Transcript Solving Africa’s Weed Problem: Increasing Crop Production & Improving the Lives of Women Leonard Gianessi, CropLife Foundation.

Solving Africa’s Weed Problem:
Increasing Crop Production &
Improving the Lives of Women
Leonard Gianessi, CropLife Foundation
Sub-Saharan Africa
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43 Countries
700 Million People
180 Million Farms
170 Million Crop
Hectares
Typical Smallholder Farm
1 hectare: 2.5 Acres (1 U.S. city block)
Maize
Sorghum
Cassava
Maize
Home
garden
Maize
Yams
Cotton
GroundCowpea
nuts
Sub-Saharan
Africa: Crop Production
million tons/year
Maize
43
Rice
14
Groundnuts
8
Cassava
118
Sorghum
20
FAO, 2005
Crop Yields (Tons/hectare)
Africa
Global
Maize
1.6
4.5
Rice
1.9
3.8
Sorghum
.9
1.3
Groundnuts
.7
1.4
FAO
African Yields (Tons/hectare)
Experimental Plots
Average Farmer
Maize
Rice
8
4
1-2
1
DeVries and Toenniessen, 2001
Tittonel, et al, 2007
Optimal Yields on
Experimental Plots
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Plant at Right Time
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Weed at Right Time
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Fertilize at Right Time
Farmers in Africa will not obtain the
optimum from their crops, land and
other investments in crop production if
there is no improvement in their
traditional methods of weed control.
Akobundu, 1991
Weeds in Africa
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Soils contain 100 to 300 million weed
seeds/hectare
Seeds can remain dormant in the soil for
decades
Unweeded plots produce 25 Tons/Hectare
of weeds
Adigun, et al, 1991
Striga in Sorghum Field
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50,000-200,000 seeds/plant
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Seeds can live in soil for 20
years
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250,000 emerged weed
seedlings/hectare
AATF, 2006
Weedy Maize Field
Weeds compete
with crops for
space, nutrients,
sunlight and
moisture reducing
crop yields.
Maize Yield Reduced 90%
Weeds Need to be Removed
Before Planting a Field
MAIZE
WEEDY FIELD
MAIZE
Removing Weeds Before Planting
with Hand Hoes
126 hours/hectare
Enete, Nweke, & Tollens, 2002
Weeds Need to be Removed
During the Growing Season
30-40% Yield Loss
Handweeding is the
Predominant Weed Control
Practice in Sub-Saharan Africa
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50-70% of the
labor in crop
production is
spent weeding.
Chikoye, et al, 2007
Female Labor Contribution to
Weeding- Nigeria
Maize
Cassava
Cowpeas
Rice
%
95
90
100
80
Ukeje, 2004
Handhoeing Permanently
Deforms Women’s Spines
To weed one
hectare a
woman walks
10 kilometers in
a stooped
position.
Hours of In-Crop Handweeding
Required for Optimal Yields
Groundnuts
Cassava
Maize
Sorghum
(Hours/Hectare)
378
270
276
150
Akobundu, 1987
Weed Free Period Required for
Optimal Yields
Days After Planting
Cassava
Maize
Rice
Sorghum
84
56
42
35
Akobundu, 1987
Nigerian Cotton
Weed Control Experiment
# of Weedings
Yield kg/ha
0
73
1
249
2
401
3
549
Maize Yield: Malawi
Yield
One week delay in 1st weeding
Two week delay in 2nd weeding
- 33%
- 25%
Orr, Mwale and Saiti, 2002
Labor “Bottleneck”
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Several different crops are planted in
sequence on each farm.
Weeding of crop planted first is often
delayed by need to plant the next crop.
Weeding of crops is not done at optimal
time.
Farmer practice: partial weeding.
Constraints on Timely
Hand-Weeding
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Women can be too
tired or sick (malaria)
Fields can be muddy
Competing time
demands: child care
Pregnancy
Male Labor for Weeding
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Becoming Scarce
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Off-Farm Employment
Urban Migration
AIDS
WEEDY
WEEDS
REMOVED
COTTON
PLANTS
Cotton crop weeded after weeds had
reduced potential yield by 75%.
