Mr Taiwo Michael Agbede, Rufus Giwa Polytechnic, Nigeria. Global Symposium on Soil Erosion (GSER19), 15 - 17 May 2019 at FAO HQ.

1. Effects of biochar on soil properties and
erosion potential in a degraded sandy soil
Taiwo Michael Agbede - Department of Crop,
Soil and Pest Management Technology, Rufus
Giwa Polytechnic, P.M.B. 1019, Owo, Ondo
State, Nigeria
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2. INTRODUCTION
• Intensive, long-term cultivation of sandy soils often
results in their degradation, which includes soil
acidification, soil organic matter (SOM) depletion
and severe soil erosion and leaching.
• The decrease in soil organic carbon (SOC) caused
by long-term cultivation decreases the aggregate
stability of the soil and increases its erosion
potential.
• Therefore, the effective maintenance of SOM in
degraded soils can help preserve soil fertility and
reduce erosion susceptibility by promoting soil
aggregation stability, and improving hydraulic
conductivity and water retention ability.
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3. • An alternative to the use of ordinary degradable
organic manures is the use of more stable
compounds such as biochar.
• Biochar, a carbon-rich material obtained from
heating organic biomass under limited oxygen
conditions appears to be a more stable source of
carbon and it remains in the soil for hundreds or
even thousands of years.
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4. • Little research has been conducted on the effects of
biochar on physico-chemical properties of sandy soil and
potential to erosion control.
• Where such studies were performed, they were pot
experiments in a greenhouse and not field experiment.
• Researchers had suggested that future research need to
focus on testing biochar amendments in experimental
plots and under field conditions and achieving a better
understanding of the physical and chemical properties of
biochar surfaces.
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5. OBJECTIVES OF THE STUDY
• The objectives of this study were:
(1) to evaluate the effects of wood biochar on the
physicochemical properties and erosion potential of a
degraded sandy soil, and
(2) to assess the relationships between soil properties
and soil erosion potential.
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6. MATERIALS AND METHODS
• The experiments were carried out at the Teaching and
Research Farm of Rufus Giwa Polytechnic, Owo (latitude 70
12’N, longitude 50 35’E), Ondo State, southwestern Nigeria.
• The soil at the experimental site belongs to an Alfisol
classified as Oxic Tropuldalf or Luvisol, derived from
quartzite, gneiss and schist.
• The trials were conducted for two cropping seasons of 2017
and 2018 on the same site.
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7. • The experiment each year consisted of four treatments:
• (a) control, natural soil fertility (NSF),
• (b) biochar (B) at 10 t ha-1;
• (c) biochar (B) at 20 t ha-1 and
• (d) biochar (B) at 30 t ha-1.
• The four treatments were laid out in a randomized
complete block design with three replications.
• Biochar used was from hardwoods.
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8. • The biochar was produced at a pyrolysis temperature of
700°C based on the recommendation of Lehmann (2007).
• After pyrolysis, the biochar was ground and sieved
through a 2 mm sieve.
• The biochar (B) was weighed and spread uniformly over
the soil on the plots according to the required rates ( 0, 10,
20 and 30 t ha-1).
• The biochar was incorporated into the soil to the depth of
approximately 10 cm and then left in the soil for 9 months
in each year.
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9. • Before the commencement of the experiment in
2017, soil samples and biochar used for the
experiment were analysed to determine its chemical
composition.
• In 2017 and 2018 at 9 months after biochar
incorporation, composite soil samples were also
collected on plot basis for physical and chemical
analysis.
• Physical properties measured include bulk density
(determined by the core method), porosity,
penetration resistance, moisture content, saturated
hydraulic conductivity, aggregate stability and soil
losses.
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10. • Soil samples were collected randomly per plot at harvest in
2017 and 2018 for routine chemical analysis, as described
by Carter and Gregorich (2007).
• Data collected from each experiment were subjected to
mean separation analysis using the 1-way ANOVA test at a
significance of p = 0.05.
• The differences between mean values were identified using
Duncan's multiple range test. Pearson's correlation
coefficients were calculated to determine how the soil
properties are related.
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11. 11
Experimental site and biochar

12. 12
Experimental site and biochar

13. 13
The biochar being applied to experimental plots

14. 14
Biochar produced from hardwoods
by heat treatment

15. RESULTS
Table 1. Basic properties of the experimental site and the biochar prior to
experimentation in 2017
ND; Not determined
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Property Soil Biochar
Sand (%) 92.4 ND
Silt (%) 2.8 ND
Clay (%) 4.8 ND
Textural class Sand ND
Bulk density (Mg m-3) 1.58 0.60
pH (water) 5.6 7.62
Ash ND 0.028
Organic carbon (%) 0.74 520.3
Total N (%) 0.10 0.65
C/N 7.4 800.5
Available P (mg kg-1) 2.68 0.36
Exchangeable K (cmol kg-1) 0.12 1.75
Exchangeable Ca (cmol kg-1) 3.1 4.51
Exchangeable Mg (cmol kg-1) 0.98 7.75
Copper (%) ND 0.013
Manganese (%) ND 0.068
Sulphur (%) ND 0.091
Zinc (%) ND 0.008
Sodium (%) ND 0.21

