusion
3.1 Soil loss due to yam harvest
SLCHspec due to yam harvest in Kwande and Ushongo
was not significantly (P > 0.05) different (Table 1). How-
ever SLCHspec was slightly higher in Kwande compared
to Ushongo by 41.7%. In contrast, SLCHcrop was signifi-
cantly (P < 0.05) higher in Kwande compared to Ushongo
by 65.5%. This difference could be attributed to the signif-
icant difference in tuber yield. Yam tuber yield was ob-
served to be considerably higher for Kwande than Ushon-
Quantification of soil and nutrient loss due to yam harvesting: A case study in two local government areas in Benue state, Nigeria.

44
go. Several researches have reported crop yield to directly
influence SLCH (Faraji et al., 2017;Oshunsanya et al.,
2018a; Parlak et al., 206; Ruysschaert et al., 2007.). For
instance Oshunsanya and Samson (2019) in an experiment
reported crop yield to be responsible for differences in
SLCH between four cassava varieties. Higher yield ob-
served in Kwande could be as a result of the higher inher-
ent soil nutrient status of the soil in Kwande (Table 2).
Oshunsanya et al. (2018b) reported increase in yam yield
as a result of increase in soil nutrients through fertilizer
application
Another factor that may be responsible for the higher
SLCH in Kwande could be the higher clay content ob-
served in Kwande (Table 1). Clay particles through its
properties could adhere more to rough tubers consequently
causing more soil to be attached to the harvested tubers.
Therefore as clay content increases SLCH is expected to
increase. This finding is in agreement with the result of
Dada et al (2016) who reported that much soil loss was
observed in area with higher clay content compared to area
with lower clay content during yam harvesting. In another
experiment, Parlak et al. (2016) reported a similar result of
clay content as a major contributor to SLCH during har-
vesting of carrot in Turkey.
Kwande Ushongo
Parameter Mean (min-max) Mean (min-max) P value
SLCHspec (kg kg-1) 0.17(0.09-0.33) 0.12(0.05-0.24) Ns
SLCHcrop (t ha-1 harvest-1) 3.26(1.50-5.90) 1.97(1.00-4.50) 0.003
Yam yield (t ha-1harvest-1) 18.90(14.5-21.2) 16.32(14.4-24.0) 0.002
Sand (g kg-1) 661.70(535.2-716.4) 696.40(669.2-715.2) Ns
Silt (g kg-1) 109.50(66.80-130.00) 119.00(90.00-140.00) Ns
Clay (g kg-1) 228.80(163.60-358.00) 184.60(152.00-230.80) 0.002
Bulk density (Mg m-3) 1.41 (1.40-1.44) 1.42(1.40-1.46) Ns
Gravimetric moisture content (%) 2.00(0.90-4.00) 2.32(0.70-5.00) Ns
Soil organic carbon (g kg-1) 23.09(19.60-31.10) 7.96(5.40-9.40) <0.001
Soil organic matter (g kg-1) 39.81(33.79-53.62) 13.72(9.31-16.21) <0.001
Table 1 Soil loss due to yam harvesting and related soil properties of yam plots in Kwande and Ushongo
min-max= minimum-maximum; ns= not significant
Kwande Ushongo
Parameter Mean (min-max) Mean (min-max) P value
Nitrogen (g kg-1) 1.01(0.84-1.20) 0.73(0.43-0.92) <0.001
Phosphorus (mg kg-1) 4.42(3.86-4.90) 3.34(2.96-3.80) <0.001
Potassium(cmol kg-1) 0.25(0.22-0.28) 0.24(0.21-0.28) Ns
Calcium (cmol kg-1) 2.95(2.78-3.10) 2.82(2.70-3.10) 0.012
Sodium (cmol kg-1) 0.22(0.19-0.25) 0.22(0.20-0.26) Ns
Magnesium (cmol kg-1) 2.81(2.68-2.92) 2.69(2.50-2.84) 0.019
Table 2 Soil nutrient status of the experimental fields
min-max= minimum-maximum; ns= not significant
3.2 Soil nutrient loss due to yam harvest.
Nitrogen, phosphorus and potassium losses were signifi-
cantly (P<0.05) different (Table 3). Mean soil nutrient loss
due to yam harvest showed that nitrogen, phosphorus and
potassium losses were higher for Kwande compared to
Ushongo by 2.71, 2.67, 2.02 times respectively. Higher
nutrient loss observed for Kwande compared to Ushongo
can be ascribed to differences in crop yield and inherent
soil nutrient content (Table 2) because soil nutrient loss is a
product of SLCH and nutrient content. The higher yield in
Kwande resulted to higher soil loss thus affecting soil nutri-
ent loss indirectly. Soil organic matter is another factor that
could be responsible for the differences in soil nutrient loss.
