1. “Dryland Systems”
Key tradeoffs questions and
tools for CRP1.1
Anthony M. Whitbread
Crop Production Systems in the
Tropics
University of Göttingen,
Germany
W. Payne (ICARDA), T. Gerik (TA&M), D. White
(CSIRO), P. Lecomte (UMR-SELMET), H. Belhouchette
(CIHEAM-IAMM), G. Hammer (QCCA)

2. Integrated Agricultural Production Systems for
Improved Food Security and Livelihoods in Dry Areas
“Dryland Systems”
Dryland Systems targets the
poor and highly vulnerable
populations of dry areas in
developing countries and the
agricultural production
systems on which they depend
for food and livelihoods

3. Dryland Systems- key features
• 65 % of the worlds agricultural lands fall
into the category of drylands
• The majority of the poorest people live in
semi-arid areas.
• Mixed farming systems
• High climate variability and, in-
general, high vulnerability to changes in
climate.
• Already extensive degradation
• Systems analysis needs

4. Targets 2 Strategic Research Themes..
production systems where:
 Reduced vulnerability and
increased resilience to
shocks (SRT2)
 Sustainable intensification
to reduce food security
and generate income
(SRT3)

6. Conceptual Framework and Steps in Impact Pathway
SRT1: Approaches and models for
strengthening innovation
systems, building stakeholder
innovation capacity, and linking
knowledge to
policy action
SRT2: Reducing vulnerability and
managing risk
SRT3: Sustainable intensification
for more productive, profitable and
diversified dryland agriculture with
well-established linkages to
markets
SRT4: Measuring impacts and
cross-regional synthesis

7. Tradeoffs and scale
Markets
Community,
watershed,
region…
Markets
Farm, household, l
ivelihood…
Field, flock, forest
Microbe-plant

8. Key tradeoffs and tools: plant to field scale
Examples
• High and low harvest index (fodder, building material Vs grain)
• Short duration risk avoidance Vs longer duration higher yielding
• Effect of stay green traits in sorghum across environment
Tools
• Detailed crop models that capture interactions between environment
and genotype….and phenotype
e.g. Hammer et al. (2010) uses “….sufficient physiological rigour for complex
phenotypic traits to become emergent properties of the model dynamics.”
[Hammer et al. 2010. J. Exp. Botany 61(8), 2185-2202.]
Microbe-plant

9. Simulating consequences on grain yield- sorghum
Yield consequences reflect trends in field data (e.g. Dalby)
Source: Hammer pers. comm

10. Key tradeoffs and tools: Field to farm scale
Examples:
• Fallow weed control and consequences for soil water at sowing (&
labour tradeoffs)
• Quantifying the riskiness of various intervention strategies (e.g.
fertiliser response x season)
• Comparing decisions around crop type/variety and time of planting
Tools
• Crop-soil models that capture interactions between environment and
genotype (e.g. APSIM, DSSAT)
• Summary models that capture model output statically (e.g. IAT)
• Farm level models that capture interactions (e.g. APSFARM, NUANCES)

11. Effect of variations in PAW and seeding opportunity on
percentage of modelled yields – South Australian wheat
belt Upper tercile (white)
Middle tercile (grey)
Lower tercile (black)
Planting opportunity: Early Late

12. Fertilizer response in extra bags grain for one bag
applied AN (15 kg N/ha)
a b
Sowing window from 1 Nov 1 Dec
d c
Plant population (/m2) 2.0 3.5 2.0 3.5
e
Weed control good poor good poor good poor good poor
Soil Depth Soil fertility
Shallow (50 cm) low 10 1 3 0 8 1 2 0
mod 9 3 9 1 7 3 6 1
high 7 4 8 2 5 3 5 1
Medium (100 cm) low 17 5 14 1 15 4 11 0
mod 11 6 16 5 11 7 15 5
high 9 6 14 6 8 7 13 6
Deep (>150 cm) low 16 6 17 2 15 0 15 2
mod 11 7 17 7 10 8 15 8
high 8 6 14 8 8 6 13 9
very low risk (one year in 10)
medium risk (one year in 5)
high risk situations

13. Key tradeoffs and tools: Farm to
watershed or regional scales…
Examples:
• Impacts of soil conservation measures (buffers, etc.) in watershed to
national level erosion assessments (e.g. USDA)
• Impacts of widely adopted agronomic interventions on watershed
processes (e.g. Lake Tana in NW Ethiopia).
Tools
• SWAT-APEX-EPIC (http://swat.tamu.edu/ http://apex.tamu.edu/)
• Bio-economic modelling frameworks (farm to regional) e.g. or
Integrated Agricultural Assessment Tools (IAAT) (CIRAD & CIHEAM)

14. • Hydrologic analysis showed sufficient water for dry season irrigation
• Crop yields responded strongly to N, dry season irrigation, improved
varieties
• Major environmental consequences due to increased yields - reductions
in soil erosion and sedimentation

15. Conclusions
This CRP has aims at agro-ecosystems where:
(i) systems are highly vulnerable ….increase resilience to shocks
(ii) systems where some sustainable intensification options are available
Mixed (crop-livestock) farming systems are dominant and therefore key tradeoffs
at field/farm level include enterprise selection/ labour/ residues/ investment/
climate risk management…
Tools available (defined largely by the interested partners):
• pasture-tree-crop-soil modelling (CSIRO, APSRU group, Australia)
• whole farm/watershed management (Texas A&M, USA)
• Animal (CIRAD) and whole farm to regional economic modelling (CIHEAM-
Montpellier)
• Underpinned by efforts to develop research methods support (Reading
University)
A community of practice of model expertise underpinning many of
the CRP1.1 activities.
Systems analysis is not just about the tools, its also how they are applied (e.g.
Whitbread et al 2010, Ag. Systems show 4 distinct modes of use in SSA)

16. Dryland Systems focuses on two
agro-ecosystems (SRT2 and SRT3)