In Malawi, one-third of the area
planted to maize by smallholders
is either left unweeded or weeded
after the critical six weeks.
Orr, Mwale & Saiti, 2002
In Zimbabwe, one third of the
maize is planted late because of
labor constraints with a yield loss
of up to 75% in late planted fields.
Byerlee & Helsey, 1996
In Zimbabwe, 21% of cotton
farmers abandon more than
20% of their cropped area each
year as a result of weed
infestations.
Mavudzi, et al, 2001
One effect of labor shortage is
that more land on the farm is
left fallow. The area cultivated
is often reduced by 50%.
Bishop-Sambrook, 2003
In Africa, yield losses due to weeds range
from 25% to total crop failure.
The majority of farmers in Ghana identify
weeding as the major constraint in their
farming systems.
Vissoh, et al, 2004
Sub-Saharan Africa
Inorganic Fertilizer Use
Farmers Using
Application Rate
Recommended Rates
5%
<50 kg/ha
250-350 kg/ha
Dar & Twomlow, 2004
ICRISAT
Given the strategic importance of fertilizer to end hunger, the African Union
member states resolve to increase the level of fertilizer use by 500% by 2015.
Benefits of fertilizer use
dependent on weed control
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Certain weeds absorb nutrients faster
than crops
Without weed control, increased fertilizer
use leads to more weeds
Farmers reluctant to increase fertilizer use
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Increased need for hand weeding
“Labor bottleneck”
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Labor not available for applying fertilizers
Fertilizer Experiment: Wheat,
Ethiopia
Nitrogen
(kg/ha)
0
46
92
Weeds
(million/hectare)
1.9
2.2
2.5
Workdays
Weeding/hectare
88
92
107
Tanner, Gorfu & Taa, 1993
Fertilizer application increases the
labor required during peak
season by 64 hours per hectare in
sorghum which includes
increased weeding time.
Wubeneh & Sanders, 2006
The Parasitic
Weed Striga
STRIGA SEED
Striga germinates after
being stimulated by crop
roots, and then grows
toward the crop roots,
attaches, and sucks
nutrients from the crop.
Striga also poisons the
crop.
MAIZE ROOT
Gressel
Striga in Maize Field
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Damage to crop done below ground
Damage cannot be prevented by hand-pulling
10-70% yield loss
Gressel, et al, 2004
Striga Impacts
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Infests 22 to 40 million hectares of
farmland.
30-40% of the total farmlands have been
abandoned to sorghum or maize
cultivation in some African countries.
A loss of 8 million tons of crops per year
due to striga.
Gressel, et al 2004
Mutengwa, et al, 1999
Typical Smallholder Farm
Impact of Weeds
Weeded late
Striga
Weeded late
Weeded late
Weeded late
Maize
Sorghum
Cassava
Maize
Home
garden
Yams
Cotton
GroundCowpea
nuts
Maize
Striga
Abandoned
Planted late
No Fertilizer Application to Any Field
Not planted
The Spraying of Chemical Herbicides
is an Alternative to Handweeding
Killing Weeds Before Planting
with Herbicide Sprays
Weeds Killed Before Planting
With Herbicides
-124 hours/hectare Handweeding
+2 hours/hectare Herbicide Spray
Gressel, Piesse
& Thirtle, 2006
Residual Power of
Chemical Herbicides
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Some chemicals
can be sprayed
on the soil.
They stay active
in the soil for
weeks.
Germinating
weed seeds are
killed.
Cotton Experiment:
4 Weeks After Herbicide Spray
Untreated
Herbicide
Treated
-254 hours/hectare Handweeding
+1.5 kg/hectare of Chemical
Lagoke, et al, 1992
Herbicide Experiment: Kenya
Maize Yields +53%
Bean Yields +94%
Weedy
Herbicide Treated
Kibata, et al, 2002
Sorghum Weed Control
Experiment: Nigeria
5000
4500
4000
3500
Yield 3000
(kg/ha) 2500
2000
1500
1000
500
0
Weedy Check
Hoe-Weeded
Three Times
Preemergence
Herbicides
Ishaya, et al, 2007
Striga Control with HerbicideTreated Maize Seed
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30g of herbicide are coated onto seed
used to plant 1 hectare.
