Evaluation of Agronomic practices on growth, yield of cassava and soil physical properties in southwestern Nigeria

1. A research activity update on
Evaluation of agronomic practices on growth, yield of cassava and
soil physical properties in southwestern Nigeria
Olabisi Omolara Onasanya
A PhD Project within the Africa Cassava Agronomy Initiative on the “Best
Planting Practices” use case

2. Overall Objective
• Provide site-specific recommendations on agronomic practices in cassava systems to
conserve soil while maintaining high cassava yields in Nigeria.
Introduction
• Tillage is the physical, chemical or biological soil manipulation to optimize conditions for
seed germination, emergence and seedling establishment, BUT
• Tillage may either be beneficial or detrimental to the soil over time
• Hence, it is important to look into improved agronomic practices in combination with
tillage that will best conserve the soil under cassava systems

3. Agronomic practices and cassava growth, root yield and quality
• To investigate the effects of basic tillage(ploughing), shaping the soil
surface (ridging), weed control and fertilizer application on the
establishment, growth, root yield and quality of cassava
Tillage intensity and soil aggregate stability
• To evaluate the impact of tillage intensity on soil aggregate stability, soil
C and N in particle size fractions and determine their relationship with
cassava yield
Tillage Intensity and least limiting water range
• To determine the effect of tillage on soil strength, compaction and the
least limiting water range and relationship between physical- hydraulic
properties and cassava root yield
Specific objectives

4. Experimental Setup
• Study in Oyo and Ogun State, Nigeria
over 2 years (2017 and 2018)
• Researcher Managed Trials (RMTs)
established in Saki, Ido and Odeda
Local government areas (2nd year
ongoing)

5. Experimental design and layout

6. Climatic and soil variations of sites where Researcher Managed Trials (2017) were installed
Location
Soil depth
(cm)
pH O.C Total N P (ppm) % Sand % Silt % Clay
Ca Mg K Na
C mol/kg
Odeda 0-20 6.7 0.88 0.079 4.35 65 17 18 3.85 1.5 0.16 0.12
20-50 6.7 0.54 0.037 1.67 66 18 16 1.69 0.67 0.08 0.13
Ido 0-20 6.6 0.92 0.081 2.14 65 13 22 3.89 1.29 0.19 0.06
20-50 6.5 0.64 0.06 6.57 65 15 20 3.02 1.03 0.14 0.07
Saki 0-20 6.6 0.36 0.038 2.3 65 17 18 1.64 0.5 0.08 0.09
20-50 6.5 0.44 0.036 2.14 60 18 22 1.78 0.57 0.1 0.2
Local Government
Area
Agro ecological zone Parent
material
* Average annual
temperature (OC)
*Average annual rainfall
(mm)
Ido Southern guinea
savannah
Basement
complex
22.9 – 24.4 1136 - 1341
Odeda Derived savannah Sandstone 26.1 – 27.8 1136 - 1341
Saki Derived savannah Basement
complex
22.9 – 24.4 934 - 1136
* data from year 1950- 2000

7. Task 1: Cassava measurements to address the effects of agronomic practices
• Sprout count
• Plant height
• Number of main stems per plant
• Number of leaf (scars and alive) per plant
• Light interception: 12 & 24
• Fresh root mass per plot
• Root number and diameter
• Dry matter content of roots
• Number of bad (rot) roots per plot
• Starch content
4, 8, 12, 16, 24 & 48
weeks after planting
48 weeks
(harvest)

8. Germinationcount
Zero plough
Single plough
flat ridge flat ridge
Year 2: 2018Year 1: 2017 p.value
ds$basicTillage 0.00000
ds$soilShape 0.00001
Year 0.18463
No significant interactions
Effect of tillage intensity on cassava germination at 4 weeks after planting

