Field research activity update on PhD proposal “Evaluation of agronomic practices on growth, yield of cassava and some physical properties of soils in SW Nigeria” by Omolara Olabisi

1. 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
A research activity update on

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
• Researcher Managed Trials (RMTs) established in Saki,
Ido and Odeda LGAs (1st year ongoing)
• Multi-Location Trials were established on farmers’ field
but with less detailed measurement (2nd year ongoing)
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

5. • RMT: four-factorial split-split-split-plot with a randomized complete block design replicated 3
times
Experimental design and layout of the treatment

6. Cassava measurements to address the effects of agronomic practices
• Sprout count: 2 and 4
• 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
48 (harvest)

7. Preliminary results…
Effect of tillage intensity on cassava germination at 2 weeks after planting by experimental sites
SP: Single Plough
ZP: Zero Plough

8. Treatment effects on number of leaves at 16 weeks after planting
Preliminary results…
Response: number of leaves
Pr(>F)
basic_tillage 0.6292
seed_bed 0.9722
fertilization 0.8919
Location <2e-16 ***
No significant interactions either

9. Treatment effects on plant height at 16 weeks after planting
Preliminary results…
Response: plant height
Pr(>F)
basic_tillage 0.34175
seed_bed 0.42402
fertilization 0.36972
Location < 2e-16 ***
No significant interactions either

10. MWD = ∑ 𝑋𝑖𝑤𝑖%
& Van Bavel, 1949
Evaluating the effect of basic tillage and soil shaping on aggregate stability
Xi= mean diameter of each size fraction
Wi = proportion of the total sample weight corresponding size fraction

11. Effect of basic tillage and soil shaping on mean weight diameter at 8 weeks after cassava planting
Preliminary results…
Pr(>F)
Basic_tillage 0.005112 **
Soil_shaping 0.658898
Location 0.000258 ***
Basic_tillage:Soil_shaping 0.200977
Basic_tillage:Location 0.033402 *
Basic_tillage:Soil_shaping:Location 0.636226
Response: Mean Weight Diameter

12. 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.

13. Preliminary results…(MPa)
Soil resistance to basic and secondary tillage at 16 weeks after planting
No significant interactions
Pr(<F)
Basic Tillage 0.002008**
Seed bed 0.0873767.
Location <2.2e-16****

14. Preliminary conclusions…………
• Zero plough reduced sprout count, but no treatment effects on number of leaves.
• Across locations, zero plough increased mean weight diameter and decreased resistance to
penetration
• I am looking forward to see if the treatments have an effect
on the yield! And if they are related to the soil physical
conditions…

15. THANK YOU
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