Yield gap analysis has become popular to assess how much and where food production can be increased on existing land. It is also helpful in identifying an acceptable compromise between yield, resource use efficiency and local emissions of nutrients or crop protection agents, as resource use efficiencies tend to decrease once yields exceed a certain percentage of potential yields (e.g. 80%). The literature provides many examples of global and regional studies with yield gap analyses. The global ones are appealing because of their consistent use of one method and global databases, but they lack local or even regional agronomic rigour. Regional studies use a range of different methodologies and are therefore hard to compare mutually.
In the Global Yield Gap Atlas (www.yieldgap.org) yield gaps of all key agricultural commodities are estimated for all food producing countries, using a global protocol. The protocol is always applied with local data on weather, soils, cropping systems and actual farm yields, and the results are evaluated with local experts.
This paper presents results for an initial 35 countries covering, respectively, c.60%, 58%, and 35% of global rice, maize, and wheat production. It then demonstrates how results can be used to explore options for future self-sufficiency in cereal production in sub-Saharan Africa, the sub-continent with the fastest increase in cereal demand until 2050. Next, the paper presents a method that enables yield gap analysis to be used for the prioritisation of research and development investments. Once yield gaps have been assessed, a key follow up question is why yield gaps exist: what are their underlying biophysical and socio-economic causes? To this end it is helpful to decompose yield gaps into efficiency, resource and technology gaps. Finally, yield gaps can be usefully translated into nutrient (uptake and application) gaps. These indicate by how much the balanced nutrition of crops should increase to realise a certain percentage of yield gap closure.
Martin K. van Ittersum, Sander C. de Vries, Plant Production Systems group, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands.
Pepijn A.J. van Oort, Africa Rice Center, 01 BP 2031, Cotonou, Benin and Centre for Crop Systems Analysis (CSA), Wageningen University, PO Box 430, 6700 AK Wageningen, The Netherlands.
P. Grassini, Department of Agronomy and Horticulture, University of Nebraska-Lincoln, PO Box 830915, Lincoln, NE 68583-0915, USA.
20 pages, 4 figures, 2 tables, 30 references