Striga is killed when it attaches to the
maize root.
The herbicide diffuses into the soil and
kills ungerminated striga seeds.
AATF, 2007
Maize with Herbicide on Seeds
for Striga Control
TREATED
Average yield
from herbicidetreated maize
was triple the
untreated.
UNTREATED
Gressel, et al, 2004
Just over 3% of African
smallholder farmers are using
herbicides in their maize fields.
Overfield, et al, 2001
Lack of knowledge is the most limiting factor in
the adoption of herbicide technology in
communal areas of Zimbabwe. There is a need
to train extension workers on herbicide
technology, who would in turn train the farmer.
If the smallholder farmers are given technical
support, they would take advantage of
herbicide technology and improve crop
production.
Makanganise, et al 1999
Training in Herbicide Application
is Necessary
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The incorrect herbicide applied at the
incorrect time and/or rate
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May not work to control weeds
May damage the crop
Herbicide Use in Cotton, 2005
Uganda
Zambia
% Acres
Treated
1
5
Zimbabwe
10
Cameroon
72
International Cotton Advisory Committee, 2005
Cameroon:
Herbicide Use Impact in Cotton
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Reduced labor by 12 days/hectare
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Reduced cost of weeding by 50%
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Increased yield by 400 kg/hectare
Mathews & Clayton, 1999
Maize Experiment: Kenya
“Chemical weeding was one-third of
the cost of two hand-weedings.”
Maina, et al, 2003
Herbicide Experiments:
Kenya & Uganda
“Herbicides can increase the net economic
benefits to farmers cultivating maize by
up to 80%. When this is combined with
their ability to alleviate seasonal and
gender-based labor constraints, their
potential contribution to a more
successful and economically sustainable
farming system is substantial”
Overfield, et al, 2001
“There are more weed scientists
in the state of California than in
all of Africa.”
Akobundu
What is urgently needed is graduate-level education in
weed science (at the masters and doctoral degree levels)
for nationals in the region. There are many U.S.
funded agricultural development projects in SubSaharan Africa with several universities as
contributing institutions. Nearly all of them have
training in agricultural economics, plant breeding, and
agronomy, but hardly any of the projects have included
training in weed science.
Akobundu, 1991
Weeds remain an underestimated crop pest for
which government spending on training,
research and extension is minimal.
In some cases research in weeds is under the
responsibility of researchers in other disciplines
of crop protection. Such set-ups relegate weed
science as a discipline behind the other plant
protection disciplines of entomology and
pathology.
Sibugu, 1997
“On technical grounds, there are no reasons why
herbicides should not be used on most of the
crops grown in developing countries. Largescale producers of commodity crops, such as
coffee, tea, rubber, oil palm, sugar cane,
pineapple, etc., have used herbicides routinely
for many years but chemical weed control has
often barely impinged upon the smallholder
sector.”
Terry, 1996
Women Need Increased
Access to Credit
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Weeding Seen as
Women’s Work
Financial
Resources
Controlled by Men
Africa Weed Control:
Optimal Handweeding
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100 million hectares, 100 million women
400 hours/hectare = 40 billion hours
African Weed Control:
Current Practice
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100 million hectares,
100 million women
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200 hours/hectare
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20 billion hours
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20-100% yield loss
USA Crops
Million Hectares
Maize
38
Wheat
24
Sorghum
3
Soybeans
26
Cotton
4
TOTAL
95
“An agricultural system that condemns a segment
of the citizenry to the drudgery of hand weeding
and ties up a majority of the country’s
economically active population is certainly
preventing the country from advancing its
economy and well-being.”
Akobundu, 1991
CropLife Foundation
African Weed Control Project

Educate policymakers, grant officials
and governments
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Gain funding to improve weed science
education, research and extension
Visit Us At: www.CropLifeFoundation.org