Soil organic matter plays an important role in improving
nutrient retention which could consequently lead to increase
in nutrient content of the soil. In this study, organic matter
content was observed to be significantly higher at Kwande
(Table 1). This could be the reason for the higher nutrient
content and consequently higher nutrient loss. A similar
observation was made by Isabirye et al. (2007) who re-
ported differences in soil nutrient losses for cassava and
sweet potato was partly as a result of crop yield. In another
experiment, Mwango et al. (2015) attributed differences in
crop yield and inherent fertility status of the top soil to be
responsible for differences in nutrient losses due to crop
harvest for different crops and in different villages. Aver-
age soil nutrient loss due to crop harvest in this study was
higher than losses reported for sweet potato (0.14 kg N ha-
1, 0.01 kg P ha-1 and 0.15 kg K ha-1) by Isabirye et al.
(2007) and sugar beet (3.35 kg N ha-1, 0.04 kg P ha-1 and
4.80 kg K ha-1) by Faraji et al. (2017). These differences
could be ascribed to differences in soil structure, texture
and top soil nutrient concentration.
Kwande Ushongo
Parameter Mean (min-max) Mean (min-max) P value
Nitrogen (kg ha-1) 36.69(19.00-70.80) 13.35(7.31-21.84) <0.001
Phosphorus (kg ha-1) 0.16(0.08-0.29) 0.06(0.04-0.09) <0.001
Potassium (kg ha-1) 8.99(4.37-15.34) 4.46(2.70-5.88) 0.003
Table 3 Soil Nutrient Losses due to Yam Harvesting
3.3 Relationship between SLCH, crop yield and soil proper-
ties
Table 4 and 5, shows relationship between soil loss
(SLCHspec and SLCHcrop) and crop yield and soil proper-
min-max= minimum-maximum; ns= not significant
ties. At Kwande, positive significant (P<0.05) relationship
was observed between SLCHspec and crop yield (r = 0.70),
clay (r = 0.54) and soil organic matter (r = 0.62) (Table 4). A
similar trend was observed in Ushongo, significant positive
Samson and Ityavnongo NJSS 31 (3) 2021 42-47

45
(P<0.05) relationship was observed between SLCHspec
and crop yield (r = 0.73) and clay (0.56). On the other
hand a negative significant (P<0.05) relationship was ob-
served between SLCHspec and sand ( r = 0.56) (Table 5).
This implies that as crop yield increases, soil loss could
increase as well. This is because crop yield increase could
be in terms of higher number of tubers and size moreover
this could translate to more tubers surface to which soil
can adhere.
Increase in clay content leads to decrease in sand content.
Therefore increase in clay content could imply increase in
finer and smaller soil particles with higher surface area
which could easily stick to tubers as against coarse and
larger soil particles. This can be further explained by the
negative correlation observed between sand and clay in
both locations (Table 4 and 5). The positive relationship
between SLCH with crop yield and clay could be partly
responsible for the difference in SLCH between the two
locations. Kwande was observed to have significantly
higher yield and clay content compared to Ushongo. Simi-
lar observation has been reported by some researches
(Dada et al., 2016; Mwango et al., 2015; Ruysschaert et
al., 2006.). For instance, Li et al. (2006) in an experiment
reported that SLCH was related to clay content for sugar
beet. Similarly, Parlak et al. (2016) in another experiment
reported crop yield and soil moisture content in addition to
clay to greatly influence soil loss during carrot harvesting.
In contrast soil moisture content in this study had no sig-
nificant relationship with soil loss. This could be as a re-
sult of the little variation in soil moisture. Moreover, yam
was harvested in the dry season when the soil moisture
content was low. This could have contributed to why no
significant relationship was observed between soil mois-
ture and SLCH.
