Maize is a globally important crop used for food, biofuel and livestock feed, with approximately 40% of global production in the US Corn Belt. In recent years, maize production has been threatened by climate change, primarily related to greater water stress arising from exposure to extreme heat and reduced water availability. Adaptation measures have therefore been adopted to minimize the impacts of drought on crop yields — including the use of drought-tolerant species — but their effectiveness remains difficult to assess.
David Lobell from Stanford University, USA, and colleagues, use sub-county soil maps and satellite-derived yield estimates to assess how maize yield sensitivity to weather is changing across the US Corn Belt. Maize losses owing to drought conditions have increased, signifying greater yield sensitivity. In particular, a 100 mm increase in plant available water storage is related to a 0.23 t ha−1 yield benefit in 1999 but 0.36 t ha−1 in 2018. Averaged across all nine US Corn Belt states, these changes reflect a 55% increase in yield sensitivity to water storage, but larger increases are apparent in drier states such as Missouri, South Dakota and Illinois. Increased water needs arising from greater sowing density might be partially responsible.
Thus, while new agronomic practices and technologies have allowed maize yields to increase substantially in good growing conditions, it is evident that they are unable to limit the impact of climate shocks such as drought. Further adaptation efforts are therefore required to maintain maize yields amidst growing global demand, while minimizing the effects of drought.
Lobell, D. B. et al. Changes in the drought sensitivity of US maize yields. Nat. Food https://doi.org/10.1038/s43016-020-00165-w (2020)
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Simpkins, G. Maize sensitivity to drought. Nat Rev Earth Environ 1, 625 (2020). https://doi.org/10.1038/s43017-020-00117-9