9. Effect of tillage intensity on cassava germination at 4 weeks after planting by experimental sites

10. p.value
Treatment 0.01
Location 0.02
Treatment:Location 0.98072
Mean Group
Ido 185.97 A
Odeda 92.47 B
Saki 46.68 B
Treatment Mean Group
SP-RG-HB-F1 125.80 A
SP-RG-FC-F1 124.31 AB
SP-FL-FC-F1 120.99 ABC
SP-FL-HB-F1 117.84 ABC
ZP-RG-HB-F1 115.49 ABC
ZP-RG-FC-F1 115.41 ABC
SP-RG-HB-F0 114.69 ABC
ZP-FL-HB-F1 112.80 ABC
SP-RG-FC-F0 111.03 ABCD
SP-FL-HB-F0 110.99 ABCD
ZP-FL-FC-F1 105.56 ABCDE
ZP-RG-HB-F0 102.56 BCDE
SP-FL-FC-F0 101.59 CDE
ZP-RG-FC-F0 99.78 CDE
ZP-FL-FC-F0 88.76 DE
ZP-FL-HB-F0 82.94 E
Response and variation of cassava plant height (cm) to treatment
SP: Single Plough
ZP: Zero Plough
FL: Flat
RG: Ridge
HB: Herbicide control
FC: Farmer’s control (hoe weeding)
F1: Fertilized
F0:Unfertilized
KEYS

11. Cassava height progression weeks after planting by experimental sites

12. Treatment Mean Group
1 SinglePlough:Ridge:Farmerschoice:Fertilized 22.36 A
2 SinglePlough:Ridge:Herbicide:Unfertilized 18.51 AB
3 SinglePlough:Ridge:Herbicide:Fertilized 18.42 AB
4 SinglePlough:Flat:Farmerschoice:Fertilized 16.95 BC
5 SinglePlough:Ridge:Farmerschoice:Unfertilized 16.71 BCD
6 SinglePlough:Flat:Farmerschoice:Unfertilized 15.47 BCDE
7 ZeroPlough:Ridge:Herbicide:Fertilized 14.28 BCDEF
8 ZeroPlough:Ridge:Farmerschoice:Unfertilized 14.06 BCDEF
9 SinglePlough:Flat:Herbicide:Unfertilized 13.81 CDEF
10 ZeroPlough:Ridge:Farmerschoice:Fertilized 13.39 CDEF
11 SinglePlough:Flat:Herbicide:Fertilized 12.63 DEF
12 ZeroPlough:Flat:Herbicide:Fertilized 11.38 EF
13 ZeroPlough:Flat:Farmerschoice:Fertilized 10.13 FG
14 ZeroPlough:Ridge:Herbicide:Unfertilized 10.13 FG
15 ZeroPlough:Flat:Farmerschoice:Unfertilized 9.78 FG
16 ZeroPlough:Flat:Herbicide:Unfertilized 5.99 G
Treatment effects on cassava root yield (t/ha)

13. Cassava root yield (t/ha) relative to treatment by experimental sites

14. • The sieves were immersed in water and moved vertically by 2 cm height
amplitude at 60 oscillations per minute
• The soil fraction left on each sieve was recovered, dried to 0% moisture and
weighed to calculate the mean weight diameter (MWD)Soil samples were air-dried and passed
through an 8 mm sieve before wet sieving
with stacks of sieves (2 mm, 0.25 mm, and
0.053 mm)
Task 2: Evaluating the effect of basic tillage and soil shaping on aggregate stability
Van Bavel, 1949MWD = σ𝑖
𝑛
𝑋𝑖𝑤𝑖
Xi= mean diameter of each size fraction
Wi = proportion of the total sample weight corresponding size fraction

15. Mean weight diameter in response to tillage intensity as growth progresses

16. Soil aggregate size distribution after being subjected to tillage intensities
At establishment
At harvest
Mass(g)
Mass(g)Tillage intensities
Tillage intensities
SP: Single plough
ZP: Zero plough
FL: Flat
RG: Ridge

17. At establishment
At harvest
Carboncontent(%)Carboncontent(%)
Nitrogencontent(%)Nitrogencontent(%)
At establishment
At harvest
Carbon and nitrogen content (%) in individual soil fraction at establishment and harvest

18. Task 3: Observations to study the effect of tillage intensity on soil strength, compaction and cassava
yield
• Penetrologger is used to measure the resistance
of soil to penetration as a proxy for soil strength
and compaction.
• Soil resistance to penetration is dependent on
soil moisture content.

19. 0 -10 cm 10 -20 cm 20 -30 cm
OdedaIdoSaki
Changes in penetration resistance with depth weeks after planting following different tillage intensities
SP: single plough
ZP: zero plough
FL: flat
RG: ridge

20. Preliminary conclusions…………
• Zero plough reduced germination count in both years of experiment, as well as planting in
flat land.
• Basic tillage influenced fertilizer response to root yield.
• Across locations, zero plough increased mean weight diameter and decreased resistance to
penetration
• Treatment response to yield was location dependent as inherent soil properties play a
distinct role

21. THANK YOU
FOR
LISTENING