2 Global Yield Gap Atlas (GYGA) www.yieldgap.org University of Nebraska (UNL)Wageningen University & AlterraKenneth CassmanPatricio GrassiniMartin van IttersumLenny van BusselJoost WolfJustin van WartHaishun YangHendrik BoogaardHugo de GrootDaniel van KraalingenRegional coordinators and partnersFunding 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 practiceslocal relevance, but not possible to compare them mutually, due to inconsistent concepts and methodsGlobal studies:statistical procedures or generic crop growth modelsconsistent, but generally too coarse, lacking local detail and hence agronomic relevancevan Ittersum et al., Field Crops Research 143, 2013
7 Motivation and focus on Sub-Saharan Africa 01/04/2017GYGA 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 intensificationEspecially relevant for smallholder systems in SSA:80% of food produced in SSA from smallholder agriculture (IFAD, 2011)Food production not keeping pace with population growthMore 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 01/04/2017Smallholder 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 01/04/2017Integrated 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-dosingSeed 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/mechanizationSoil 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 01/04/2017Degraded and poorly responsive soils cover large parts of SSA and represent the majority of poor farmers’ fieldsWhere 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 limitingSlope (runoff/erosion) not limitingProperties 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)reversibilitypH, salinity, toxicity,…Classify each (quantified) property and combine in (weighted) matrix for Soil Suitability Index
12 Possible sources of soil data 01/04/2017ISRIC-AfSIS suitability/constraints mapsSoil rooting conditionsSoil nutrient availability and retention capacitySoil salinity, toxicity, workabilityAfSIS 1km soil property maps of Africa:TextureSOCpHCECBulk DensityAfSIS Land Degradation Surveillance Framework60 sentinel sites, 19,200 soil samples,….
15 ISRIC/AfSIS: 3D regression kriging with ~12,000 legacy profiles (including ISRIC-WISE)01/04/20171km resolutionSOCpHTextureCECBulk DensityWRB groups
16 Yield gap analysis: ‘bottom-up’ protocol van Wart et al, 2013Yield gap analysis: ‘bottom-up’ protocolClimate zonesCrop-specific harvested areasWeather station buffer zonesSoil types and cropping systemsCrop model simulationsActual yieldsYield gapsEwert et al., 2011Aggregation and upscaling
17 GYGA upscaling method CZ2 CZ1 CZ3 ST1 ST2 CZ4 ST3 ST4 01/04/201720%15%CZ2CZ15%CZ325%5%ST130%CZ4ST2ST3Select soil type in harvested area as near to the selected weather stations as possibleIn case two soil types have similar dominant level, these two will be selectedST4
18 Linking Soil Suitability with Yield Gap Assessment 01/04/2017GYGA yield gap assessment will give indication about yield gaps and stability of potential/water limited yield over timeOverlaying 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 Conclusions01/04/2017Targeting sustainable intensification options is and important component of global future security studiesFocus on soil suitability especially relevant for smallholder systems in SSANew sources of high resolution soil data can help in constructing a soil suitability index tuned towards the basket of intervention/adaptation optionsCombined with GYGA approaches to yield gap assessment, ‘best bet’ areas/systems for sustainable intensification can be identified: extrapolation domains for OFRA