SLCHcrop Crop yield Sand Clay Silt SOM BD GM
SLCHspec 0.98** 0.70** -0.36 0.54* -0.42 0.62* -0.11 0.16
SLCHcrop 0.75** -0.39 0.58* -0.40 0.65* -0.16 0.21
Crop yield -0.53* 0.67* 0.77** 0.60* -0.09 0.11
Sand -0.97** 0.25 0.31 0.18 -0.19
Clay -0.48 0.35 -0.32 0.25
Silt 0.28 0.16 0.32
SOM -0.36 0.18
BD -0.12
Table 4 Pearson correlation coefficient between SLCH parameters, crop yield and soil properties at Kwande
**= significant at 0.01; *= significant at 0.05; SOM = soil organic matter; BD = bulk density; GM = gravimetric moisture content
SLCHcrop Crop yield Sand Clay Silt SOM BD GM
SLCHspec 0.91** 0.73** -0.55* 0.56* -0.34 0.31 -0.12 0.23
SLCHcrop 0.77** -0.60* 0.60* -0.37 0.39 -0.21 0.27
Crop yield -0.47 0.13 -0.05 0.37 -0.41 0.35
Sand -0.89** 0.20 -0.54* 0.43 -0.17
Clay -0.83 0.43 -0.35 0.06
Silt 0.17 0.19 0.36
SOM -0.42 0.25
BD -0.12
Table 5 Pearson correlation coefficient between SLCH parameters, crop yield and soil properties at Ushongo
**= significant at 0.01; *= significant at 0.05; SOM = soil organic matter; BD = bulk density; GM = gravimetric moisture content
3.5 Implication of soil loss due to crop yam harvesting
Average soil loss due to yam harvesting in this study was
about 2.62 t ha-1 harvest-1. Losses of such magnitude must
not be neglected, as continuous removal of soil in this quan-
tity will lead to a rapid decline in soil productivity and land
degradation. Where crop yield and soil moisture condition is
higher, the soil loss could even be higher in quantity. Benue
state is the largest producers of yam in Nigeria. Assuming
about 3.5 million metric tons of yam is produced annually,
this implies about 5.25 × 104 tons of soil could be removed
during harvesting of yam. This could affect the sustainability
of the soil especially where mono-cropping of yam is prac-
Quantification of soil and nutrient loss due to yam harvesting: A case study in two local government areas in Benue state, Nigeria.
Figure 1: Pictorial view of weighing of yam and soil loss.

46
ticed.
Another implication of soil loss is the associated nutrients
removed during the process. Hence nutrient loss will reduce
the farmer’s financial benefit in terms of cost of replacing the
nutrients. In most cases, after harvesting of yams, farmers
transport their yams directly to houses, markets or storage
facilities without removing the adhering soil. These soils are
further washed into canals and drainage from the market and
houses, thus contributing to environmental pollution as nutri-
ents from the soil could be discharged into water bodies. Yu
et al. (2016) reported that about 3% and 20% of nitrogen and
phosphorus loads in water bodies comes from soil nutrient
loss. Continuous discharge of nutrients into water bodies
could contaminate water and also cause turbidity, which
could pose a great threat to aquatic organisms.
4.0 Conclusion
Soil loss due to yam harvesting was higher in Kwande com-
pared to that of Ushongo. This can be attributed to difference
in crop yield and clay content of both locations. As a result,
soil nutrient losses due to yam harvesting in Kwande were
also higher compared to Ushongo. Soil loss due to yam har-
vesting will not only lead to rapid degradation of the field but
will also reduce the farmer’s financial benefit. Therefore
farmers are advised to shake and hand-rub yam tubers while
harvesting. In addition it is suggested that farmers practice
crop rotation with cereals and legumes which may not have
the tendency of causing soil loss.
References
Bremmer, J. M., Mulvaney, C. S., 1982. Total nitrogen.In
Page, A. L et al. Eds. Methods of soil analysis Part 2,
Agronomy Monograph 9 (2nd edition).Soil Science Soci-
ety of America. pp. 403-430.
Dada, P.O.O., Adeyanju, O.R., Adeosun, O.J. andAdewumi,
J.K. 2016.Effects of soil physical properties on soil loss
due to manual yam harvesting under a sandy loam envi-
ronment.International Soil and Water Conservation Re-
search. 4: 121–125.
Faraji, M., Chakan, A.A., Jafarizadeh, M. and Behbahani,
A.M. 2017. Soil and nutrient losses due to root crops
harvesting: a case study from southwestern Iran, Ar-
chives of Agronomy and Soil Science. 63(11): 1523-1534
DOI: 10.1080/03650340.2017.1296133
Gee, G. W., Or, D., 2002. Particle size analysis. In Dane, J.
H. and Topp, G. C. Eds. Methods of soil analysis. Physi-
cal methods (Part 4).Soil Science Society of America.
pp. 255-295.
Grossman, R. B., Reinsch, T. G., 2002. Bulk density and
linear extensibility: Core method. In Dane, J. H. and
Topp, G. C. Eds. Methods of soil analysis. Physical
Methods (Part 4).Soil Science Society of America.pp.
208-228.
