A member of CGIAR consortium www.iita.org Evaluating yield gaps in cassava production systems in Zambia Nhamo NHAMO (PhD) Cassava Agronomist The World Congress on Root an Tuber Crops, 18-22 January, 2016 Nanning, Guangxi, China
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Evaluating yield gaps in cassava
production systems in Zambia
Nhamo NHAMO (PhD)
Cassava Agronomist
The World Congress on Root an Tuber Crops,
18-22 January, 2016
Nanning, Guangxi, China
A member of CGIAR consortium www.iita.org
Outline
1. Yield gaps in cassava systems
2. Observations from cassava production
systems in Zambia
3. Improved Cassava production practices
4. Focusing on the gains to close gaps
5. Conclusions
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Cassava is food
Cassava
processing
for food:
Peeling and
pounding for
household
food
3
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Yield gaps…1
Yield gap is the difference between the
farmers’ average crop yield and the
biologically and climatically attainable yield
for a particular area
• Yield determining factors (radiation & temp)
• Yield limiting factors (soil water & nutrition)
Overall cassava production is linked
to the size and nature of gaps in the
system4
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5Lobell et al. 2009; Nhamo et al. 2014
The process:
1. Simulation modeling
2. On-station trials
3. Diagnostic surveys
4. On-farm research
5. Farmer driven research
An illustration of yield
gaps at different levels
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Farmer vs Research plots
6Groundnut
OkraCassavaSweetpotato
Cassava and maize intercrop
(i) (i i)
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Why work on yield gaps?
• Adequately describe
cassava production systems
• Analyse yields in relation to
production factors
• Design interventions for
improved cassava systems
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Understanding farmers’ practices
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Current practices
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Cropping patterns
District
All
Serenje Samfya Mansa Kasama Kaoma
Mono cropping (%) 71 51 42 50 65 56
Mixed cropping (%) 29 49 58 50 35 44Weeding method
Only manual 98 100 100 99 100 99
Only herbicides 0 0 0 0 0 0
Manual+herbicides 0 0 0 0 0 0
Other 0 0 0 0 0 0
Types of fertilisers
No fertiliser 92 100 79 95 100 93
Organic fertiliser 6 0 1 0 0 1
Chemical fertiliser 0 0 0 0 0 0
Combination of
organic and
chemical fertilisers 1 0 3 4 0 2
Mixed cropping
is common
practise
Low to no
external
agrochemical
inputs
Source: IITA farmers surveys
Manual
weeding
methods
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Cassava intercropping
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Cropping patterns
Camp
AllKapyata Bahati Chisunka
Mono cropping (%) 40 20 40 33
Mixed cropping (%) 60 80 60 67
Maize (%) 20 20 20 20Millet (%) 0 0 0 0
Cotton (%) 0 0 0 0
Groundnuts (%) 30 20 30 27Cowpea (%) 0 0 0 0
Sweet potatoes (%) 10 40 10 20Potato (%) 0 0 0 0
Vegetables (%) 0 0 0 0
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Cassava lessons
• 1960s +i. Cassava was introduced for poor
farmers to avert persistent droughts
ii. Limited support from the government
»e.g. extension training does not include
cassava production practices
• 2000 +i. Recognition of importance is beginning
to increase
ii. Value chain and Markets not devoloped
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Soils characteristics
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Site
pH
(CaCl2)
P
ppm
Ca
ppm
Mg
ppm
K
ppm
OC
%
N
%
CEC
Cmol+kg
Kaoma 4.5 5 180 10 19 0.08 0.04 1.87
Kasama 4.1 4 60 20 137 0.65 0.03 7.17
Mansa 4.2 6 100 40 116 0.20 0.02 6.31
Serenje 4.2 23 70 40 36 0.37 0.02 1.89
• Acidity linked to highly weathered
soils and rainfall
• Low soil organic matter and CEC
• 2/4 sites deficient in K
• P deficiency at all sites except Serenje
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Rainfall patterns
13
0
50
100
150
200
250
Oct-13 Nov-13 Dec-13 Jan-14 Feb-14 Mar-14 Apr-14
Rain
fall (
mm
)
Time (Months)
Total rainfall = 1020 mm
• Rain falls for about 6 months per year
• Large storms often short duration
• Uneven distribution during the season –
midseason droughts
Total rainfall
is probably
not a major
bottleneck
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Temperature extremes
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0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
MinTemp oC
MaxTempoC
High probability of minimum temperatures
below 12 oC between May and August
Loss of leaves due to
dry and cold weather
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Sources of Yield Gains
• Moving from blanket to site-specificity
• Effective use of fertilizer in combination with
other technologies
• Weed management practices that explore
synergies with other technologies
• Future role of improved varieties which have
characteristics that address more than one
constraint
• Yield targeting under improved nutrient, water
and weed management15
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Focusing on the gains to
close gaps
Agronomy research
1. Cassava intensification options
2. Weather/Climate patterns
3. Extension messages on management
– Crop response to improved management
• Fertilizer inputs
• Weed management
• Time of planting
• Planting population
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Yields response to
management
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Means and 95% C.I. of R_Yld for W_man
1 2 3 4 50
5
10
15
20
R_
Yld
W_man
Means and 95% C.I. of R_Yld for Popn
1 20
4
8
12
16
R_
Yld
Popn
SED 1.7863
1=Clean weeding 2=Farmer’s practice
3. Delayed first weeding 4=No weeding
5=Manual and chemical
Means and 95% C.I. of Rt_yld for fert
F1 F2 F30
10
20
30
Rt_
yld
fert
F1 = No fertilizer F2 = 40N 40P 40K
F3 = 120N 80P 80K
SED 1.2416
P1 = 10000 ha-1 P2 = 20000 ha-1
SED 3.2442
Means and 95% C.I. of R_Yld for Time
1 2 30
8
16
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R_Y
ld
Time
Planting times
1. December 2. January 3. February
Significant yield loss
due to delayed
planting, no weeding
and higher plant
populations.
Significant yield
gains due fertilizer
inputs and related
management.
Timing important for
climate extremes,
weeding and plant
populations for
resource
management.
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Cassava Root Yield gains
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Practice Yield gain
(t/ha)
Relative
gain (%)
Fertilizer 7-18 35%
Weed Management 7-17 63%
Timing of planting 7-10 83%
Plant population 3-5 48%
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Re-designing Cassava
production system
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Cutting trees
Burning organics
Crop mixes
Rainfall
patterns;
TemperatureSoil quality;
organic
matter loss; Crop productivity
goes down
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Conclusions
Options for intensification
• Fertilizer application supports high
yields in cassava systems
• Intensification requires efficient
utilization of fertility input for
sustainability
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Weed management in cassava
• Large differences exist between
weeded and unweeded plots (4-17
t/ha)
• High planting density did not reduce
weed biomass in cassava plots
• Manual and chemical weed
management practices need to be
evaluated
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Timing and plant populations
• Cassava root yields responded to
time of planting and planting
populations.
• Management of the growing
season is important for cassava
bulking especially in Zambia
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Next steps…
• Data on crop response important for:
• developing decision support tools for
farmers and extension personnel
• extension messages for specific
environments
• Intensification options and stepwise
adoption of technologies
• Farm budgets for large scale farmers
• Markets and market linkages
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Acknowledgements
• The African Development Bank (AfDB)
• IITA Team and Partners
• Farmers, women and youth
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