1. GYGA-OFRA collaboration
01/04/2017
GYGA-OFRA collaboration
Climate-Soil-Cropping system extrapolation domains
Lieven Claessens
OFRA inception workshop, Nairobi, 26/11/13

2. Global Yield Gap Atlas (GYGA) www.yieldgap.org
University of Nebraska (UNL)
Wageningen University & Alterra
Kenneth Cassman
Patricio Grassini
Martin van Ittersum
Lenny van Bussel
Joost Wolf
Justin van Wart
Haishun Yang
Hendrik Boogaard
Hugo de Groot
Daniel van Kraalingen
Regional coordinators and partners
Funding sources:
Gates Foundation (SSA, S Asia)
UNL Water for Food Institute (N & S Amer)
USAID (N Africa, Middle East)
Lieven Claessens (ICRISAT)
Kazuki Saito (Africa Rice)

3. Global Yield Gap Atlas: www.yieldgap.org
EUROPE:
- ca. 30 countries:

4. 70%
30%
Can agriculture reliably and sustainably provision an urban population of 6+ billion?
Source: 4

5. Why yield gap analysis?
Currently not possible to provide reliable answers to critical questions of policy makers and R&D organizations:
Food production potential for a region or country (on existing farm land, if farmers adopted best management practices)?
Will it be possible for country/region X to be self-sufficient in food production by 2030 or 2050? Under different climate and socio-economic scenarios?
When and where can we predict crop yields to stagnate because they reach biophysical yield ceilings?
What are the causes of yield gaps and how to overcome them? How can we target options for sustainable intensification?
What are the regions to target experimentation and what are extrapolation domains?

6. Previous yield gap studies
Regional studies:
crop growth models, experiments, best management practices
local relevance, but not possible to compare them mutually, due to inconsistent concepts and methods
Global studies:
statistical procedures or generic crop growth models
consistent, but generally too coarse, lacking local detail and hence agronomic relevance
van Ittersum et al., Field Crops Research 143, 2013

7. Motivation and focus on Sub-Saharan Africa
01/04/2017
GYGA aspirations:
Food and water security for a population exceeding 9 billion by 2050 while conserving natural resources = high(er) and stable yields on currently used arable land suitable for sustainable intensification
Especially relevant for smallholder systems in SSA:
80% of food produced in SSA from smallholder agriculture (IFAD, 2011)
Food production not keeping pace with population growth
More to food security than production alone (distribution, demand, waste, governance, population)…
Major options in SSA for improving productivity and environmental outputs simultaneously

8. Sustainable intensification in SSA smallholder context
01/04/2017
Smallholder production systems extremely diverse:
Agro-ecology (climate, soil, landform)
Socio-economic conditions (e.g. access to land, labour, inputs, markets)
No ‘silver bullet’ intervention for sustainable intensification!
Rather ‘best fit’ approach from basket of options (Giller et al., 2011)

9. Examples from the basket of options
01/04/2017
Integrated Soil Fertility Management (Tittonell & Giller, 2013; Giller et al., 2011; Khan et al., 2010; Vanlauwe et al., 2010; Altieri et al., 2012)
Crop-livestock integration, dual-purpose crops (Valbuena et al., 2012; Homann et al.; Claessens et al., 2009)
Fertilizer micro-dosing
Seed technologies (hybrids, seed priming,…)
New crops and crop rotations/combinations/intercropping (e.g. banana-coffee (van Asten) sorghum-legumes (Atakos et al., 2013)
Small scale irrigation/mechanization
Soil water management (e.g. tied ridges, terracing)
Conservation agriculture (e.g. mulching, zero-tillage, rotation with legume,…)
Agroforestry

10. Importance of soils for SI in SSA
01/04/2017
Degraded and poorly responsive soils cover large parts of SSA and represent the majority of poor farmers’ fields
Where natural resources are degraded, yield gaps become poverty traps (Tittonell & Giller, 2013)
African form of sustainable intensification needs to be targeted to ag. system’s responsiveness to limited amounts of ‘intervention’ (inputs, technologies from basket, policies)

11. Proposed index for soil suitability/responsiveness
01/04/2017
‘Inherent’ soil properties contributing to yield potential:
WHC (texture, bulk density, infiltration, soil temperature)
Rooting depth not limiting
Slope (runoff/erosion) not limiting
Properties that are, in principle, amenable to modification through management and inputs:
Soil fertility/health (SOM of topsoil as proxy?)
Measure of physical and chemical degradation + (ir)reversibility
pH, salinity, toxicity,…
Classify each (quantified) property and combine in (weighted) matrix for Soil Suitability Index

12. Possible sources of soil data
01/04/2017
ISRIC-AfSIS suitability/constraints maps
Soil rooting conditions
Soil nutrient availability and retention capacity
Soil salinity, toxicity, workability
AfSIS 1km soil property maps of Africa:
Texture
SOC pH
CEC
Bulk Density
AfSIS Land Degradation Surveillance Framework
60 sentinel sites, 19,200 soil samples,….

13. 01/04/2017

14. 01/04/2017

15. ISRIC/AfSIS: 3D regression kriging with
~12,000 legacy profiles (including ISRIC-WISE)
01/04/2017
1km resolution
SOC pH
Texture
CEC
Bulk Density
WRB groups

16. Yield gap analysis: ‘bottom-up’ protocol
van Wart et al, 2013
Yield gap analysis: ‘bottom-up’ protocol
Climate zones
Crop-specific harvested areas
Weather station buffer zones
Soil types and cropping systems
Crop model simulations
Actual yields
Yield gaps
Ewert et al., 2011
Aggregation and upscaling

17. GYGA upscaling method CZ2 CZ1 CZ3 ST1 ST2 CZ4 ST3 ST4
01/04/2017
20%
15%
CZ2
CZ1 5%
CZ3
25% 5%
ST1
30%
CZ4
ST2
ST3
Select soil type in harvested area as near to the selected weather stations as possible
In case two soil types have similar dominant level, these two will be selected
ST4

18. Linking Soil Suitability with Yield Gap Assessment
01/04/2017
GYGA yield gap assessment will give indication about yield gaps and stability of potential/water limited yield over time
Overlaying soil suitability index with yield gaps will identify zones where (lack of) soil quality can explain a large part of the yield gap:
High soil suitability with large (stable) yield gap
= high potential for sustainable intensification (productivity side)

19. Conclusions
01/04/2017
Targeting sustainable intensification options is and important component of global future security studies
Focus on soil suitability especially relevant for smallholder systems in SSA
New sources of high resolution soil data can help in constructing a soil suitability index tuned towards the basket of intervention/adaptation options
Combined with GYGA approaches to yield gap assessment, ‘best bet’ areas/systems for sustainable intensification can be identified: extrapolation domains for OFRA

20. 01/04/2017
THANKS!