Photo: Getty/David McNew

The world may be nearing the upper limits of agricultural production, raising questions about how we will feed a more crowded planet.

US researchers say yields of about 30 per cent of crops, including rice and wheat, have decreased abruptly or have plateaued in recent years.

Most future projections that would ensure global food security are typically based upon a constant increase in yield.

However, this new research reported in Nature Communications, suggests this may not be possible.

Past trends have been dominated by the rapid adoption of new technologies which allowed for an increase in crop production.

Kenneth Cassman and colleagues at the University of Nebraska characterise past yield trends for cereal, oil, sugar, fibre, pulses, tuber, root crops, rice, wheat and maize, as evidence against a projected scenario of crop yield increase.

Their data suggest 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 research was published in Nature Communications.

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