16. Table 2. The physical properties of biochar-amended soil at the end of incorporation time
(pooled data of 2017 and 2018
Biochar
(t ha-1)
Bd
(Mg m-3)
Porosity
(%)
PR
(kg cm-2)
MC
(%)
Ksat
(cm day-1)
MWD
(mm)
SL
(cm)
SL
(kg ha-1)
0 1.54a 41.9d 16.5a 11.3d 1.64d 1.16d 2.11 324.9
10 1.41b 46.8c 11.2b 13.3c 2.05c 1.53c 1.58 222.8
20 1.28c 51.7b 6.7c 16.1b 2.81b 1.80b 1.06 135.7
30 1.06d 60.0a 2.8d 17.6a 3.56a 2.09a 0.54 57.2
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Bd: bulk density; PR: penetration resistance; MC: moisture content; Ksat: saturated hydraulic
conductivity; MWD: mean weight diameter of soil aggregate; SL: soil loss.
Values followed by similar letters under the same column are not significantly different at p =
0.05 according to Duncan’s multiple range test.

17. Table 3. The chemical properties of biochar-amended soil at the end of
incorporation time (pooled data of 2017 and 2018
Biochar
(t ha-1)
pH
(water)
OC
(%)
N
(%)
P
mg kg-1
K
(cmol kg-1)
Ca
(cmol kg-1)
Mg
(cmol kg-1)
0 5.63c 0.61d 0.08d 1.91d 0.10d 1.62d 0.35d
10 6.25b 1.15c 0.10c 2.26c 0.21c 3.05c 0.77c
20 6.85a 1.25b 0.12b 2.67b 0.27b 3.42b 0.89b
30 7.00a 1.36a 0.14a 2.90a 0.33a 4.33a 1.03a
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Values followed by similar letters under the same column are not significantly different at p =
0.05 according to Duncan’s multiple range test.

18. Table 4. Pearson’s correlation coefficients among soil properties at the end of
incorporation time (after 9 months)
pH OC N P K Ca Mg Bd PO PR MC Ksat MWD SL
pH 1.00
OC 0.95* 1.00
N 0.97* 0.91* 1.00
P 0.99** 0.92* 0.99** 1.00
K 0.98* 0.96* 0.98* 0.98* 1.00
Ca 0.95* 0.96* 0.97* 0.96* 0.99** 1.00
Mg 0.97* 0.99** 0.95* 0.95* 0.98* 0.98* 1.00
Bd -0.93* -0.86* -0.99** -0.97* -0.96* -0.95* -0.91* 1.00
PO 0.93* 0.86* 0.99** 0.97* 0.96* 0.95* 0.91* -1.00** 1.00
PR -0.98* -0.93* -0.99** -0.99** -0.99** -0.98* -0.96* 0.98* -0.97* 1.00
MC 0.98* 0.90* 0.99** 0.99** 0.98* 0.95* 0.94* -0.97* 0.97* -0.99** 1.00
Ksat 0.98* 0.92* 0.99** 0.99** 0.99** 0.97* 0.95* -0.98* 0.98* -0.99** 0.99** 1.00
MWD 0.95* 0.86* 0.99** 0.98* 0.96* 0.94* 0.91* -0.99** 0.99** -0.98* 0.99** 0.99** 1.00
SL -0.96* -0.99** -0.93* -0.94* -0.98* -0.98* -0.99** 0.89* -0.89* 0.95* -0.93* -0.94* -0.89* 1.00
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OC: organic carbon; N: nitrogen; P: phosphorus; K: potassium; Ca: calcium, Mg: magnesium; Bd: bulk density; PO: porosity; PR:
penetration resistance; MC: moisture content; Ksat: saturated hydraulic conductivity; MWD: mean weight diameter of soil
aggregate; SL: soil loss; *: p < 0.05; **: p < 0.01

19. CONCLUSIONS
• Biochar prepared from the waste wood of trees through
pyrolysis is an acid-neutralizing material for severely
degraded soils, and is a potential source of nutrients. The
persistent characteristics of the biochar ensure long-term
benefits for the soils.
• Our field experiments showed that wood biochar not only
improved the chemical properties, but also improved the
physical properties of the soil, such as bulk density,
porosity, penetration resistance, moisture content,
hydraulic conductivity, aggregate stability, and erosion
resistance.
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• These results suggest that the addition of wood biochar
effectively improved poor soil characteristics in severely
degraded sandy soil, and reduced soil losses. The results
of this study could be used to avoid rapid soil degradation
and soil loss in tropical and subtropical regions.

21. • THANK YOU FOR LISTENING.
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