Isabirye, M., Ruysschaert, G., Van linden, L., Poesen, J.,
Magunda, M.K. andDeckers, J. 2007. Soil losses due to
cassava and sweet potato harvesting: a case study from
low input traditional agriculture. Soil Tillage Research
92: 96–103.
Li, Y., Ruysschaert, G., Poesen, J., Zhang, Q. W., Bai, L. Y.,
Li, L., Sun, L. F., 2006. Soil losses due to potato and
sugar beet harvesting in NE China.Earth Surface Pro-
cesses and Landforms, 31(8): 1003-1016.
McLean, E. O., 1982. Soil pH and lime requirement. In:
Page et al. (eds) Methods of Soil Analysis, Part 2.
Chemical and microbial properties. 2nd ed. Agronomy
monograph 9. ASA and SSSA, Madison, WI, pp. 199-
224.
Mwango, S.B., Msanya, B.M., Mtakwa, P.W., Kimaro, D.N.,
Deckers, J., Poesen, J., Lilanga, S. and Sanga, R. 2015.
Soil loss due to crop harvesting in Usambara Mountains,
Tanzania: the case of carrot, onion and potato. Interna-
tional Journal of Plant and Soil Science 4 (1): 18–28.
Nelson, D. W., Sommers, L. E., 1982. Total carbon, organic
carbon, organic matter. In Page et al. Eds. Methods of
soil analysis (Part 2) Agronomy monograph 9. Soil Sci-
ence Society of America. pp. 539-579.
Olsen, S. R., Sommers, L. E., 1982. Phosphorus. In: Page,
AL, editor. Methods of soil analysis: chemical and mi-
crobiological properties. Madison (WI): American Soci-
ety of Agronomy p. 403-427.
Oshunsanya, S. O., Samson, V.M., 2019. Estimation of soil
loss due to cassava harvesting in Ibadan, Nige-
ria.Proccedings of the 43rd Annual Conference of the
Soil Science Society Nigeria, Federal University of Ag-
riculture, Makurdi, Nigeria; pp. 713-718.
Oshunsanya, S. O., Yu, H., Li, Y., 2018a. Soil loss due to
root crop harvesting increases with tillage operations.
Soil and Tillage Research 181: 93-101.
Oshunsanya, S. O., Yu, H. Q., Li, Y., Saggar, S., 2018b.
Root hairs and cortex contribute to soil loss due to root
crop harvesting. Catena 174: 514-523.
Parlak, M., Cicek, G. and Blano-Canqui, H. 2018. Celery
harvesting causes losses of soil: a case study in Turkey.
Soil Tillage Research 180: 204–209.
Parlak, M., Palta, C., Yokus, S., Blanco-Canqui, H. and
Carkaci, D.A. 2016. Soil losses due to carrot harvesting
in south central Turkey.Catena 140: 24–30.
Poesen, J. 2018. Soil erosion in the anthropocene: research
needs. Earth Surface Processes Landforms 43: 64–84.
Poesen, J., Verstraeten, G., Soenens, R., Seynaeve, L., 2001.
Soil losses due to harvesting of chicory roots and sugar
beet: an underrated geomorphic process.Catena 43: 35–
47.
Rhodes, J. D., 1982. Cation exchange capacity. In methods
of soil analysis, Part 2: Chemical microbiological prop-
erties. 2ndedn (ed. A. L. Page). American Society of
Agronomy, Madison, Wisconsin, pp. 149-157.
Ruysschaert, G., Poesen, J., Verstraeten, G. and Govers, G.
2004. Soil loss due to crop harvesting: significance and
determining factors. Progress in Physical Geography 28:
467–501.
Samson and Ityavnongo NJSS 31 (3) 2021 42-47

47
Ruysschaert, G., Poesen, J.,Wauters, A., Govers, G. and Ver-
straeten, G. 2007. Factors controlling soil loss during
sugar beet harvesting at the field plot scale in Belgium.
European Journal of Soil Science 58: 1400–1409.
Sumithra, R., Thushyanthy, M. and Srivaratharasan, T.
2013.Assessment of soil loss and nutrient depletion due
to cassava harvesting: a case study from low input tradi-
tional agriculture. International Soil and W ater Conser-
vation Research 1(2): 72-79.
Walkley, A., Black, C. A., 1934. An examination of the dif-
ferent method for determining soil organic matter and a
proposed modification to the chronic titration meth-
od.Soil Science 37: 29-38.
Yu, H., Li, Y., Chappel, A., Poesen, J., 2016. Soil nutrient
loss due to tuber crop harvesting and its environmental
impact in the north China plain.Journal of Integrative
Agriculture 15, 1612-1624. DOI: 10.1016/S2095-3119
(15)61268-0.