Around 30% of the main global cereal crops, including rice and wheat, may have reached their maximum possible crop yield potential in farmer’s fields, reports research published this week in Nature Communications. Yields of these crops have recently displayed an abrupt decrease or have plateaued. Future projections that would ensure global food security are, however, typically based upon a constant increase in yield; a trend that this research now suggests may not be possible.

Estimations of future global food production and its ability to meet the dietary needs of a growing human population have been thus far mostly based on projections of historical trends. Past trends have, however, been dominated by the rapid adoption of new technologies - sometimes one-time innovations - which allowed for an increase in crop production. As a result, optimistic future projections have been formed.

Kenneth Cassman and colleagues characterize past yield trends for cereal, oil, sugar, fibre, pulses, tuber, root crops, rice, wheat and maize, in countries with greatest cereal production and provide evidence against a projected scenario of crop yield increase. Their data suggest that the rate of yield gain has recently decreased or stopped for one or more of the major cereals in many of the most intensively cropped areas of the world, including eastern Asia, north-western Europe and the US. They calculate that the stagnation in yield gain affects around 33% of the global rice and 27% of the global wheat production. In China the increase in crop yields in wheat has remained constant, but maize yield increase has decreased by 64% for the period 2010-2011 relative to the years 2002-2003. This decrease has occurred despite an increase in investment in agricultural research and development, education, and infrastructure, suggesting that in many areas a maximum potential of yield production may have been reached.

The authors report that sustaining further yield gain would likely require fine tuning of many different factors in the production of crops. But this is often difficult to achieve in farmer’s fields and the associated marginal costs, labour requirements, risks, and environmental impacts may outweigh the benefits.