Is conservation agriculture a climate-smart option for smallholders
in sub-Saharan Africa?
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Bruelle G. , Naudin K. , Scopel E. , Corbeels M. , Torquebiau E. , Penot E ., Rabeharisoa L. , Mapfumo P. , Tittonell P.
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FOFIFA/CIRAD, DP SPAD, 101
Sub-Saharan Africa faces the challenge of developing a climate-
Antananarivo, Madagascar.
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CIRAD, UPR AÏDA, 34398
Montpellier, France.
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CIRAD, UMR Innovation,
34398 Montpellier, France.
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smart approach that simultaneously ensures food security,
mitigation and adaptation to climate change**. Conservation
Université d’Antananarivo,
agriculture (CA), widely promoted in sub-Saharan Africa, is
LRI, 101 Antananarivo,
Madagascar.
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University of Zimbabwe,
considered as a way to meet these objectives.
SOFESCA, Mt Pleasant,
Harare, Zimbabwe.
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CONSERVATION
AGRICULTURE*
Wageningen University, FSE,
6708 PB Wageningen, the
Netherlands.
What does the scientific literature reflect?
Here are reported evidence from peer-reviewed papers comparing the performances of CA and conventionnal
tillage-based (CV) cropping systems in the context of sub-Saharan Africa.
5 studies
N2O and CO2 emissions either
increase or decrease under CA
compared to CV depending on the
type of crop residue, soil, and
cropping system.
No general conclusion can be drawn from the
results, and all the studies agreed on the necessity
to run experiments on the longer-term and at larger
scale to encompass the variability of soil and crop
types in sub-Saharan Africa.
55 paired CA-CV comparisons
Carbon (C)
accumulation is observed in the top
soil layer (at a maximum of 30 cm
depth) but not in deeper soil layers.
This may not translate into
sustainable forms of C sequestration
(Powlson et al., 2014).
We were unable to distinguish soil C content
changes due to tillage management, soil cover, crop
rotation, or the interaction between these factors.
For a better quantification of the potential of CA to
sequester CA, there is a need to standardize
methodologies (Derpsch et al., 2014).
178 paired CA-CV comparisons
Rainfall changes predictions are
uncertain in Africa**. Our review indicates that CA could express its
potential under:
 A decrease in total seasonal rainfall.
 A delay of the rainy season onset.
 An increase in dry spell frequency within the season.
Under CA practices, the mulch of crop residues held on the soil surface
intercepts rainfall, decreases surface water runoff and limits soil
evaporation. The increase in water infiltration does not necessarily infer
better rainwater use efficiency. It can result in an increase in water drainage.
The impact on water balances and subsequently on yield depends on the
soil characteristics, particularly its water storage capacity in the rooting
zone, the rainfall distribution during the season, and the synchrony between
dry spells (or rainfall episodes) and the crop development stages that
determine the severity of water stress for final crop yield.
7 paired CA-CV comparisons
(5 years and more)
The results are in line with the findings of three
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reviews made in the region (Brouder and Gomez
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-Macpherson, 2014; Giller et al., 2009;
Rusinamhodzi et al., 2011):
 CA has the potential to sustainably increase crop yields
mainly due to the increase in soil fertility over time.
 The long-term improvement of soil fertility is principally
attributed to the retention of mulch on the soil surface.
 Climate conditions are, however, also key determinants of
the time required to observe beneficial impact of CA on
yield. For instance, in a water-limited context, CA alleviates
the soil water stress constraint and allows an immediate
increase in yield.
26 paired CA-CV comparisons
In the short-term, at the field
level, higher economic benefits under CA were
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mainly due to:
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 A decrease in labor.
 An increase in yield.
The decrease in labor was observed regardless the type of cropping
(hand-based, animal-drawn or mechanized). The increases in yield
were attributed to different management or agronomic effects. Lower
economic benefits under CA were caused by different factors:
 The abscence of market for the legumes
 An increase in labor
 A decrease in yield
 An increase in herbicides costs
In the long-term and at the farm-level, results were very variable.
http://agents.cirad.fr/index.php/Guillaume+BRUELLE/poster_CSA_2015
CLIMATE-SMART
AGRICULTURE
**In sub-Saharan Africa, climate projections indicate a
maximum global warming of 2°C at the end of the century
and they suggest steady total seasonal rainfalls but a delay
of the onset of the rainy season and an increase in intensity
and frequency of extreme events such as drought or heavy
rainfall during the rainy season.
(IPCC et al., 2013)
SCAN ME
to obtain the
reference list
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Mulching of crop residue has a key role into the achievement of
climate-smart agriculture. However, retaining a permanent mulch
on the soil surface is very challenging on smallholder farms in SSA.
 CA ability to be climate-smart is very local-specific
 CA is not necessarily climate-smart in sub-Saharan Africa:
 It can contribute to the ‘productivity’ pillar of CSA
 It can contribute to the ‘adaptation’ pillar of CSA
 The contribution to the ‘mitigation’ pillar remains
unanswered
Cropping systems drawings : Team CSIA, UPR 115 AÏDA, CIRAD - http://ur-aida.cirad.fr
© Cirad - Mars 2015 - CSA Global Science Conference - contact : TA C-85/15 - 73 rue Jean-François Breton - 34398 Montpellier Cedex 5 - tel : +33 4 67 61 57 06 / [email protected]
*FAO definition
http://www.fao.org/ag/ca/